.Q_ ..:..’ gii‘fl 95‘ 59 v -.; 3.: - .'; Angie-2‘ (‘5'- I- .9 a -o J 1.\ ' {.14- .rJC .2 '— '..‘- m. 5.9 1-7??? ' 5;. . ( U ".E a. ' ' -- _ ‘ . _ AT LE". £311“. ‘ '- : ' .. ,5! .J‘.‘ _A _ . . - - n.‘:’“ ‘51; ‘ul‘b' '''''' ’l' Maw-'wm n—q -:‘-:y) - ‘ :3 ' _ :" rh; :t;::i’ g“ 2:: Lu'p‘lék 3“? 514%..) u ,Q l 1 a ill!fill/II/lllIH/IW/I/lflll/II/fill/I/ll/l/fI/IH/f/Ill/ll 3 1293 10065 8792 This is to certify that the thesis entitled . ECOLOGICAL STUDIES ON THE SPRINGHARE PEDETE’S CAPENSI S IN BOTSWANA presented by Thomas Michael Butynski has been accepted towards fulfi of the requirements for Ph.D. degree in Wildlife Ecology \ \ Ilment 6; 4 first/sq. \‘2€\ Major professor Date ydrlsfwf / 9 74¢ 0-7639 ECOLOGICAL STUDIES ON THE SPRINGHARE PEDETES CAPENSIS IN BOTSWANA By Thomas Michael Butynski A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Fisheries and Widlife 1978 U if. 3 ABSTRACT ECOLOGICAL STUDIES ON THE SPRINGHARE PEDETES CAPEWSIS IN BOTSWANA By Thomas Michael Butynski The ecology of the springhare Pedetes capensis was studied in Botswana (August 1971 - August 1974). A mean 24.2 i 1.6 springhares were collected monthly from September 1971 through July 1973. Data on 560 juveniles and adults, and 153 foetuses were analyzed. Digging behavior, time of burrow excavation, and function and location of springhare burrows are discussed. Grass composition was in- fluenced by burrowing activity. The overall pattern of three excavated burrows was circular with most entrances on the periphery of the system; mean depth 8 78cm, mean length - 42.1m, greatest depth - 122cm, tunnel height . 17-25cm, tunnel width 3 10-23cm, and mean number of entrances = 9.3. Both temporary and permanent earthen plugs were present. No cham— bers, side-pockets, blind tunnels, food, or nesting materials were found in the burrows. Pelages of juvenile and adult springhares are described. Molt pat- tern is of the caudad type in both juvenile and adult molts. Overall, 64% of juveniles and 192 of adults were in molt. Time of juvenile molt was associated with body size and age. Incidence of juvenile molt was highest during the wet season, but this molt occurred in all months. Peak months for adult molt were December and January. No springhares were in adult molt during July or August. Adult molt showed significant positive correlations with monthly total rainfall, mean air temperature, mean forage protein, and day length at mid-month. No sexual dimorphism was found for pelage, molt pattern, or time of molt. Lactation appeared to hinder molt. Springhares were moikocous. Seventy-six percent of adult females were pregnant, 46% were lactating, and only 4% were neither pregnant nor lactating. The male to female ratio was 51:49, and the juvenile to adult ratio was 28:72. No seasonal peaks in reproductive effort were noted. The reproductive strategy of the springhare is considered. Equations are provided describing the rate of growth for several body parts of the springhare flyatus relative to body weight. Changes in external morphology of the foetus are described. Both absolute birth weight (252g) and birth weight relative to weight of the mother (8.3%) were lower than predicted for a mammal of this body size. Growth of the reproductive tract of male springhares is described relative to dried eye lens weight. Spermatogenesis was exhibited by 72% of all males collected. A testis weight of 2.3g, dried baculum weight of 41mg, and seminiferous tubule diameter of ll7um can be used to separate prepubertal from postpubertal males. Fecundity of the male was not associated with monthly total rainfall, mean air temperature, or day length at mid-month. Seasonal atrophy or senescence of the male repro- ductive tract did not occur. Reproductive effort in the male springhare appeared to be constant throughout the year. Linear and quadratic equations are presented to describe the growth rates of 29 body parts of male and female springhares relative to dried eye lens weight. Allometric equations based on body weight are used for intraspecific and interspecific comparisons of the relative growth rates of various body parts. Incidence and intensity of the stomach nematode, Physaloptera capensis, in relation to age, sex, reproductive status, physical condition, density, and habitat of its host, the springhare, were examined. Mean number of worms per host was 8.3,and 34% of all springhares were parasitized. Adults, females, and lactating females showed significantly heavier infections than juveniles, males, and non-lactating females, respectively. Infection was directly associated with the amount of grass cover, but independent of the density and physical condition of the host. Possible causes of differences in rates of infection among springhares of different reproductive status are suggested. The regulation of Physaloptera capensis populations is discussed. Dedicated to my parents ii ACKNOWLEDGEMENTS I wish to acknowledge the cooperation and financial assistance of the Botswana Department of Wildlife, National Parks and Tourism, the United States Peace Corps, and Michigan State University. My principle debt is to the members of my doctoral committee, Drs. George Petrides, Rollin Baker, John King, Duane Ullrey and Clarence McNabb for their keen interest, numerous helpful suggestions, and con- structive reviews of the thesis manuscript. The high respect I hold for these men cannot be expressed. I especially thank Dr. George Petrides, my major professor and committee chairperson, for his guidance and en- couragement. Warmest thanks are extended to my friends through whose association so much was accomplished, experienced and learned. "Kutswe" Aaron, Robert Armstronge III, Cassie Boggs, Jeffery Dawson, Dennis and Anita Longenecker, Gregory Mann, Derek Massey, Rosanna Mattingly, Susan McMahon, John Sihvonen, and Carol Fisher ang require special mention in this con- text . This work would not have been completed without the help of the staff of the Botswana Department of Wildlife, National Parks and Tourism. I am especially grateful to Alec Campbell, former Director, Dr. Wblfgang von Richter, former FAO Wildlife Ecologist, and Lindsey Birch, former Chief Game Warden, for their support and direction through several dif- ficult periods. I am indebted to Dr. Raey Smithers and the National MMseums of iii Rhodesia for original data on Pedetes, to Dr. John Hanks at the Univer- sity of Natal for examining reproductive materials, to Andrew Anderson, former Director, and 1.3.8. Dipheko, Director, Botswana Meteorological Services, for weather data, to Douglas Legg, Botswana Agricultural Ex- periment Station, for nutritional analysis of stomach contents, to Drs. Richard Dukelow and Thomas Kuehl, Muchigan State University Endocrine Research Unit, for much of the computer analysis, and to Dr. Jack Falconer, Director of Botswana Veterinary Services, Dr. Paco Boroso, former Director, and Dr. Victor Simpson, Director of the Botswana Veterinary Research Laboratory, for laboratory space and equipment. iv LIST OF TABLES. . . . LIST OF FIGURES . . . INTRODUCTION. . . . . STUDY AREAS . . . . . MATERIALS AND METHODS SECTION I. BURROW STRUCTURE SPRINGHARE OF CONTENTS FOSSORIAL Int rOduc t ion 0 O O O O O O O O O O 0 Materials and Methods . . . . . . . Results and Discussion. . . . . . . External Morphology. . . . . . . Location of Burrows. . . . . . . Digging Behavior . . . . . . . . Description of the Burrow System Time of Excavation . . . . . . . Number of Springhares per Burrow Functions of the Burrow. . . . . Effect of Burrows on Vegetation. PELAGE AND MDLT IN THE SPRINGHARE. . Introduction. . . . . . . . . . . . Materials and Methods . . . . . . . Re8u1t8 O O O O O O O I O O O O O O Pelage Stages. . . . . . . . . . Molt Pattern . . . . . . . . . . Age at Molt. . . . . . . . . . Time Required to Und rtake Molt. Relationship between the Time of Environmental Factors . . . . Discussion. . . . . . . . . . . . . REPRODUCTIVE ECOLOGY OF THE SPRINGHARE 0 Introduction. . . . . . . . . . . . MethOds O O O O O O O O O O I O O O Page viii xi 12 l4 l4 14 15 15 15 15 16 26 26 26 29 32 32 32 33 33 34 36 37 38 39 44 44 45 Page Results . . . . . . . . . . . . . . . . . . . . 45 Juvenile : Adult Ratios and Sexual Maturity. 45 Sex Ratios . . . . . . . . . . . . . . . . . 47 Vaginal Plugs. . . . . . . . . . . . . . . . 47 Pregnancy Rates. . . . . . . . . . . . . . . 47 Litter Size and Implantation Sites . . . . . 48 Foetal Mbrtality . . . . . . . . . . . . . . 49 Lactation and Weaning. . . . . . . . . . . . 49 Breeding Season. . . . . . . . . . . . . . . 50 Discussion. . . . . . . . . . . . . . . . . . . 52 Population Regulation. . . . . . . . . . . . 52 Reproductive Strategy. . . . . . . . . . . . 56 IV. GROWTH AND DEVELOPMENT OF THE FOETAL SPRINGHARE. 59 Introduction. . . . . . . . . . . . . . . . . . 59 Materials and Methods . . . . . . . . . . . . . 59 Results and Discussion. . . . . . . . . . . . . 60 Size and State of Development at Birth . . . 60 Estimating Foetal Age. . . . . . . . . . . . 61 External Measurements. . . . . . . . . . . . 65 External Morphology. . . . . . . . . . . . . 69 Foetal vs. Maternal Weight . . . . . . . . . 69 V. REPRODUCTIVE ACTIVITY IN THE MALE SPRINGHARE . . 73 Introduction. . . . . . . . . . . . . . . . . . 73 Materials and Methods . . . . . . . . . . . . . 75 Results and Discussion. . . . . . . . . . . . . 76 Development of the Reproductive Tract. . . . 76 Puberty. . . . . . . . . . . . . . . . . . . 82 Breeding Season. . . . . . . . . . . . . . . 35 VI. BIOMETRIC ANALYSIS OF BODY AND ORGAN GROWTH OF THE JUVENILE AND ADULT SPRINGHARE. . . . . . . . . 88 Introduction. . . . . . . . . . . . . . . . . . 88 Materials and Methods . . . . . . . . . . . . . 88 Results and Discussion. . . . . . . . . . . . . 91 Body Measurements. . . . . . . . . . . . . . 91 Growth Equations . . . . . . . . . . . . . . 99 Instantaneous Growth Rates . . . . . . . . . 102 Patterns of Growth . . . . . . . . . . . . . 102 Relative Organ Weight. . . . . . . . . . 108 Organ Weight Allometric Equations. . . . . . 110 VII. HOST AND ECOLOGICAL ASSOCIATIONS OF THE NEMATODE, PHYSALOPTERA CAPEWSTSQ OF THE SPRINGHARE . . . 117 Introduction. . . . . . . . . . . . . . . . . 117 Life Cycle of Physaloptera capensis . . . . . . 118 vi Page Materials and Methods. . . . . . . . . . . . . . 120 Definitions. . . . . . . . . . . . . . . . . . . 121 Results. . . . . . . . . . . . . . . . . . . . . 122 PhysaZoptera capensis in the Host Stomach. . 122 Frequency Distribution. . . . . . . . . . . . 125 Incidence of Infection. . . . . . . . . . . . 125 Effect of Host Age . . . . . . . . . . . . 125 Effect of Host Reproductive Status . . . . 126 Intensity of Infection. . . . . . . . . . . . 126 Effect of Host Age . . . . . . . . . . . . 126 Effect of Host Reproductive Status . . . . 128 Relationship Between Incidence and Intensity of Infection. . . . . . . . . . . . . . . . 131 Effect of Host Food Intake and Diet . . . . . 131 Effect of Host Physical Condition . . . . . . 132 Effect of Host Density and Habitat. . . . . 134 Seasonal Variation in Incidence and Intensity of Infection. . . . . . . . . . . . . . . . 137 Bimonthly Samples. . . . . . . . . . . . . 137 Combined Bimonthly Samples . . . . . . . 138 Effect of Host Physical Condition. . . . . 141 Discussion . . . . . . . . . . . . . . . . . . . 141 Frequency Distribution. . . . . . 141 Relationship between Incidence and Intensity. 142 Host Resistance . . . . . . . . . . . . . . . 142 Host Susceptibility . . . . . . . . . . . . . 143 Effect of Host Age . . . . . . . . . . 143 Effect of Host Reproductive Status . . . . 144 Effect of Physaloptera capensis on the Host . 147 Effect on Host Fertility . . . . . . . . 147 Effect on Host Physical Condition. . . . . 147 Pathology. . . . . . . . . . . . . . . . 148 Effect of the External Environment. . . . . . 143 Seasonal Variation in Intensity of Infection. 151 Host Density—Dependent Hypothesis . . . . . . 152 Regulation of PhysaZoptera capensis Populations . . . . . . . . . . . . . . . . 154 Bradley's Hypotheses . . . . . . . . . . . 154 Regulation by the Host Population (Hypothesis II). . . . . . . . . . . . . 155 Regulation by the Host Individual (Hypothesis III) . . . . . . . . . . . . 155 Transmission-Regulated Infection (Hypothesis 1) . . . . . . . . . . . . . 155 SUMMARY. . . . . . . . . . . . . . . . . . . . . . . . . . . 157 RECOMMENDATIONS. . . . . . . . . . . . . . . . . . . . . . 162 LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . 163 vii Table Table Table Table Table Table Table Table Table Table Table 10. 11. LIST OF TABLES Data on three typical springhare burrows. See text for details and definitions. . . . . . . . . . . . . Cited and probable predators on the springhare in Botswana . . . . . . . . . . . . . . . . . . . Percentage composition of grasses occurring in each of three zones around 36 springhare burrow systems in the Central Kalahari Bush Savannah . . . . . . . Monthly distribution of springhares in juvenile and adult molts in Botswana and Rhodesia, and monthly values for total rainfall, mean air temperature, mean forage protein, and mid-month day length. . Summary of an analysis of variance used to test the interaction between the size of the body parts of springhares and month of collection. . . . . . Means and standard deviations 8.0. of growth parameters for male springhare foetuses for each 20g category Of body weight 0 O O O O O O O O O O O O O O I O O 0 Means and standard deviations 3.0. of growth parameters for female springhare foetuses for each 20g category of body weight . . . . . . . . . . . . . . . . . . . Coefficient constants a and b, and correlation coef- ficients r for the linear regression of five body measurements Y of male and female springhares on body weight X in grams. Size of samples as in Tables 6 and 7 . . . . . . . . . . . . . . . . Pattern of growth and development in the foetal springhare O O O O O O O O O O O O I O O O O O O O 0 Means 5, coefficients of variation C.V., and sample size n for 12 measurements from the reproductive tract of the male springhare as they relate to dried eye lens weight. . . . . . . . . . . . . . . . Summary of spermatogenic activity of 264 male spring- hares as it relates to measurements of six body parts. See text for explanation. Size of samples as in Table 10 . . . . . . . . . . . . . . . . . . . viii Page 23 28 31 4O 51 66 67 68 7O 77 84 Table Table Table Table Table Table Table Table Table 12. 13. 14. 15. 16. 17. 18. 19. 20. Page Monthly values for mean testis weight and semini- ferous tubule diameter of adult springhares (eye lens weight > 350mg) relative to monthly total rainfall, mean air temperature, mean forage protein and mid-month day length . . . . . . . . . . 86 Means and standard deviations 8.0. of growth parameters for male springhares in each 50mg category of dried lens weight from 150-649 mg. . . . 92 Means and standard deviations 8.0. of growth parameters for female springhares in each 50mg category of dried eye lens weight from 150— 649mg. . . . . . . . . . . . . . . . . . . . . . . . 96 Coefficient constants a and b, and correlation coefficients r for the linear regression of several growth variables Y on dried eye lens weight X (mg) of male and female springhares. Size of samples as in Tables 13 and 14 . . . . . . . . . . . . . . . . . . . . . . . 100 Coefficient constants a, b and b , and correlation coefficients r for the quadratic regression of several growth variables Y on dried eye lens weight X (mg) of male and female springhares. Size of samples as in Tables 13 and 14 . . . . . . . 101 Comparison of male-female and right side-left side absolute mean values for various body parts of springhares. Size of samples as in Tables 13 and 14 . . . . . . . . . . . . . . . . . . . . . . . 107 Organ weights of male and female springhares expressed as a percentage of body weight (g organ weight/100g body weight) for three different categories of dried eye lens weight. Size of samples as in Tables 13 and 14 . . . . . . . . . . . 109 Comparisons of relative kidney, heart, and liver weights of adult springhares and ten other mammalian species of similar body weight . . . . . . 111 Predicted and observed heart, liver, and kidney weights for male and female springhares in the 500-549mg category of eye lens weight. Pre- dictive values were derived from the organ weight allometric formulas for mammals in general (Brody 1945) . . . . . . . . . . . . . . . . 112 ix Table Table Table Table Table Table 21. 22. 23. 24. 25. 26. Allometric equations of the form Y 3 aXb where X is the body weight (kg). Equations predict the length or weight of various body parts Y ofjuvenile and adult springhares (150—600mg lens weight). Equations were derived from the mean values for each 50mg category of eye lens weight as presented in Tables 13 and 14 . . . . . . . . . . . . . . . . Allometric equations of the form Y 3 aXb where X is the body weight (kg). Comparison of the allometric constant b for kidney, heart, and liver weights Y of mature male and female springhares, mature mammals in general, and mature primates in general. . . . . . . . . . . Incidence and intensity of Physaloptera capensis in each reproductive class of springhares. Number of springhares harboring >' 50 and > 100 worms and the mean wet weight of the stomach contents are also given. See text for defini- tions . . . . . . . . . . . . . . . . . . . . . Incidence and intensity of Physaloptera capensis among springhares of various reproductive status and physical condition (kidney fat). See text for definitions . . . . . . . . . . . . . . . . Description of seven springhare habitats during the dry season and the incidence and intensity of PhysaZoptera capensis in springhares collected from each. Correlation coefficients r and their probabilities indicate the degree of association between each of four habitat parameters and in- cidence and intensity of worms. Sample size equals 333. See text for definitions . . . . . . Bimonthly incidence and intensity of Physaloptera capensis in male and female springhares. Values for several environmental parameters and physical condition indexes of the host are also provided. See text for definitions. . . . . . . . . . . . . . Page 113 115 127 133 135 139 Figure Figure Figure Figure Figure LIST OF FIGURES The (a) adult and (b) newborn springhare Pedetes capensis. . . . . . . . . . . . . . . . . . . Map of the Republic of Botswana . . . . . . . . . . . . Aerial view of a typical pan on the Kalahari Study Area. Note the absence of woody vegetation on the pan surface and the scattered shrubs in the bush savannah. The dense ring of vegetation forming the perimeter of the pan is comprised primarily of the shrubs Acacia meZZifera, Gatophractes aZexandri and Rhigozum brevispinosum . . Vegetation typical of various habitats during the end of the dry season (August-October). (a) Undisturbed Southern and Central Kalahari Bush Savannah (East Savannah & West Savannah Habitats). Dominant grasses are Schmidtia pappophoroides, Eragrostis Zehmanniana and Aristida unipZumis. Dominent woody plants are Grewia fiava, Acacia giraffae, Lonchocarpus neZsii, Terminalia sericea and Acacia meZZifera. (b) Surface of an undisturbed pan (East Pans & West Pans Habitats). Dominant grass species are Sporobolus iocZados, Ehneapogon devauxii and Tragus berteronianus. Acacia meZZifera occurs in scattered, dense clumps on some pans and is the only woody species commonly found on the surface of the pan. (c) Degraded open woodland which is dominated by Gynodon dactylon during the wet season. During the dry season C. dactylon is present only in the form of rhizomes and thus is not visible in the photo (River Bank Cynodbn dactylon Habitat). (d) Degraded Arid Sweet Bush- veld (Metsemotlahaba Open Woodland & Zeerust Road Open Woodland Habitats). Dominant grass species are Ercgrostis rigidior, Erogrostis Zehmanniana, Aristida barbicolis and Urochloa spp., and the primary woody species are Cbmbretum apiculatum, Basia aZbitrunca, Lonchocarpus neZsii and Acacia tortilis . . . . . . . . . . . . . . . . . . . Schematic drawing of springhare Burrow System One as seen from above. Open circles represent mound holes and solid circles represent clean holes . xi 17 Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Schematic drawing of springhare Burrow System Two as seen from above. Open circles represent mound holes and solid circles represent clean holes . . . . . . . . . . . . . . . . . . . Schematic drawing of springhare Burrow System Three as seen from above. Open circles represent mound holes and solid circles represent clean holes . . . . . . . . . . . . . . . . . . . . . . Progression of the dorsal molt pattern in the springhare. Shaded areas represent new pelage. See text for details. . . . . . . . . . . . . . Relationship between the percentages of springhares in adult molt Y and (a) total rainfall, (b) mean air temperature, (c) mean forage protein, and (d) day length at mid-month during each of twelve consecutive months. Sample sizes as in Table 4. See text for details. . . . . . . . . . . . . . . Graphs of those data indicating that springhares bred dUring all seasons and did not exhibit peaks in reproductive effort. (a) Mean weight of adult male (eye lens weight >350mg) right testis each month with the sample size given at each point. (b) Mean weight of foetuses each month. (c) Percentage of pregnant females in each monthly sample which conceived within 30 days previous to collection. (d) Percentage of adult (enlarged reproductive tracts) females pregnant each month. The sample size given at each point applies also to Figure 10b and can be used to calculate the sample size in Figure lOc . . . . . . . . . . . . . . . . . . Graphs of those data indicating that springhares bred during all seasons and did not exhibit distinct peaks in reproductive effort. (a) Total rainfall for each month in the Kalahari (0—0) and Eastern (O---O) Study Areas. (b) Percentage juveniles each month. The sample size is given at each point and can be used to calculate the sample size in Figure 11c. (c) Mean weight of dried eye lens each month . . . . . . . . . . . . Cube root of the weight of the foetal springhare plotted against age. The linear relationship W = 0.117(t-23) can be used to estimate the age t of the foetal springhare in days for any foetus of known weight W. See text for details . xii Page 19 21 35 41 53 54 63 Figure 13. Figure 14. Figure Figure Figure Figure Figure 19. Figure 20. Figure 21. 15. l6. 17. 18. The relationship among body weight (0, n=98), overall length (A , n=96), and the age of foetal springhares. See text for details. . . . . . . Changes in (a) right testis weight, (b) right testis length and (c) body weight of male springhares relative to dried eye lens weight (range = thin vertical line; mean = horizontal line; standard error ' broad vertical line). Size of sample given above each range. . . . Changes in (a) baculum weight and (b) seminiferous tubule diameter of male springhares relative to dried eye lens weight (range = thin vertical line; mean : horizontal line; standard error = broad vertical line). Size of sample given above each range . . . . . . . . . . . . . . . . . . . . . . Plots of mean seminiferous tubule diameter, dried baculum weight, and right testis length against testis weight for male springhares in each 25mg category of dried eye lens weight. Individual data, not means, were used to calculate the regression equations. Size of samples as in Table 10 . . . . . . . . . . . . . . . . . . . . . . Relationship in the male springhare of dried eye lens weight to mean length of the body (0) and growth rate of the body (‘3 body length (mm)/ £1 50mg lens weight) (0). Trancepts represent one standard deviation. The growth rate curve is based upon a three point floating mean and was fitted by eye. Table 13 gives the size of the sample at each point . . . . . . . . . . . . . . . Relationship in the male springhare of dried eye lens weight to mean length of the right testis (O) and growth rate of the right testis ( [5 testis length (mm)/ 15 50mg lens weight). See Figure 17 for further details. . . . . . . . . . . Size of several body parts of the female springhare relative to dried eye lens weight from 150 to 650mg. Changes in testis weight are also shown. See text for details . . . . . . . . . . . . . . . . . PhysaZoptera capensis on a food bolus from the stomach of the springhare. . . . . . . . . . . . . . . . . . . Frequency distribution of Physaloptera capensis in adult male (O---O) and female (O--O) springhares. n=560, ' xiii Page 64 8O 81 83 103 103 105 119 123 Page Figure 22. Regressions of incidence of Physaloptera capensis on dried eye lens weight (relative age) of springhares. Each point represents the percen- tage incidence of worms among male (0) and female (0) springhares occurring within a 50mg category of eye lens weight. n-560. . . . . . . . . 123 Figure 23. Regression of intensity of Physaloptera capensis on dried eye lens weight (relative age) of springhares. Each point represents the mean intensity of worms among male (0) and female (0) springhares occurring within a 50mg category of eye lens weight. n=560. - - - . - . . . . . . . . . 129 Figure 24. Regression of incidence of Physaloptera capensis on intensity in springhares. Each point represents incidence and mean intensity values of worms among male (0) and female (I) springhares occurring within a 50mg category of eye lens weight. n=560. . . . . . . . . . . . 129 Figure 25. Incidence (a) and mean intensity (b) of Physaloptera capensis in male (O---O) and female (O—-—O) springhares during each of 25 consecutive months. n=560. 136 Figure 26. Relationship between time of year and combined bimonthly values for (a) mean intensity of Physaloptera capensis in male (O---O) and female (O--O) springhares, (b) rainfall (O---O) and temperature (H), and (c) springhare stomach protein (O—--O) and day length (O--O). n=560. See text for definitions. . 140 Figure 27. Variables of the external environment affecting development, survival and transmission of para- sitic terrestrial nematode ova and larvae. Inter- actions thought to be most important in accounting for between-habitat differences in Physaloptera capensis populations are designated by the broad arrows. Feedback and minor interactions are not indicated. See text for details . . . . . . . . . . 149 xiv INTRODUCTION Springhares Pedetes capensis Forster (Figures la,b) are large (3kg), bipedal, saltatorial rodents occurring over much of the southern third of Africa (Coe 1969; Dorst & Dandelot 1970; Kingdon 1974). They are herbi- vorous, strictly nocturnal, and spend the day within a burrow. Springhares are locally abundant, and in some areas they are an im- portant depredator of crops and a source of bush-meat (Smithers 1971; Butynski 1973). The springhare is related neither ancestrally nor collaterally, to other rodents (wood 1962), and its pre-Miocene history is not known (Wood 1974). Until recently, the Family Pedetidae was thought to con- sist of two species, the South African springhare P. capensis and the East African springhare Pedetes sundaster. It is now generally accepted, however, that the Family is monotypic, and that P. surdaster is but a subspecies of P. capensis (Burton & Burton 1970; Meester & Setzer 1971; Kingdon 1974). Despite the wide distribution, abundance, and considerable economic value of the springhare, its ecology has not been studied in detail. This thesis provides data on the following aspects of springhare ecology: pelage and molt; reproductive ecology; reproduction in the male; growth and development of the foetus; body and organ growth of juveniles and adults; and host and ecological associations of the nematode, Physalop- tera capensis Ortlepp. Figure 1. The (a) adult and (b) newborn springhare Pedetes capensis. Figure l (a). Figure l (b). STUDY AREAS Springhares were collected from two study areas in the Republic of Botswana (Figure 2). Both lie at an altitude of about llOOm. The wet season occurs from October through March. Mean monthly maxima and minima air temperatures range from near 37°C and 11°C in January and December, to 27°C and -3°C in June and July. Frosts occur from May to October and may be severe. Diurnal variation in air temperature is greatest during the dry season when it is about 20°C. Mean monthly humidity during the mid-afternoon is about 30% and the annual rate of evaporation is nearly 3m. The Kalahari Study Area was located near the center of the country in the remote Khutswe Game Reserve and the southern portion of the Central Kalahari Game Reserve (latitudes 23o - 240 South and longitudes 24o - 250 East) (Figure 2). Total annual rainfall can vary by 70% from the mean of 400mm. The topography is predominantly flat or gently undulating. The Central Kalahari Bush Savannah (Smithers 1971; Weare & Yalala 1971) consists of scattered shrubs and tall grasses, occurs on loose, yellow-gray, aeolian sands, and covers more than 99% of the area (East Savannah & West Savannah Habitats) (Figure 4a). Widely scattered throughout the region are circular, flat-bottomed, seasonally-flooded depressions called "pans" (Figure 3). These lie 5m or more below the surrounding plain and are associated with fossil drainage systems. The twelve pans sampled on the study area are charac- terized by compact, clayey calcareous soils, bordering sand dune forma- tions, dense, short, grass cover, and paucity of woody vegetation (East .mcmsmuom mo owfieseom o£u mo om: .N ouswwh can—via.- I I I ‘ 1 I ‘ ‘ 1‘ I 8. I. .. 3.3: .393 8 2‘2..- Clo-1.: 2 I: :3»... m in“ «a . .88.»: glue 5313: 33:2.- »32 9.... 1...:- x¢22<>a 82-. («(8 tantra-On 02¢ a¢¢p2uu is. =5: «8: stuns. «I: .8338... 33.33. 5...... guns: 42-: 0.5253: ~33 833 .0... 0.0.88 :38:- Ewan. 2394.. a... Z 2::- 33... . ¢.-I¢~ <2<>>th0 Figure 3. Aerial view of a typical pan on the Kalahari Study Area. Note the absence of woody vegetation on the pan surface and the scattered shrubs in the bush savannah. The dense ring of vegetation forming the perimeter of the pan is comprised primarily of the shrubs Acacia meZZifera, Chtophractes clemandri and Rhigozum brevispinosum. Figure 4. Vegetation typical of various habitats during the end of the dry season (August-October). (a) (b) Undisturbed Southern and Central Kalahari Bush Savannah (East Savannah & West Savannah Habitats). Dominant grasses are Schmidtia pappcphoroides, Eragrostis Zehmanniana and Aristida unipZumis. Dominant woody plants are Grewia fiava, Acacia giraffae, Lonchocarpus neZsii, Terminalia sericea and Acacia meZZifera. Surface of an undisturbed Kalahari pan (East Pans & West Pans Habitat). Dominant grass species are Sporobolus iocZadcs, Ehneapogon devauxii and Tragus berteronianus. Acacia meZZifera occurs in scattered, dense clumps on some pans and is the only woody species commonly found on the surface of the pan. x "' "(V ’/ .,._ 'ML-jpaznwwu... b v 3‘ l Figure 4 (b) . (C) (d) Figure 4 (cont'd.). Degraded open woodland which is dominated by Cynodon dactylon during the wet season. During the dry season 0. DactyZon is present only in the form of rhizomes and thus is not visible in the photo (River Bank Cynodan dactylon Habitat). Degraded Arid Sweet Bushveld (Metsemotlahaba Open Woodland & Zeerust Road Open Woodland Habitats). Dominant grass species are Erogrostis rigidior, Erogrostis Zehmanniana, Aristida barbicolis and Urochloa spp., and the primary woody species are Cbmbretum apicuZatum, Basia aZbitrunca, Lonchocarpus nelsii and Acacia tortilis. 10 Figure 4 (d). 11 Fans & West Pans Habitats) (Figure 4b). Study area pans varied from 0.1- l.0km in diameter. The Kalahari Study Area has received little human influence, the area is undisturbed and a perennial grass cover predominates. Grasses in the bush-savannah are not heavily utilized by wild herbivores and thus persist throughout the year. Grasses on the pens are highly palat- able and, as a result, are nearly completely removed during the dry sea- son. Most of the springhares on the Kalahari Study Area are closely associated with pans. Springhares typically feed on the pan grasses and construct their burrows in the sand dunes, usually within 50m of the edge of the pan. The Eastern Botswana Study Area was located in the southeastern corner of Botswana and consisted of the area within 20km of Gaborone (Latitudes 24o - 250 South and longitudes 25o - 260 East) (Figure 2). Mean annual rainfall is 500mm and the annual rainfall can vary by 30%. Soils are occasionally loose sands (Gynodon dactylon Habitat) (Figure 4c), but compact red, gray, or brown sandy-loams predominate (Metsemotlahaba Open Woodland & Zeerust Road Open Woodland Habitats) (Figure 4d). Vege- tation is classified as Arid Sweet Bushveld (wears & Yalala 1971). Un- like the Kalahari Study Area, the original vegetation has been greatly altered by pastoral and agricultural activity (Campbell & Child 1971). Considerable erosion of the soil has occurred. The original perennial grass cover has been largely replaced by annual grasses and bush. A good grass cover persists during the wet season but the area is nearly devoid of grass during the dry season. General descriptions of the vegetation on the two study areas are offered by Smithers (1971), Van Rensburg (1971), Weare (1971), Butynski (1975), and Dawson and Butynski (1975). MATERIALS AND METHODS Springhares were located at night with the aid of a spotlamp con- nected to a lZ—volt truck battery and shot with a 12-gauge shotgun. An attempt was made to collect all springhares encountered. The sampling method is assumed to have been random as there was no evidence to suggest than any sex, age, or reproductive class was differentially susceptible to collection. A total of 319 springhares were collected on the Kalahari Study Area and 241 on the Eastern Study Area. The mean monthly sample size from September 1971 through July 1973 for both study areas combined was 24.2 i 1.6 springhares. In addition, three springhares were collected in August 1971 and two in August 1973. One hundred and fifty-three foetuses were present among females collected. Since springhares first left the burrow when they attained a body weight of approximately 1.3kg, only individuals of this size and larger were susceptible to collection. Weaning occurred soon after springhares first emerged from their burrows (Section Three). The sample upon which the present paper is based consisted, therefore, only of weaned and a few nearly-weaned springhares. Springhares were sexed and females checked for lactation immediately after collection. Eyes were removed and fixed in 10% formal saline within three hours of death. Specimens were either immediately placed in cold storage and frozen, or left out to cool overnight, placed in an icebox the following morning and then transported to cold storage. Fixed eye lenses were removed from the eyes and placed in a con- vection drying oven. After drying to a constant weight, the lenses were 12 l3 weighed to the nearest milligram. Eye lens weights referred to in this paper are for one lens as derived from the mean of the two dried eye len- ses from each springhare. Since known age materials were not available there was no way to establish the chronological age of the animals used in this study. There- fore, dried eye lens weight is used as an index for assessing relative growth rate and age of various body parts. Dried eye lens weight is a particularly good indicator of relative age in the springhare because of its considerable change in size during the life of this nocturnal mammal. Dried eye lens weight increased by a factor of eight, from 80mg at birth to more than 600mg in the "oldest" individuals. In comparison, the dried eye lens weight is only 71mg in the 7.2kg howler monkey Alouatta caraya, (Malinow & Corcoran 1966), 380mg in the 3.7kg mountain hare Lepus timi- dus (Flux 1970), and llOOmg in the full grown zebra Eauus burcheZZi stal- lion (Smuts 1974). SECTION ONE BURROW STRUCTURE AND FOSSORIAL ECOLOGY OF THE SPRINGHARE INTRODUCTION This section presents data on the structure of the burrow and the fossorial ecology of the springhare. MATERIALS AND METHODS Three typical well-established springhare burrow systems were ex- cavated by spade and by hand. Tunnel systems were mapped and descrip- tive notes made. Burrow System One was located on the Eastern Study Area in the vicinity of the Gaborone sewage treatment ponds. Burrow Systems Two and Three were situated on the Kalahari Study Area near the Game Scout Camp. Percentage estimates were made of the grass species composition within 3m of the burrow entrance and within the area between 3m and 20m from the burrow entrance. These estimates were obtained for thirty-six different burrow systems in the northeastern sector of the Kutswe Game Reserve from March through June 1972, the latter half of the growing (wet) season. Grass species composition on the area further than 20m from the burrows was determined using the Riney (1963) line-point transect o 14 15 RESULTS AND DISCUSSION External Morphology Springhares combine morphological features necessary for living in a nocturnal terrestrial environment with those required for the construc- tion of burrows and life underground. External features associated with terrestrial activities include elongated and powerful hind feet, long tail and ears, and large eyes. These physical characteristics are usually reduced in highly fossorial mammals (Ellerman 1956). Modifications for subterranean life include slightly valvular nostrils; ears which fold lengthwise along the mid-line to prevent entrance of soil (Pocock 1922), and short, strong, long-clawed, front feet for digging. Many of these external features are also evident in the rodent families Heteromyidae and Dipodidae whose members, although considerably smaller than the spring- hare, occupy a similar ecological niche. Location of Burrows Burrows were situated in loose to hard-packed sandy soils. Clay, gravel and poorly drained soils were not used and evidently did not pro- vide suitable burrowing sites. Springhares occurred in highest numbers on flat Open terrain where burrowing sites were associated with abun- dant short-grass food resources. Springhares made little use of forage located more than 400m from the nearest burrowing site (Smithers 1971; Butynski 1975). Digging Behavior One free-living springhare was observed with binoculars at night under a full moon. This individual entered the burrow head first, re- appeared just inside the burrow two or three minutes later, looked out 16 for a few seconds and then leaped to the top of the dirt pile at the burrow entrance. It then appeared to view the surrounding area for ap- proximately 30 seconds. Turning around, it removed the accumulating soil from within the burrow entrance by throwing it underneath the body with its front feet. The soil was scattered by shifting the body weight to the front feet and rapidly kicking the hind feet simultaneously once or twice. This procedure was repeated continuously during the one-hour period prior to daybreak. From this observation and those on captive springhares, and from the structure of the burrow and the springhare's external morphology, it is believed that the following general burrowing procedure prevails. The front claws loosen soil from the burrow wall while the teeth out through roots. The front feet toss the soil beneath the body and the hind feet kick it further back. When the pile of loosened soil is large enough, the springhare turns around, and with its chin, chest and front feet held up against the pile, it pushes the soil to the entrance with thrusts of the hind feet. The springhare then leaps from the burrow, looks around and scatters the soil as already described. Description of the Burrow System For the three springhare burrow systems excavated (Figures 5, 6 & 7), the following values were obtained: mean depth - 78cm, mean length - 42.1m, mean number of entrances - 9.3, and maximum depth - 122cm (Table 1). Tunnels varied from 12-25cm in height, and from 10-23cm in width; they were generally 3-6cm.higher than wide and their distance from the surface varied little throughout their length. Burton & Burton (1970), Matthews (1971), and Kingdon (1974) referred to chambers, side-pockets, and blind tunnels within springhare burrows. Roberts (1923, 1951) made l7 moaouwo some .moHo: cmoao ucomouoou moaouwo ofiaom mam moHo: oases uaowouoou .o>oom Eoum comm me one Eoumzm 3ouuom mumnwafiunm mo mafiamuo oflumawaom .m muowwm 18 EN. 0. h p .m ouswwm b h p b h 0’2 C» l9 mmHouwo ammo .onoz :mmHo uaomoueou mmaouwo ofiaom one moao: memos unmmmuamu .o>oom Eouw comm mm 039 Emumxm Bowman oumnwcfiunm mo wcwamuo oHumEmnom .e whowfim 20 F~L .c ohswwm 0’2 21 moaoufio ammo .moHo; cacao ucomouamu mmHouHu oHHom one mmao; canoe uaommuaou .o>oom Boom Comm mo saucy Eoumzm Souusm mumcwcfiuam mo mcw3muo Ufiumsmnom .n ouawfim 22 .m ouzmwh a» D D D b h NZ 23 somemame N o ¢.mm an Hmuuamo m “nonmamx q n o.mq ow Hmuucou N mco3muom g m n.c< an cumummm a A15 A58 mmaon sumac moao: oases Suwaoa noose coaumooa noneas mo umoaoz Mo poneaz HouOH use: Hmaowwom Bonusm .wcowuwawwmo one mawmuoo How uxmu mom .msouuoo mumswcwuem Hoowohu Donna so some .H oHan 24 no mention of these formations and he specifically notes that nests were not found. None of these formations was found in the present study. Food and nesting materials were not located in the burrows; the only items in the burrows were fecal pellets. Burrow entrances were of two types, "mound" holes and "clean" holes (Roberts 1951; Kingdon 1974). Mound holes had a crescent-shaped mound of soil at their entrance. This mound consisted of soil removed from the burrow and averaged 2.5m across, 1.5m in width, and 0.2m in height. Tun- nels entered the ground at an angle of approximately 40 degrees, and maintained this slope for 1.5m, or until they reached a depth of 70cm to 100cm. At this depth the tunnel became horizontal. Clean holes lacked the earth mound, and were therefore less conspicuous than mound holes. Unlike mound holes, clean holes were excavated from the inside and dropped nearly straight down to join the main tunnel. Both types of holes were used regularly by springhares for both entering and exiting, although Roberts (1923) stated that clean holes were most often used. In the three burrows excavated, mound holes outenumbered clean holes three to one. The two types of holes may be important in predator avoidance and in de- termining the amount of ventilation within the burrow system (Vogel, Ellington & Kilgore 1973; Vogel 1978). Short, temporary, earthen plugs were often found just inside mound holes. These plugs, formed from inside the burrow, reduced ventilation within the burrows, and probably discouraged predators from entering. Much longer, permanent, earthen plugs were found in each of the three burrows excavated. These sometimes filled entire tunnel-branches and varied in length from 0.5m to over 3m. Similar plugs have been reported in prairie dog Cynomys Zudbvicianus burrows, where they are said to 25 function in alteration of burrow design (Wilcombe 1954), removal of fecal and other undesirable materials (Smith 1958), and predator avoid- ance (Henderson, Springher & Adrian 1969). Plugs in springhare burrows probably represented the accumulation of soil removed during excavation of new tunnels. This was also concluded to be their origin in woodchuck Marmota monax (Grizzell 1955), and in pocket gopher Thomomys bottae (Crouch 1933; Howard & Childs 1959) and Geomys bursarius (Kennerly 1964) burrows. The overall pattern of springhare burrow systems was much more circular than those described for most other rodents. The majority (24 of 28) of entrances in the three burrows excavated were located on the periphery of the systems, while most tunnels led toward the center of the system (Figures 5 & 6). .Although many burrow systems were examined, only one was found with only two entrances. It is thought that this burrow, with its one mound hole and one clean hole, represented an initial stage of what eventually mdght become a more complex system. The paucity of newly-initiated burrows probably indicates that most burrow systems were utilized by a succession of springhares over many years. It appears that tunnels were added to the simple two-hole burrow until a size was approached beyond which springhares began either to neglect or to actively plug older sec- tions. Apparently, new tunnels were added and older ones abandoned as long as the burrow was occupied. If this reasoning is correct, Burrow System One (Figure 5), with its many short passageways connecting major tunnels, was probably older than Burrow System Three (Figure 7) with its simpler pattern. 26 Time of Excavation Although springhares burrowed throughout the year, this activity increased considerably during the period of highest rainfall, usually from December through March. Miller (1948) concluded that seasonal bur- rowing of T. bottae was correlated with rainfall, and thus soil moisture, since moist soil is most easily excavated. Certain soil types, notably the red clay-sands of eastern Botswana, were much easier to dig when moist. The increased burrowing activity of springhares during the rainy season may also indicate that nutritional requirements were more easily met at this time. Number of Springhares per Burrow System Springhares often formed feeding groups of several individuals (Butynski 1975). Each springhare moved to a separate burrow system when these groups were disturbed. Evidently, only one springhare, or at most a mother with its one young, was associated with each burrow. This ob- servation agrees with those of Shortridge (1934), Matthews (1971), Smithers (1971) and Kingdon (1974). Burrows were not closely associated with one another in areas with ample burrowing sites. However, limited burrowing sites in an other- wise optimal springhare habitat resulted in the excavation of many bur- rows in a relatively small area. Some burrows probably became intercon- nected under such conditions. Functions of the Burrow Springhares did not drink water but apparently met their moisture requirements from rain and dew drops on vegetation, from free water in food eaten and from oxidation of hydrogen in food (Schmidt-Nielsen 1964; Bartholomew 1972). The springhare's habit of limiting all above-ground 27 activity until after dark, when temperature was lowest and humidity was highest, aided in the conservation of energy and body water. Several workers (Turnage 1939; Vorhies 1945; Geiger 1950; Pruitt 1959; Hayward 1961; Kennerly 1964; Ruffer 1965; McNab 1966; Kay & Whitford 1978) have shown that, in general, burrows provide a microenvironment of rather moderate, stable temperature and high humidity. Thus, while in the bur- row, it is unnecessary for small mammals to engage in active heat regu- lation (Vorhies 1945; Schmidt-Nielsen & Schmidt-Nielson 1950; Schmidt— Nielson 1964; Bartholomew 1972). Springhare burrows were dug in sandy soils. Since these soils are relatively porous they provide good insulation (Geiger 1950). Burrow entrances and much of the ground in which burrows were excavated were of— ten shaded by the only large tree or clump of bushes in an otherwise open area. This plant cover contributed to the insulation of the burrow (Geiger 1950). The presence of many 90-degree angles within the burrow system, the differential exposure of entrances to wind currents, and the difference in size and shape of the two types of entrances are features which increased the air (oxygen) flow through the burrow (Vogel, Elling— ton & Kilgore 1973, Vogel 1978). Springhares moved to their burrows when disturbed. Predator avoid- ance was the most obvious and certainly one of the most important func- tions of the burrow. Springhares are of a size (0.3 - 3.5kg) which at- tracts a large number of predator species (Section Three) (Table 2). Springhares were born in the burrow at a body weight of about 2503. Here they remained for an estimated seven weeks by which time they had attained a body weight of approximately 1.3kg (Section Four). Predators capable of removing springhares from.their burrows include man Hamo sapiens, honey badger MeZZivora capensis, monitor lizard varanus Table 2. 28 Cited and probable predators on the springhare in Botswana. Scientific name Common name Source *Acinony: jubatus Schreber Eitis arietans Merrem ‘Bubo Zacteus Temminck Canis adustus Sundevall *Canis familiaris L. *Canis mesomelas Thomas Crocuta crocuta Brxleben Dendroaspis poZyZepis Gunther *FeZis caracai Roberts ‘Felis Zibyca Thomas *Felis seruaZ Schreber Genetta spp . *Homo sapiens L. *Hyaena brunnea Thunberg Lycaon pictus Temminck .‘IeZZivom capensis Schreber Manges pulverulentus Roberts Panthera Zeo L. ‘Panthera pandas L. Python sebae Cmelin Polemoetus beZZicoaus Daudin veranus eranthamaticus Daudin Vhlpss chama Smith cheetah puff adder giant eagle owl sidestriped jackal domestic dog black-backed jackal spotted hyaena black mamba caracal African wild cat serval genet man brown hyaena wild dog honey badger gray mongoose lion leopard python martial eagle monitor lizard cape fox FitzSimons (1920). Labuscagne (pers. comm.) Bushmen (pers. comm.) FitzSimons (1920), Bush- men (pers. comm.) probable predator Roberts (1923, 1951), this study Grafton (1965). Smithers (1971). this study Smithers (1971) Bushmen (pers. comm.) Smithers (1971) Smithers (1971) FitzSimons (1920) FitzSimons (1920) Kingdon (1974) Roberts (1923, 1951), Smithers (1971), Butynski (1973), Kingdon (1974) G. Mills (unpubl. manuscript) Estes and Goddard (1967) probable predator FitzSimons (1920) Eloff (1973) Mitchell et al. (1965), Grobler and Wilson (1972) Bushman (pers. comm.) Bushmen (pers. comm.) Business (pers . coals .) Bothna (1966, 1971) *Probably a primary predator species of springhares. 29 eranthematicus, and several species each of mongooses and snakes. Bushmen hunted springhares during all months, but particularly during the wet season as it was at this time that it was easiest to detect whether or not burrows were occupied. (Butynski 1973). Roberts (1951) was informed by Thomas Ayres that he often secured springhares by "...waiting at the exit of these (clean) holes at dusk and, just at the fall of darkness, when they would spring out and be sil- houetted against the sky above the level of the thorn trees for a mo- ment, he would shoot them." This leaping behavior was not observed during the present study but, since springhares are capable of 1m vertical jumps, it is possible that they leap from the bottom of the burrow out through the clean holes. Springhares were observed to bolt suddenly and rapidly from inside the mound holes to a point 2-3m in front of the entrance. This rapid movement may aid in predator avoidance. As mentioned above, burrows were often located near the largest tree or the only clump of bushes within the springhare's home range. It is suggested that these served not only as shelter and concealment, but also as easily recognized reference points toward which springhares could move when disturbed or disoriented. Of the larger burrows found in Botswana, those of springhares are the most common. Their size makes them suitable refuges for many other animals, a preliminary list of which is presented by Smithers (1971). Effect of Burrows on Vegetation Burrowing by rodents can affect both soil and vegetation (Grinnell 1923; Formosov 1928; Greene & Murphy 1932; Greene & Reynard 1932; Ellison 1946; Wallihan 1947; Merriam.& Merriam 1965). Rodents influence vegeta- tion around burrows through exposure of fresh soils, preferential 3O utilization of certain grasses, and deposition of fecal pellets. In the bush savannah of the Kalahari the grass vegetation adjacent to spring- hare burrows differed markedly from that of the surrounding area. Eragrostis Zehmanniana and Eragrostis atherstoni are extremely hardy grasses which play pioneer and subclimax roles in the Central Kalahari Bush Savannah. These grasses were only slightly more prevalent within 3m of springhare burrows than in the savannah 20m or more away (Table 3). Grasses of the genus Urochloa were the principal colonizers of the 3m zone of newly exposed ground at burrow entrances. It is interesting to note that the green seeds of Urochloa spp. were probably also the most preferred springhare foods during the wet season. Urochloa spp., Tragus berteronianus, Enneapogon cenchroides and Aristida hordeacea showed the greatest affinity for the disturbed conditions associated with springhare burrow openings. Schmidtia pappophoroides and Stipagrostis uniplumis, which formed 65% of the grass cover in the bush savannah away from bur- rows, comprised less than 15% of the grass cover in the 3m and 20m zones adjacent to burrows (Table 3). Alterations in grass species composition due to springhare burrowing were also obvious in the open grasslands of the Makgadigadi Salt Pans in north-central Botswana. 31 Table 3. Percentage composition of grasses occurring in each of three zones around 36 springhare burrow systems in the Central Kalahari Bush Savannah. Percent composition* Crass species 3m radius 3-20m radius more than 20m ______"‘___----‘__ of bugggw of burrow____£Egmubu££gw_____ Anthephora pubescens Nees - - 1 Aristida congesta Roem. & Schult. l l 3 'Aristida hordeacea Kunth 4 5 - Chloris virgata Swartz 1 1 - cenchrus ciZiaris L. - 1 1 Digitaria spp. 1 1 1 Enneapogon cenchroides Licht. 15 24 2 Eragrostis Zehmanniana Nees & Eragrostis atherstoni Stapf 30 34 23 Pogonarthria squarrosa Licht. - - l Schmidtia pappophoroides Steudel 6 2 49 Stipagrostis uniplumis Licht. 8 7 l6 Tragus berteronianus Schultz. 14 18 l Triraphis fleckii Back. 1 l 1 Urochloa spp. 18 5 1 *Grasses accounting for less than one percent of the composition are not included. SECTION TWO PELAGE AND MOLT IN THE SPRINGHARE INTRODUCTION Molt in tropical and equatorial wild mammals is not well—documented. In a review of the literature only three papers were found which dealt with molt in African mammals (Meester 1958; Vijoen 1975; Baxter 1977)- Ling (1970), in his comprehensive review of pelage and molting in wild mammals, indicated a need for additional information in this area. Pelage of the springhare and the process, timing and duration of its molt were studied. MATERIALS AND METHODS In this section, "rainfall" is the mean total monthly rainfall based on 30 years of data (1939-1969) for Gaborone (Botwsana Meteoro- logical Services). "Temperature" is the mean daily air temperature for each month as derived from nine years of data (1958-1967) for Gaborone (Siderious 1972). "Forage protein" is the percentage protein in spring- hare stomach contents collected in this study during each month from August 1971 through August 1973 (n . 542). "Day length" is taken from Smithsonian Meteorological Tables (List 1966) and represents the number of daylight hours at mid-month. Mean monthly sample size from September 1972 through July 1973, for both areas combined, was 29.5 i;0.25 springhares. In addition, two spring- hares were collected in August 1973. Further, observations were made on the molt pattern of six captive springhares and from examination of 32 33 springhare study skins in the National Museums of Rhodesia; 308 of which were collected from all parts of Botswana and 63 from Rhodesia. Felts and molts were classified as either juvenile or adult, the percentage of new pelage was estimated, sketches were made of the molt A pattern, and photographs were taken of many springhares in molt. An accurate ageing criterion was not available for springhares. Therefore, body weight was used to indicate relative age. A body weight of 2.6kg was used to separate juveniles from adults. Body weights are related to eye lens weights and other body measurements in Section Six. Preliminary analysis of the data indicated that neither locality nor sex influenced the pattern of molt, age at first molt, or timing of the molt. All of the springhares examined, therefore, were considered to be from one population, and for some of the analyses the data have been combined. Hair type, pelage stage, and molt pattern, were classified according to Danforth (1925), Negus (1958), and Stodart (1965), respectively. RESULTS PelagEQStages The gestation period of the springhare is approximately 77 days (Rosenthal & Meritt 1973; Velte, in press). Fur starts to appear at about 17 days before birth (Section Four). Thereafter the pelage deve- lops rapidly on the foetus. Dense brown fur first appears on top of the head and then on the tail, nape, hips, and rump. At birth, the entire dorsal portion of the body is covered with a dense brown fur which, ex- cept on the ears, tail, and outer parts of the legs, is overlain by longer, black guard hairs. The belly, neck, genitalia, insides of the legs and soles of the feet are nearly naked. Velte (pers. comm.) remarked that the 34 underparts do not possess a good fur covering until at least three weeks after birth. Springhares were not observed during the period one week after birth to the time they first emerge from the burrow (body weight > 1.3kg). Thus, it is not known whether the pelage classified here as juvenile re- presents the first fur covering or is preceded by one or more molts. In the juvenile pelage, the upper parts of the body, the lower half of the ears, and the first 20cm of the tail are brown. The underfur on the back is relatively thick and 25-33mm in length. The proximal half of these hairs is a dull cream color, and the distal half is glossy brown. A sparse covering of 35mmrlong black guard hairs overlays the underfur of the back. The brown fur on the tail is coarser and duller than that on the body, is 50-60mm in length, and lacks cream color on its proximal half. Fur on the last 20cm of the tail, upper half of the ears, and soles of the hind feet is black, as are the vibrissae. The only other black fur occurs as a large, clearly defined area on the underside of the base of the tail. Underparts and insides of the legs vary in color, de- pending upon the subspecies, from white to light orange. Belly fur is 20-30mm in length, fine in texture and sparse. Guard hairs are lacking over those parts of the springhare covered with white fur and on the tail. Adult pelage is similar to juvenile pelage but coarser and darker, the underfur on the back is gray at its base rather than cream-colored, and the black fur at the base of the tail and on the bottoms of the hind feet changes to light gray or cream. Molt Pattern A "molt line" occurs where shedding pelage gives way to new pelage. Observation on movement of the molt line from the beginning to the end 35 .mawmuoo pow uxou mom .ommaoa Bo: ucomopoou momma esteem .opmswcwmem one cw commune “HOE Hmmuoo ecu mo cofimmouwoum .w ohswwm g 3 36 of the molt provides a "molt pattern". The molt line in springhares is distinct only where brown fur is overlain with guard hairs. It is, therefore, not possible, using the present method, to determine the molt pattern, or even the timing of molt on parts of the body where guard hairs are lacking. The juvenile molt removes the juvenile pelage and brings in the first adult pelage. All subsequent molts are termed adult molts. No differences were found in the patterns of molt between either juvenile and adult, or male and female springhares. Springhares have a caudad molt pattern. Pelage replacement begins on the face, muzzle and base of the anterior side of the ears (Figure 8). The molt line progresses in a "U-shape" over the tor) of the head, nape, and front half of the back. The U-shaped molt line is usually evident until completion of the molt at the base of the tail, but may become straight, jagged, or indistinct. Age at Molt In a sample of 183 springhares, all of which had at least some ju- venile pelage, the lightest animals in molt weighed 1.7kg. None of the 16 individuals weighing less than 1.7kg had begun the juvenile molt. Thirteen percent of the springhares weighing between 1.7kg and 2.1kg, and nearly 90% of those weighing between 2.2kg and 2.9kg were in juvenile molt. Most springhares completed the juvenile molt before attaining a weight of 2.5kg, although some were nearly 3.0kg. This molt commenced after springhares started to feed outside their burrows (body weight > 1.3kg) and before most reached sexual maturity (body weight 5 2.6kg). Springhares occasionally entered into the first adult molt at a weight of 2.6kg, but most weighed between 2.7kg and 2.9kg. weight and 37 age of a springhare at first molt apparently depended largely on the time of year at which it was born. Time Required to Undertake Molt There was no significant difference between the percentages of ju- venile males (55% of 49) and juvenile females (73% of 45) in molt (x2 - 3.40, d.f. - 1, P > 0.07), or between adult males (22% of 122) and adult females (1574 of 110) in molt (x2 - 2.22, d.f. - 1, p > 0.14). These data suggest that there is no sex difference in the amount of time required to undergo molt. A highly significant difference existed, how- ever, between percentages of juveniles (64% of 94) and adults (19% of 232) in molt (X2 I 63.49, d.f. I 1, P ‘<0.0001). It is not known why, in the collection of the National Museums of Rhodesia, the percentage of juvenile specimens in molt was considerably smaller (26% of 122) than in the sam- ple obtained during the present study (64%). This was true even though the percentage of adults in molt in the two collections was similar (15% of 257 vs 19%). Only one of 26 non-pregnant females was in molt whereas 16 of 84 pregnant females were in molt. This difference is nearly significant (x2 - 3.52, d.f. - 1, p > 0.06). Time required to molt varied considerably among individuals and with the stage of molt. A juvenile female captured at a weight of 1.2kg began the juvenile molt 10 weeks later at a weight of 1.7kg and com- pleted the molt in 30 days at a weight of 2.0kg. Three adult females, each with 80% of the adult molt completed, required an additional four, seven, and ten weeks, respectively, to complete the final 20% of the molt. Another adult female required six weeks to undergo the complete adult molt. The effect of captivity on the molting process is unknown. 38 In the present study, so far as is known, springhares were col- lected randomly. Whether or not a springhare was collected was apparently independent of its stage of molt. The relative rate of molt line move- ment from head towards the tail was determined by comparing the number of springhares occurring within each category of fur replacement (per- centage new pelage). If the rate of molt line movement was the same during all phases of molt one would expect each phase to be equally re- presented in the sample. In 165 molting springhares the rate of pelage replacement was fairly constant except for the last 4cm or so on the rump. Since 53 (32%) of the molting springhares exhibited molt lines in this area, the molt over the last 10% of the body apparently progressed faur times more slowly than over the anterior 90% of the body. RelationshipiBetween the Time of Molt and Environmental Factors Monthly percentages of springhares in juvenile and adult molt Y were transformed by loge (Y + 1) and their degree of assocation with four environmental parameters tested by least square linear regression. The juvenile molt occurred at all times of year with evidence of an increased molt activity from January through April (Table 4) when most (SO-70%) juveniles were in molt. The monthly percentages of springhares undergoing juvenile molt showed significant positive correlations with rainfall (r I 0.619, d.f. I 10, P <0.025), air temperature (r- 0.600, d.f. I 10, P <0.025) , and forage protein (1' I 0.582, d.f. I 10, P < 0.025), but not with day length (r I 0.472, d.f. I 10, P > 0.10). During 1972-73, the annual adult molt was confined to the period between November and May, inclusive. Peak months for adult molt were December and January when more than 40% of those springhares in adult pelage were molting. Study skins in the National Museums of Rhodesia 39 showed that during some years a proportion of the Botswana population underwent adult molt in June, September, and October (Table 4). No springhares were found in adult molt in July or August. Monthly percentages of adult springhares in molt yielded highly significant positive association with rainfall, air temperature, and forage protein (Figure 9). Not only did springhares in adult molt ex- hibit higher correlation coefficients and levels of significance with environmental variables than did springhares in juvenile molt, they also showed strong association with day length (Figure 9). DISCUSSION Occurrence of the juvenile molt in springhares was correlated with rainfall, air temperature, and forage protein. It was also associated with age and body size, a relationship also observed in muskrats 0ndatra zibethica (Errington 1939), meadow voles Microtus pennsylvanicus (Coin 1943), California voles Microtus califbrnicus (Ecke & Kinney 1956), brown rats Rattus norvegicus (Mohn 1958), and hispid cotton rats Sigmodon hispidus (Chipman 1965). Although physical condition (Section Seven) and reproductive effort (Section Three) in springhares appeared to be unrelated to seasonal en- vironmental changes, this was not the case for the adult molt. The highly significant correlations of molt with rainfall, air temperature, forage protein, and day length, suggest that timing of this molt has evolved so as to circumvent that period of the year when temperature and rainfall are lowest, and nutrients scarcest. The replacement of adult fur occurs at a time when environmental conditions are most favorable (Section Seven) as has been cited for a number of mammalian species in many environments (Ling 1970, 1972). 4O _.- ~.m_ c.n~ w.- o.~_ ¢.—_ w.c— o.o~ m.o_ n.__ N.N~ c.n_ c.m_ any someoa hon o.c_ m.o_ ~.- _.m_ m.__ ~.o_ m.__ n.~_ ~.o~ q.n— ~.o~ n.c— n.m~ any cumuoum m.m~ N.o~ n.q~ o.m~ o.c~ m.n~ o.~_ o.~_ o.m~ m.m~ o.m~ o.n~ n.n~ Aoov ousuouoeeua ~.o~m m.wm n._o —._q m.—— —.v m.m o.m e.o_ c.~c a.a~ n.0m n.0m Aaav udmunwmm q.m_ ow nN - o o o N m m __ ~N Ne uuos cw madame N on - m m N o 0 ~ _ N c m— ON uqoa cu magnum .oz mmc NN mm _c _m mu we cc mm _c um um we mounts Hooch m._e we no no we a we mu an _N mm mm mm mass =« nouwno>sn N .m o a o q _ m c 0 cu u - 0_ uaoa :« mouwco>sn .oz m—m m. oN q~ m Nd a— mm Nm o— N. Na m~ mounmo>na umuoa means no so: >oz moo mom wz< new one >6: ua< am: mom can Sumo: Home? .nuwcofi xmm :u:06|o«a one .cuoDOHQ unseen some .oununuoaeou nus some .Humunfimu Hausa new mo=Hm> hazucoe one .munoeosm one messages nu memos u~soo can o~u=o>sn cu mononwcnuae mo nodusouuumwo masons: .q muons Figure 9. Log, (7. in molt + I I 41 rog,(v+ n - 0.033 x+0.sso (r-O.883,df-IO. P< 0.005) oh.- 1 1 1 1 _1 1 0 I5 30 45 60 ES 90 KB Rainfall (mm) b roq.(v+n-0.240x-2.soo (r-O.935.df'IO,P<0.005) o l l l l J I2 I4 I6 l8 20 22 24 26 Temperature (C') 4- 3 r- 2 _ loo, Hakeem-3.4” tr-0.7sr.dr-I0.P<0005) 0.. I 1 1 1 1 1 J I00 ”.5 I30 I45 l6.0 I75 l9.0 20.5 Protein 00 4- 3.- 2.. _, ' Iog.(Y+I)-I.OOOX-I0999 (:s0.9|3.¢9-r0.p<0.005) o . l l l A l l l l l0.5 I LG I |.5 I20 I25 I10 I35 I40 Day - length I hows) Relationship between the percentages of springhares in adult molt Y and (a) total rainfall, (b) mean air temperature, (c) mean during each of twelve consecutive months. Sample sizes as in Table 4. See text for details. forage protein, and (d) day length at mid—month 42 Fat deposition occurred throughout gestation and fat reserves were drained during lactation (Section Seven). Clearly, lactation was the most stressful phase of the springhare reproductive cycle. The lowest occurrence of molt was in non-pregnant adult females, 78% of which were lactating. This strongly indicates that lactation hinders the molt process. Lactation also has been interpreted as interrupting, ar- resting or preventing the completion of malt in a number of rodents in- cluding squirrels Sciurus spp. and Tumias spp. (Allen 1894), spiny pocket mice Heteromys spp. (Goldman 1911), prairie dogs Cynomys spp. (Hollister 1916), deer mice Peromyscus maniculatus (Collins 1923), pocket gophers Thomomys umbrinus (Morejohn & Howard 1956), R. norvegicus (Mohn 1958), S. hispidus (Chipman 1965), and pocket mice Perognathua parvus (Speth, Pritchett, & Jorgensen 1968; Speth 1969). The adult molt in springhares was synchronous in that it occurred predominantly during the period November through February. However, considerable individual variation in the inception. progression, and duration of molt, particularly among adult females, was also noticeable. This variability does not necessarily indicate a reduced sensitivity to environmental stimuli at the individual level. In fact, much the opposite is more likely the case. Molt in springhares appears to be a chronologi- cally flexible phenomenon which is delayed or retarded during times of stress, and initiated or speeded-up when conditions are most favorable. Ling (1970) mentions several cases in which the related factors of physi- cal condition and reproductive state are known to act alone or in combina- tion to block or promote molt in mammals. After reviewing the literature, Ling (1970) concluded that molt in mammals is "...an inherent character- istic coordinated with respect to season by photoperiod but modified 43 locally by such indirect factors as temperature and behavior and, more directly, by nutrition." The present study of a tropical rodent found nothing to contradict these conclusions. SECTION THREE REPRODUCTIVE ECOLOGY OF THE SPRINGHARE INTRODUCTION Data concerning the reproductive ecology of the springhare are very limited. Based upon zoo records, the gestation length has been estimated at 80—82 days (Rosenthal & Meritt 1973) and 72-82 days (Velte, in press). Smith (1965) made general observations on the reproductive tracts of 27 springhares from Rhodesia. Coe (1969), working in Kenya, provided a detailed description of the reproductive tracts of male and female springhares. Mossman (1957) examined the placenta 0f the spring- hare, Mossman and Fischer (1969) described the preplacenta, and Fischer and Mossman (1969) considered the taxonomic significance of the foetal membranes. A detailed account of the external morphology of a single foetus was given by Jones (1941). Birth, and initial neonate-mother behavior, have been witnessed in captivity by Hediger (1950), Coe (1967), Rosenthal and Meritt (1973), and Velte (in press). Smithers (1971), working in Botswana, presented data on reproduction in springhares, some of which will be compared with the findings of the present study. This section is concerned with the reproductive ecology and repro- ductive strategy of the springhare. Detailed descriptions and interpre- tations of gonadal development and activity of male springhares (Section Five), and the growth and development of foetuses (Section Four) are pre- sented elsewhere. 44 45 METHODS Springhares were weighed to the nearest gram and conventional museum measurements were taken to the nearest millimeter. Testes, epididymides, ovaries, and vaginae were measured to the nearest milli- meter. Testes, seminal vesicles, and foetuses were weighed to the nearest decigram (dg). Notes were made on the sexes of the foetuses and their locations within the reproductive tract. A springhare gestation period of 77 days was used in this paper. This is based on the data of Rosenthal and Meritt (1973) and Velte (in press). RESULTS Juvenile : Adult Ratios and Sexual Maturity Adult female springhares were distinguishable from juveniles on the basis of their much larger reproductive tracts. Using this criter- ion, the juvenile to adult ratio was 29:71 (45 to 109) on the Kalahari Study Area and 26:74 (32 to 90) on the Eastern Study Area. These age ratios were not significantly different (x?< 0.3, d.f. - 1, I’> 0.3). Most female springhares conceived for the first time at an eye lens weight of approximately 325mg and a body weight of about 2.7kg. Using an eye lens weight of 325mg to separate juvenile from adult fe- males the age ratio on the Kalahari Study Area was 26:74 (40 to 114) and that on the Eastern Study Area was 27:73 (33 to 89). The age ratios derived using eye lens weight were not significantly different from those obtained when reproductive tracts were examined (x2‘<0.4, d.f. B 4, P > 0.3). Gross visual examination of the female reproductive 46 tract was used as a standard against which to assess the usefulness of the 325mg dried eye lens weight criterion for separating juvenile from adult female springhares. 0n the basis of a 325mg eye lens weight, the reproductive status of only fifteen (5%) of the females was not assessed "correctly". Since visual assessment of reproductive tracts is itself an imperfect criterion, the "325mg dried eye lens weight" criterion should be suitably accurate for most analyses as a means of distinguishing juve- nile from adult female springhares. Using the presence of spermatozoa in the testes to separate juve- nile from adult males (Section Five), the juvenile to adult ratio for males on the Kalahari Study Area was 31:69 (51 to 114), while that on the Eastern Study Area was 25:75 (30 to 89). There was no significant dif- ference between the age ratios of males collected on the two study areas (x2 < 1.0, d.f. - 1, p > 0.3). Significant differences were not observed between the age ratios of males and those of females within study areas (x2'<0.1, d.f. - 1, P > 0.3). The age ratios for males and females combined were not signi- ficantly different between study areas (x2 - 1.29, d.f. - l, P > 0.2). The overall age ratio was 28:72 (77 to 199) for females and 29:71 (81 to 203) for males. The difference between these ratios was not significant (X2 - 0.07, d.f. - 1, P > 0.3). The overall juvenile to adult ratio, regardless of sex or study area, was 28:72 (158 to 402). Ovaries, vaginae, and uteri did not cease rapid growth until an eye lens weight of approximately 350mg and a body weight of about 2.8kg were achieved. Rapid growth of the testis, epididymides, and bacula did not cease until males attained a body weight of about 2.9kg and an eye lens weight of approximately 425mg. The penis became free to extend out of its sheath at an eye lens weight of approximately 275mg and a body 47 weight of about 2.3kg. All male springhares with a dried eye lens weight greater than 344mg showed spermatogenesis (Section Five). Sex Ratios Among foetal springhares large enough for sex determination the (primary) ratio of males to females was 51:49 (45 to 44). On the Kalahari Study Area the (secondary) sex ratio, for juveniles and adults combined, was 165 (52%) males to 154 (48%) females. On the Eastern Study Area the secondary sex ratio was 119 (49%) males to 122 (51%) females. The overall male to female ratio for juveniles was 51:49 (81 to 77) while that for adults was 50:50 (203 to 199). Overall the collection of juvenile and adult springhares consisted of 51% males and 49% females. No significant difference from parity was found between primary and se- condary, or juvenile and adult sex ratios, or between the sex ratios of springhares from the two study areas (x2 < 0.315, d.f. - l, I’> 0.3). Vaginal Plugs A vaginal plug was found in each of two female springhares. One of the plugs weighed 8.03. Both of the females showed newly implanted blastocysts. Pregnancy,Rates On the Kalahari Study Area, 80% (87 of 109) of adult female spring- hares were pregnant, while 722 (65 of 90) were pregnant on the Eastern Study Area. The difference between pregnancy rates on the two study areas was not significant (x2 - 1.28, d.f. - 1,? > 0.25). Overall 76% (152 of 199) of adult females, and 55% (152 of 276) of all females, were pregnant. Smithers (1971) found that 49% (111 of 227) of all female springhares he collected in Botswana were pregnant. The percentage of all females 48 which were pregnant did not differ between the two studies (x2 = 1.91, d.f. - l, P > 0.1). The length of the mean non-pregnant period can be estimated by solving for X’in the following proportion: Numbergpregnant = Gestation period (days) Number of adult females not pregnant X 122. g 77 d3 5 therefore X = 24 da 3 47 7 y This gives a mean interval between conceptions of 101 days (77 days + 24 days). Since springhares breed year round (see below), the average adult female can be expected to undertake approximately 3.6 pregnancies per year. Litter Size and Implantation Sites Springhares are typically monotocous. In the present study one set of twins was found in 152 pregnancies. Smithers (unpublished data) found one set of twins in 104 pregnancies, and Van der Horst (1935) en- countered one case of twinning in a sample of unstated size. Cable (quoted in FitsSimons 1920) failed to find twins in a sample of 500 spe- cimens of all ages and sexes. Twinning thus appears to occur in less than 1% of the pregnancies. Seventy-three foetuses were located in the right uterine horn, and 80 in the left. This difference is not significant (x2 - 0.16, d.f. = 1, P > 0.3). Smithers (1971) obtained similar results with 40 implan- tations in the right uterine horn and 42 in the left. The sets of twins in the present study occurred in the same uterine horn (left), as did the set witnessed by Van der Horst (1935). However, members of the set found by Smithers were implanted in separate uterine horns. 49 Foetal Mortality Examination of 153 foetuses indicated that a prenatal death ob- viously occurred before the death of the mother in four cases. Two of these deaths involved the set of twins mentioned above. The smallest foetus found necrotic weighed less than 0.5g while the largest weighed 5.4g. Lactation and Weaning Lactating springhares were found during all months of the year. Nineteen (79%) of 24 non-pregnant adult female springhares were lactating. Only 4% (5 of 130) of adult females were neither pregnant nor lactating. This latter group probably included some individuals whose pregnancy had been terminated early, or whose unweaned young had died. Overall, 60 (46%) of 130 adult females were lactating and 41 (32%) were concurrently pregnant and lactating. Of the 130 adult females checked for lacta- tion an unknown proportion was primiparous and thus could not possibly be lactating while pregnant. That 46% of the adult females were lac- tating is therefore a minimal figure. As mentioned above, it appears that the interval between conceptions was approximately 101 days. If this was the case, the period of lactation must have been at least 46 days (101 days x 0.46). Lactation ceases with the advancement of pregnancy. Sixty-six percent (55 of 83) of the females with a foetus less than 16g were lac- tating, while only five (38%) of 13 females with a foetus weighing be- tween 16g and 59g were lactating, and none of the 34 females with a foe- tus heavier than 59g were lactating. Springhares were never seen carrying plant materials and no plant parts were found in the burrow systems (Section One). Evidently, the 50 neonate is completely dependent upon the milk of its mother for nutri— tion until it begins to feed above ground. Five (3%) of 158 juveniles collected contained milk in their stomachs. The mean body weight of those five individuals was 1498 :_1723 with range of 12603 to 17843. The low incidence of milk noted in the stomachs of springhares once they begin to feed on grasses suggests a rapid transition from total dependence upon, to complete independence from, the mother's milk. The springhare is precocial at birth (Hediger 1950; Coe 1967: Rosenthal & Meritt 1973; Velte, in press) but, nevertheless, remains within the burrow (Section Four) until its body weight increases from approximately 250g (80mg eye lens weight) to at least 12503 (160mg eye lens weight). Age at first emergence from the burrow is conservatively estimated to be six to seven weeks since the mother lactates for at least this long. Breedin378eason An analysis of variance used to test the interaction between month of collection and those springhare body measurements most likely to in- dicate seasonal changes in reproductive activity (Table 5). There was no statistically significant relationship (I’> 0.06) between time of year (month) and any of the seasonal variables. The formula of Huggett and Widdas (1951), W1’3 - a(t-to) for calculating foetal weight hlfrom foetal age t, was rewritten, t- Ill/3+1: . a O for determing foetal age from foetal weight. Mean birth weight (2523), length of the gestation period fig (77 days), and a constant ‘0 (23 days) Table 5. Summary of an analysis of variance used to test the interaction between the size of the body parts of springhares and month of collection. Dependent Sample variable size n Mean F-value Probability r FEMALES Body weight (3) 274 2778.4 1.758 0.061 0.262 Vagina length (mm) 163 61.1 1.262 0.252 0.290 Right ovary length (mm) 270 8.8 1.038 0.413 0.206 Left ovary length (mm) 272 9.0 1.606 0.094 0.252 XALES Right vas deferens (mm) 148 136.4 0.478 0.914 0.193 Left vas deferens (mm) 147 135.4 0.584 0.839 0.213 Right testis weight (dg) 278 91.0 0.947 0.495 0.194 Left testis weight (d3) 149 91.4 1.065 0.393 0.281 Right testis length (mm) 283 43.3 1.053 0.400 0.202 Left testis length (mm) 153 42.5 0.974 0.473 0.266 Right vesicular gland (d3) 93 48.0 1.163 0.327 0.327 FOETUSES Body weight (d3) 151 523.7 1.545 0.122 0.330 52 (Huggett & Widdas 1951) were used to calculate the springhare specific foetal growth velocity 4 (0.177). The month of conception and approximate age t of each foetus was determined from its weight W’using the equation: 111/3 t: 0.117 + 23. See Section Four for more details. Springhares bred over the entire 24 month collection period. No annual pattern in reproductive effort was discernible (Table 5, Figures 10 & 11). These results not only confirm earlier reports by Coe (1969) in Kenya, and Smithers (1971) in Botswana, that springhares bred year round, but also showed that reproductive effort was unusually constant throughout the year. DISCUSSION Population Regulation The burrow systems of springhares in the Kalahari apparently pro— vided ample protection from the weather. Moderate to heavy rains and un- usually cool temperatures greatly reduced springhare activity (Butynski 1975), but these were short-term phenomena which did not appear to seri- ously affect springhares. External parasites were not common on springhares. Internal para- sites, particularly the stomach nematode, Physaloptera oapensis, were occasionally abundant but no negative correlation between burdens of this nematode and the fertility or physical condition of springhares was found (Section Seven). There was no evidence to suggest that diseases and para- sites contributed significantly to mortality of springhares. Competition for food has often been cited (Lack 1954, 1968; Sadleir 53 §I60 9.140 a '5 I2C) 3 £100 ‘8 '- so 120- 3 b :: lOO' . .C .9 so- ‘5‘ 3 ~ 60- .8 g 40- O 5 20- 0 ll 1 L l l I ll LILIJ A l A I A l A L l l m .5 6°'c 8 40- ‘s’ o 20- 3 0 C .\° °/o pregnant Figure 10. Graphs of those data indicating that springhares bred during all seasons and did not exhibit distinct peaks in reproductive effort. (a) Mean weight of adult male (eye lens weight >350mg) right testis each month with the sample size given at each point. (b) Mean weight of foetuses each month. (c) Percentage of pregnant females in each monthly sample which conceived within 30 days previous to collection. (d) Percentage of adult (enlarged reproductive tracts) females pregnant each month. The sample size given at each point applies also to Figure 10b and can be used to calculate the sample size in Figure 10c. 54 SOOr O E 240 E :6 I80 C '6 120 I- E .. so ,2 0 40r' 35 (n 2 'E 30- O > .2. 25- °\° 20 15 470- C O s E 450 E 430* .E” 3 410- 2 2 390- 0 5' 370- 8 01 350' 2 330- 3'0 1 I I I I I I I LI I I I I I I I I l I I I I I ASONOJFMAMJJASONDJFMAMJJ A 1971 1972 1973 Month Figure 11. Graphs of those data indicating that springhares bred during all seasons and did not exhibit distinct peaks in reproduc- tive effort. (a) Total rainfall for each month in the Kalahari (0—0) and Eastern (O-- -0) Study Areas. (b) Percentage juveniles each month. The sample size is given at each point and can be used to calculate the sample size in Figure 11c. (c) Mean weight of dried eye lens each month. 55 1969) as the most important factor in determining reproductive and survival rates in animals. This is thought to be particularly so for species living in environments with low annual rainfall, pronounced wet and dry seasons, and highly fluctuating food supplies (Delany & Neal 1969; Sadleir 1969). Springhares, however, did not appear to be food limited. Food, in the form of grass leaves, corms and roots, appeared to be abundant during all times of the year. Support for this subjective statement was provided by the good physical condition (Section Seven), and high pregnancy and lactation rates found among springhares during all months. Not only did competition for food ap— pear to be generally absent among springhares but intraspecific compe- tition for other maintenance resources such as burrowing sites also seemed to be low or non-existent. Ricklefs (1973) pointed out that size dimorphism between males and females may serve to separate the sexes ecologically and to reduce intraspecific competition. That secondary sexual dimorphism in the springhare was absent, therefore, lends further support to the hypothesis that competition within the springhare papula- tion was low or absent. Lack (1954, 1970) contends that predation may be more important to the regulation of some herbivorous species than food. At least 21 species of predators feed upon springhares in the Kalahari (Section One). Murphy's (1968) statement that "Larger size, assuming homologous organisms, reduces predation dangers in obvious ways,... " does not seem to apply well to animals in the size category of springhares (2.5 - 3.5k3). These animals are not only vulnerable to small predators such as owls Bubo spp., but are also sought by such large predators as lion Panthera Zea and man Hamo sapiens. 56 Springhares feed in open areas of short grass, often at distances of over 150m from their burrows (Butynski 1975). They are extremely easy to locate and appear to be highly vulnerable and attractive to predators. Upon considering all available data it is concluded that predation is likely the factor most often limiting springhare p0pulations, and thus the primary mover in the evolution of the springhare reproductive strategy. Reproductive Strategy Reproductive effort is the fraction of available time and energy diverted to reproduction (Smith & Fretwell 1974; Demetrius 1975). Fitness of an individual may be measured by the genetic contribution of its de— scendants to future generations (Ricklefs 1973). The reproductive strategy of a species is the result of optimal allocation of energy to maintenance, growth, and reproduction (Demetrius 1975). In general, three patterns of time and energy expenditure by parents on their offspring have come to light (Smith & Fretwell 1974). (i) As the time and energy expended on each offspring is increased, the number of offspring that parents can successfully rear is decreased. (ii) On the other hand, the fitness of the individual offspring increases as the time and energy expended upon it by the parents increases. Thus, in- verse relationships exist between fecundity and parental care, and be- tween fecundity and offspring fitness. The reproductive strategy of the springhare involves high individual offspring fitness at the expense of fecundity. Most of the time and energy allotted the female springhare for reproduction is invested in a single young per pregnancy. This results in low intrauterine, and ap- parently also low neonatal and juvenile mortality. Murphy (1968) claims that, as a predator avoidance strategy, the 57 most obvious way to achieve an increase in body size, in the shortest possible time, is to postpone first reproduction. In the springhare, an additional strategy is witnessed which meets the same end--give birth to a single neonate and funnel much of the time and energy allocated to reproduction into this one individual. The juvenile springhare, when it first emerges from the burrow, has feet and ears 97% and 93% of their adult size, respectively, and appears to be nearly as capable, at least physically, of coping with predators and other environmental hazards as the full grown individual. (iii) As the total time and energy expended on offspring increases, the viability of the parents, and thus their chances of surviving to breed again, is lowered (Gadgil & Bossert 1970; O'Donald 1972; Smith & Fretwell 1974). In this respect, the added exposure (Section Seven) and susceptibility of the female springhare to predators while foraging must be considered. Carrying one foetus (the full-term.weight of which is only 59% that predicted for mammals of this body weight)(Section Four), and providing care and nutrition to only one neonate may be part of a repro- ductive strategy evolved to minimize the female springhare's loss of fitness to predation. The equality of the sex ratio in all age classes is a good indication that female springhares, despite the burden of preg- nancy and of raising young, are no more susceptible to mortality than are males. That springhares do not emerge from the security of the burrow until six or more weeks of age is explainable in terms of predator avoidance. However, the selective advantage of the neonate's well-developed state at birth (Section Four) is less apparent (Hediger 1950). It is suggested that the neonate is mobile within the large complex burrow system, and that this aids in avoidance of burrow-entering predators such as 58 mongooses and snakes. The absence of nests and chambers within the burrow (Section One) supports this hypothesis. SECTION FOUR GROWTH AND DEVELOPMENT OF THE FOETAL SPRINGHARE INTRODUCTION This section describes the growth and development of the foetal springhare and indicates how foetal age can be estimated in the field. MATERIALS AND METHODS Body weight of foetuses was determined to the nearest decigram (d3). All length measurements were made to the nearest millimeter. Forehead-rump: intersection of the coronal and sagittal sutures of the skull to the most posterior part of the rump. Ear length: proximal notch to tip of the ear. Hind foot lenggh: heel to the end of the middle toenail. Overall body lenggh: tip of the nose to the end of the tail, not including the tail hairs. Tail length: dorsal base of the tail to the tip, not including the hairs. Means and standard error of the means were determined for each of the five body measurements in each of 15 categories of body weight for both males and females. Calculations were performed by the Michigan State University CDC 6500 Computer. The computer was also employed to analyze the growth rate of foetal springhares using least squares linear regression. Growth rate values were obtained from the slope constant b in the equation Y = a + b(X) where Y is the length of a body part, a is the intercept-constant, and X 59 60 is body weight in grams. b is the rate of increase of the dependent variable Y (8.9., body length) relative to that of the independent vari- ables X (i.e., body weight). RESULTS AND DISCUSSION Size and State of Development at Birth Mean birth weight of 12 springhares born in captivity (Figure lb) (Hediger 1950; Coe 1967; Rosenthal & Meritt 1973; Velte, in press) was 252 i_193, with a range of 2223 to 3193. Total length at birth ranged from 305mm to 370mm. Of the 153 foetuses collected in the present study, four (2.6%) weighed more than 2633. The heaviest foetus weighed 3003. The smallest neonates born in captivity, excluding an obviously premature 1453 individual described by Coe (1967), appeared to be fully developed, but may have been somewhat premature. This would explain why the heaviest newborn individual weighed 973 (44%) more than the smallest newborn. In addition, it could account in part for the poor survival rate among cap- tive-born springhares (only three of 12 survived for more than a few weeks). Data from this study, together with the work of Hediger (1950), Coe (1967), Rosenthal and Meritt (1973), and Velte (in press), provide the basis for a description of newborn springhares. Neonatal springhares are fully furred and active within a few hours after birth, moving about on all four legs and performing digging and facedwashing movements. At four days of age they are capable of bipedal hopping. The eyes are often open at birth, but may not open fully until two or three days of age. In the newborn springhare, the dried eye lens (80mg) was 11%, the body was 9%, and the right testis (0.13) was less than 1% of the weight of a full-grown animal. Among length measurements the tail was 37%, and 61 the ears and the hind feet were 56% of their eventual full-grown size. Although springhares are precocial at birth they did not emerge from the burrow until a body weight of approximately 1.3kg and a dried eye lens weight of about 175mg were attained. There are data to sug- 3est that the lactation period was about seven weeks and that spring- hares were weaned soon after they began life above ground (Section Three). Age at first emergence from the burrow is therefore estimated to be about seven weeks. A similar case of "incomplete precocity" has been described by Weir and Rowlands (1973) for some members of the ro- dent suborder Hystricomorpha. The selective advantage of the neonate's well-developed state at birth, and its long stay in the burrow, are not apparent (Van der Horst 1935; Hediger 1950). However, it has been sug- gested (Section Three) that this may be a predator-avoidance procedure, the neonate avoiding burrow entering predators by ranging widely within the large burrow system and by prolonging the time before it becomes available to the many above-ground predators (see below). Estimating Foetal Age From 200 records the gestation period of the springhare has been estimated at 80-82 days (Rosenthal & Meritt 1973) and 72-82 days (Velte, in press). A gestation period of 77 days is recognized here. The weight h’of foetal springhares can be predicted from their ages t using the equation of Huggett and Widdas (1951), Wl/3 . a(t - to). To determine foetal age from foetal weight the equation can be re- written a 62 This equation is based upon the linear relationship between the ‘weight of the foetus and conception age. Use of the equation requires knowledge of the body weight W and age t of one foetus and, as such, birth weight and gestation time are most commonly used. The constant to indicates the approximate age at which linear growth of the foetus commences and is derived from the equation t - (0.3) (t8) for mammals O with a gestation period tg between 50 and 100 days (Huggett & Widdas 1951). Therefore, in the springhare, t = 23 days. Using a gestation 0 period of 77 days and a birth weight of 2523 the Specific foetal growth velocity a is calculated to be 0.117. The equation for predicting the age of foetal springhares in days, based upon the weight of the foetus in grams, becomes: 0.117 Alternatively, by calculating W1/3 for each foetus, the conception age can be estimated by using the graph in Figure 12. Here to = 23 days 1/3 3 provides the first fixed point and tg 8 77 days, and its ordinate, W 6.33, provide a second fixed point. The majority of species examined by Huggett and Widdas (1951) showed foetal growth velocities between 0.15 and 0.05. The foetal growth velocity of the springhare (0.117) lies well within this range. The age of each foetus was estimated using the Huggett & Widdas (1951) equation. The simple linear relationship between the length of the foetus.f and the age of the foetus t can be expressed by the equa- tion (Figure 13): t - 0.15 (r) + 26.94. The correlation coefficient (r = 0.992) is highly significant (P ‘< 0.0005), indicating that the length of the foetus can be used with 63 '7. 6F 51 4 . 3' S’ E 3 ~ .9 Q) 3 1’; o 2’ 0:1 33 8 p; I L 0 r¢ f9-1b __., e Gestation Period (days) * Figure 13. Cube root of the weight of the Foetal springhare plotted against age. The linear relationship W = 0.117(t-23) can be used to estimate the aye t of the foetal springhare in 7 days [or any foetus of known weight 3. See text for details. 64 320!- A- 340 A“A 300.. a «320 AA , 280~ I It. 4300 A .' 260- u A ‘ § ’ «280 240” s . .. 99 .3 26° 220” 63k ‘ .’ .240 .- 10‘ o 200 x. f . I .220 :3: I80- I‘ . 1200 ‘ l :5, l60- ‘ I .. I80 '6 140. Length . . ' . l60 B a ,- Izo- - « I40 4‘ I :00- u‘ / . :20 I so- 4‘ « IOO .2 1' Weight 60" ‘~ '. " 80 ‘ o 40» ‘3“ . ’ - so 20. .o"'./ - 40 ._L_:!:;!-'..‘T‘. I J 1 1 2C) 2832364044485256606468727680 Age of foetus (days) Figure 13. The relationship among body weight (O,n=98), overall length (A, n=96), and the age of foetal springhares. See text for details. Overall length (mm) 65 confidence for estimating its age. External Measurements Five growth-parameter means, standard deviations, sample sizes, and overall coefficients of variation were calculated for male and fe- male foetuses at each of 15 categories of body weight (Tables 6 & 7). The growth rates of the body parts of male and female foetuses, as they relate to body weight and approximate age, were similar. The coeffi- cients of variation indicate that the male sample was no more variable for any one of the five body parts measured than was the female sample. In both sexes, ear length Showed the greatest variability, followed by hind foot length, tail length, body length and forehead-rump length. Linear regression equations describing the growth rate, relative to body weight, for each of five body parts of male and female foetal springhares were derived (Table 8). Comparison of the regression slopes b indicate that the rate of change of all five body parts, relative to body weight, was similar for both males and females. These values also indicate that for each unit change in body weight, body length exhibited the highest growth rate, followed by tail length, forehead-rump length, hind foot length, and ear length. The slopeslb and correlation coef- ficients:r were positive and highly significant in all cases (I’< 0.001). The coefficients of determinationzr2 indicate that, except for forehead-rump length in males, more than 78% of the variability in a given body measurement was correlated with variation in body weight. The relatively low 1’ and r2 values for forehead-rump are probably due to, and may indicate the extent of, error inherent in making this measure- ment . 66 Table 6. Means and standard deviations 8.0. of growth parameters for male springhare foetuses for each 203 category of body weight. d g :5 o' a’ a' J: . . . A . .3 . 1.1 U) H m :- m E U) u (n 'U 00 I A U U E 00 3 A 5’s“ 85" SA“ 8"“ 53“ g g g. >nE’E ‘3 m -41§44 .g~v-+l _g E +l .L.fi +| .41544 w-I CB 10 ‘3 00 00 C- N >~ C U C V C '6 00 C H S 31 3 8 7.3" SE B 8 3 8 I: 8 5 5 8 '3 3 In.) 3 W 2 3: In I: I") I: = H I: [- I: 41-49 10-29 6-7 86 1 16 5!. + 11 6 1 2 15 1 z. 32 1 10 50-54 30-49 a 141 1 13 74 1 5 12 1 2 26 1 3 57 1 6 55-58 50-69 3 183 1 16 93 1 7 17 1 3 35 1 77 1 7 58-61 70-89 4 200 1 12 97 1 11 19 1 2 39 1 2 85 1 7 61-64 90-109 8 223 1 5 106 1 8 21 1 1 46 1 2 96 1 3 64-66 110-129 3 243 1 5 120 1 7 25 1 1 52 1 3 106 1 1 66-68 130-149 3 264 1 14 118 1 12 29 1 2 57 1 3 118 1 11 68-70 150-169 0-1 299 1 0 - 29 1 0 67 1 0 127 1 0 70-72 170-189 1 291 1 0 118 1 o 31 1 0 66 1 0 126 1 0 72-74 190-209 1 301 1 0 11a 1 0 3a 1 o 67 1 0 132 1 0 74-75 210-229 1 302 1 0 111 1 0 33 1 0 7t. 1 0 135 1 0 75-77 230-249 1 310 1 0 11.1 1 0 33 1 0 75 1 0 14.5 1 0 77-78 250-269 - - - - - 78-80 270-289 1-2 333 1 2 155 1 0 a1 1 a 84 1 z. 146 1 6 30-81 290-309 2 336 1 8 155 1 1 39 1 3 87 1 5 159 1 9 Overall c.v. 00* 37.33 30.12 48.12 47.60 41.98 *Coefficient of variation. Table 7. 67 Means and standard deviations 5.0. of growth parameters for female springhare foetuses for each 203. category of body weight. 3 313‘ .S.n. .3 o " E +I '§'~I+' 'g‘§-+l «3.5 +| fiIigqq :98 fig. 3.3 5"; 1: 8 .. 8 888 :vs a: .6 5 m .8 z 3 £1 8 é’ E 3 2 S 1’ 41-49 10-29 6 91119 53 1 9 6 1 3 16 1 4 33 1 7 50-54 30-49 S 138 t 10 75 i 5 12 i 1 26 j; 2 56 j: 6 55-58 50-69 5 180 1 3 88 1 8 17 __ 1 35 1 5 75 1 3 58-61 70-89 6 202 1 11 98 1 12 22 1 1 40 1 2 86 1 6 61-64 90-109 2 230 1 5 117 1 1 24 1 1 47 1 1 98 1 4 64-66 110-129 4 239 1 10 117 1 12 25 1 1 so 1 1 103 1 7 66-68 130-149 1 260 1 o 125 1 0 28 1 0 55 1 0 112 1 0 68~70 ISO-169 0 - - — - - 70-72 170-189 2 283 :_10 115 + 0 3O :_1 66 :_1 130 i 6 72-74 190-209 3 286 $.15 88 + 6 31 :_2 63 :_3 129 t’7 74-75 210-229 0-1 311 i.0 133 + 0 36 1,0 78 i_0 - 75-77 230-249 1 306 1 0 150 + 0 33 1 o 72 1 0 139 1 0 77-78 250-269 0-1 330 i 0 140 + 0 35 j; 0 79 i 0 - 78-80 270-289 1 320 :_0 126 + 0 38 :_0 84 t’O 145 i’O Overall C.V. (%)* 36.03 32.13 47.39 46.02 40.73 *Coefficient of variation 68 Table 8. Coefficient constants a and b,and correlation coefficients r for the linear regression of five body measurements I of male and female springhares on body weight X in grams. Size of samples as in Tables 6 and 7. Dependent Intercept Slope constant Correlation Coefficient of Variable constant b“ i_1$.E.*** Coefficient determination 3‘ a r r2 Body length (mm) 129.9 0.090 1 0.006 0.9270 0.8593 Tail length (mm) 51.4 0.044 i_0.003 0.9323 0.8691 Forehead~rump length (mm) 70.0 0.034 :_0.003 0.8867 0.7863 Hind foot length (mm) 22.0 0.026 1 0.001 0.9711 0.9431 Ear length (mm) 10.2 0.012 :_0.001 0.9494 0.9013 FEMALES Body length (mm) 127.0 0.093 t 0.006 0.9420 0.3874 Tail length (mm) 48.8 0.047 1.0.003 0.9404 0.8843 Forehead-rump length (mm) 71.8 0.028 :_0.005 0.6759 0.4568 Hind foot length (mm) 21.8 0.026 1 0.001 0.9748 0.9502 Ear length (mm) 10.5 0.012 1_0.001 0.9312 0.8671 *Y - a + b (X). See Method Section for details. **Probability that the slope b is not significant from zero is <0.0005 in all cases. ***One standard error. 69 External Morphology Except for a detailed description of the external characteristics of a single foetal springhare thought to be full term (Jones 1941), foetal development in this species has not been studied. From a sample of 153 preserved embryos and foetuses, a representative series of 22 was selected and the major discernible chronological changes in external mor- phology noted (Table 9). Foetal vs. Maternal Weight Based upon the relationship between maternal weight and total weight of newborn young in 114 mammalian species, Leitch, Hytten, and Billewicz (1959) derived the following equation for predicting the to- tal weight of young carried at full term: N - 0.540811 0'83” Here N is the weight of the newborn litter and.M is the weight of the mother, both in grams. The mean weight of 182 adult female springhares, minus the mean weight of the foetuses, was 3020g. Using this figure as the weight of the mother, the predicted weight for newborn springhares is 426g or 14.1% of the mother's weight. Since the mean observed birth weight is 252g, the predicted birth weight of springhares is 174g (69%) greater than that observed. Leitch et al. (1959) also showed that the smaller the mammalian species the greater the weight of the newborn young relative to that of the mother. They found this generalization to be true for total weight of young, whether the birth be single or multiple. The mean weight of the newborn springhares was 8.3% that of their mother. 0f the 26 spe- cies of rodents on which Leitch et a1. (1959) performed similar calcula- tions, only the grey squirrel Sciurus carolinensis (8.1%) and the 70 ABE—v aqua mosoooa Hana no nxm Hmumuv “menu can and: .onmc .numu so wcuwuoau mom 680— ¢_~ co ozo no houses as >Hco nacho Iwuousm gamma on no wcuwuoau you saw. acouxo mououusc mono moumz no co >mum voucosmwa r umunuv .qmcuouxo .ohu mo m uo>ou saw on :umou mo~oaas< on an unheaou smomu wcuaoomn monogamuaos Hmuaonoo comm cogs cameos soon was: as mm was: no nos uo>o ASSNV nozuo sumo no“: manumu> mmuqm Ham scum uumucou oxma oomw as nausea nowsod o: scuumsao> mcuwuoeu ommmuunu> haouna mo~uwus< memo uOOu on“: m~ me moon on: lane on unseen muom nuoca manuzwumm wad Ivsuuoua uanOu .aono scam nmnu susoa "vouoaoo amsuu momm«un«> o>o no usuuozm uoOu monogamuau: Hangoumo saxm :wsouSu huummau wcqwuoeo o: .mouum mmcuou heuumumoa mam: “mafia sod can aucuumqv noususm comm maommo> moods ago so acomoun sumo» vco mousse Idmsm mm ucomoun Honouoo use amuuuwmm acme “sou anon oz mo~o«-0u ommmuua«> twins: moduuus< van canoao mono: nu we Aasv you mass mo Aasv ommmwunw> Amy Amhva susoe :uwcmm ecu zusouw unuumomaa mo uoOu new; uswums own one :3ouo new .sowuoc«o> nuwcufi a omnmuuow> monouus< van moumz Hmuoom .xouan< .mumswcqumm umuoou ago :4 unuanoau>sv was swabs” uo suuuusm .a munch 71 Ana nae oaoauau no owcuuu ouwuco macan mcawuoao mum: "dame was easy .xumn .wnms .saouo co haw mamas mason nu monsoon nusouw usu mummy huo> Aescv asses co cyan: vououumom .xonn so any Jonas uocfiumuv «vacuums no n\_ Hmawxoum «mmuov so momuosu ash naawv vmmnouOu wsuvsuuoun so now goods can scum camcou snowman .nssu use was: .ssouo muomuucq mouowmu> so use sauna mo susouw nowcoa o: monsoon mucuumqv «macaw a sump assouou vcm Hmuuuwmm .aumu co wcumuuem ssh any» commas lawn noaouusm ea QN no «\N dosage .umsuuuxm BE NN «nN as oo— oh had we 135 you mean no canoe auwsoq can susouw can szouo new .so«umsno> Aasv ommmnuau> unassumza uo guacag a mmmmuuaw> moaouusd Amy Aaaaev usmuos own Augean .xounnd .A.v.u:00v m macaw 72 porcupine Erithizon dorsatum (8.0%) had lower relative weights. The nutria Myocaster coypus, with a body weight 65% greater than that of the springhare, produces young with a relative weight of 22.4%. Both the absolute weight of the newborn springhare and its weight relative to that of its mother were, therefore, considerably lower than predicted' from the formula of Leitch et al. (1959). SECTION FIVE REPRODUCTIVE ACTIVITY IN THE MALE SPRINGHARE INTRODUCTION In a preliminary review of the subject, it was found that the sea- sonal reproductive cycle had been studied in approximately 46 species of African rodents (Brambell & Davis 1941; Chapman, Chapman & Robertson 1959; Hanney & Morris 1962; Delany 1964a, b, 1971, 1972; Hanney 1964, 1965; Coetzee 1965; Happold 1966, 1967, 1970, 1975; Smithers 1966, 1971; Dieterlen 1967; Neal 1967 in Delany 1972, 1970; Rahm 1967, 1970; Bellier 1968; Delany & Neal 1969; Jarvis 1969; Chapman 1972; Van der Horst 1972; Kingdon 1974; Field 1975). Of these, 18 species reproduce during all months but undergo seasonal peaks in breeding activity. Only four spe- cies, springhares Pedetes capensis (Smithers 1971), unstriped grass rats Arvicanthis niloticus (Delany 1969), soft-furred rats Praomys jacksoni (Delany 1972) and Boehm's squirrel Puraxerus boehmi (Rahm 1970) repro- duce year round, and possibly exhibit no relationship between reproduc- tive activity and season. Nearly all of the above studies stress reproductive activity in the female. The seasonal reproductive cycle of the male was investi— gated in only seven rodent species. These exhibit a variety of repro- ductive patterns. Cape mole-rats Bathyergus suiZZus cease spermato- genesis during part of the year (Van der Horst 1972). Lesser pouched rats Beamys major undertake spermatogenesis during all seasons but show changes in testis size and in the extent of the spermatogenic 73 74 activity (Hanney & Morris 1962). Multimammate rats Mustomys natalensis and brush-furred mice Lophuromys fiavapunctatus exhibit seasonal changes in testis size and spermatogenesis in some localities (Hanney 1965) and no seasonal reduction in reproductive activity in others (Coetzee 1965; Neal 1967; Delany 1971). Only Mus triton, spiny mice Acomys cahirinus (Hanney 1965), and soft-furred rats Praomys maria (Delany 1971) show no seasonal changes in testis size or spermatogenesis. There exists considerable variation in the timing and/or degree of reproductive activity between the sexes. In some species the female reproduces seasonally while the male, although showing seasonal peaks in sperm production, is capable of reproduction at all times. In others the female may exhibit seasonal peaks of fertility while the male dis- plays a constant level of sperm production and no testicular regression. It is evident that the seasonal pattern of reproduction in the male ro- dent cannot be necessarily inferred from that of the female (Chapman 1972). The reproductive pattern of the male springhare has not been in- vestigated in detail. Smith (1965) provided measurements on the repro- ductive tracts of 13 male springhares in Rhodesia. Coe (1969) in Kenya described the gross morphology of the reproductive tract. Data on sex and age ratios for two populations of springhares and on growth of the male springhare are presented in Sections Three and Five, respectively. This section examines growth and development of the reproductive tract of male springhares and presents data on their reproductive ecology in the Republic of Botswana. This section was inspired by the paucity of knowledge on male African rodents and by the opportunity to work on a species which appeared to exhibit no seasonality in breeding activity despite a strongly seasonal environment (Smithers 1971). 75 MATERIALS AND METHODS A total of 165 males were taken on the Kalahari Study Area and 119 on the Eastern Study Area during 24 consecutive months. The mean monthly sample size from September 1971 through July 1973 for both areas combined was 12.3 i 1.0 males. In addition, two were collected in August 1973. There was no indication that male springhares from the two study areas differed significantly in either the morphology of their reproduc- tive tracts or their reproductive ecology. Data for the two study areas, therefore, were combined. Body weight was measured to the nearest gram, and right testis, right epididymis, and right seminal vesicle weights were taken to the nearest decigram (dg). Bacula were removed and placed in hot 5% potassium hy- droxide for about three hours as the solution cooled. They were then cleaned with a scapel, oven-dried to a constant weight, and weighed to the nearest milligram. The length of the right testis, right vas defe- rens, and baculum, and the distance from the tip of the penis to the junction between the vas deferentia and the anterior border of the urine- genital sinus all were measured to the nearest millimeter. Excepting eye lenses and bacula, all materials were measured while fresh and then placed in 10% formal-saline. After fixation the testes and epididymides were dehydrated, em- bedded in paraffin wax, sectioned at 7um, and stained with Ehrlich's haematoxylin and eosin. Stained sections of testes were examined mi- croscopically for the presence of spermatozoa and, in all cases, where autolysis did not prevent it, mean seminiferous tubule diameters were 76 obtained using a calibrated micrometer eyepiece. For the purpose of this study, springhares were classified as "immature" if the testis showed no histological signs of spermatogenesis, and "mature" if spermatozoa were present. Confirmation of the "mature" classification was obtained by the presence of spermatozoa in the epididymides. "Rainfall" is the mean monthly total rainfall for both study areas combined and is based upon readings at Lephepe, Letlaking and Gaborone (Botswana Meteorological Services). "Temperature" is the mean of the daily maxima and minima air temperature for each month (Botswana Meteorological Services). "Day length" is taken from Smithsonian Meteoro- logical Tables (List 1966) and represents numbers of daylight hours at mid-month. RESULTS AND DISCUSSION Development of the Reproductive Tract Means and coefficients of variation were calculated (Table 10) for 12 measurements of the reproductive tract of male springhares as they relate to eye lens weight (relative age). Testes only increased about 0.3g (Figure 14b) from birth, when the neonate weighed approximately 250g and had an eye lens weight of about 80mg, until a body weight of approximately 2.2kg and an eye lens weight of about 275mg were achieved. The reproductive tract underwent little growth during this period. There was a sudden and rapid growth of the reproductive tract, however, associated with attainment of puberty (Table 10). With a change in eye lens weight from.275mg to 400mg there was a 20-fold increase in testis weight (Figure 14a) and a three-fold increase in baculum weight (Figure 15a) and seminiferous tubule diameter (Figure 15b). The penis was not evertible by the live animal until the rapid growth phase of the reproductive tract commenced. 77 Table 10. Means x, coefficients of variation C.V., and sample size n for 12 measurements from the reproductive tract of the male springhare as they relate to dried eye lens weight. Dried eye Approx. Right Left Right Left lens body testis testis testis testis weight (mg) weight (dg) weighs (dg) weight (dg) length (mm) length (mm) n r C.V.: n r C.V.% n .3 C.V.S n : C.V. ISO-174 1.02 1 3 - 1 3 - 1 16 - 1 16 - 175-199 1.54 8 4 23 5 5 12 8 16 18 5 16 23 200-224 1.76 9 4 23 6 4 28 10 17 19 7 16 22 225-249 1.95 8 4 24 6 4 28 8 16 15 6 17 11 250-274 2.11 12 5 29 10 5 34 12 17 18 10 17 18 275-299 2.27 19 14 130 10 20 127 20 23 39 11 25 46 300-324 2.46 17 21 139 10 23 113 17 26 38 10 29 37 325-349 2.53 14 50 74 9 45 79 14 36 27 9 35 31 350-374 2.66 22 92 40 11 103 36 23 48 15 12 49 11 375-399 2.72 22 99 35 12 102 19 22 52 10 12 51 8 400-424 2.78 16 105 30 7 122 32 16 50 11 7 54 10 425-449 2.82 29 132 21 11 126 28 30 54 15 12 53 23 450-474 2.88 18 135 26 9 143 33 18 54 9 9 55 14 475-499 2.94 15 141 20 8 153 21 16 55 11 9 56 10 $00-$24 2.98 15 161 18 10 176 13 17 58 6 12 61 7 525-549 3.07 16 149 29 ‘ 8 161 27 17 57 10 9 S6 13 550-574 3.14 8 132 31 4 124 41 8 55 11 3 54 20 575-600 3.20 12 156 35 6 190 19 12 58 11 6 63 8 600-624 3.20 5 162 18 1 197 - S 61 6 1 62 - 625-649 3.20 2 160 41 1 102 - 2 64 14 1 53 - Table 10 (cont'd.). 78 Dried eye Right vas Left vas Right Right lens deferens deferens epididymis seminal vesicle weight (mg) length (mm) length (mm) weight (dg) weight (dg) ' n :2 C.V.: n a’: C.V.: n 5 C.V.: n 5 C.V.: 150-174 1 74 - 1 72 - 1 4 - 1 1 - 175-199 5 78 9 5 77 8 4 3 35 3 2 35 200-224 7 78 18 6 74 13 5 3 23 5 2 61 225-249 6 94 21 6 94 13 4 3 58 2 2 0 250-574 8 89 21 10 88 19 7 4 79 4 2 23 275-299 10 108 17 11 106 17 5 10 90 4 10 136 300-324 9 113 17 9 114 16 7 10 64 4 S 60 325-349 9 130 22 8 137 24 10 24 63 4 36 68 350-374 12 154 12 11 154 12 9 36 25 10 40 45 375-399 11 149 21 11 147 25 12 37 27 12 56 54 400-424 7 171 8 6 161 8 8 44 23 6 83 34 425-449 12 149 19 12 148 20 11 47 23 8 54 49 450-474 9 146 19 9 149 18 3 58 19 3 47 53 474-499 9 153 13 9 155 8 4 44 23 5 65 17 500-524 12 170 5 12 171 6 9 53 20 6 82 46 525-549 9 162 3 9 159 14 4 54 18. 6 81 24 550-574 4 169 7 4 174 7 4 53 32 3 81 17 575-599 5 173 5 5 172 6 3 62 12 5 53 51 600-624 1 182 - 1 178 - 1 52 - 1 54 - 625-649 1 164 - 1 171 - 1 51 - 1 80 - Table 10 (cont'd.). 79 Dried Dried eye Seminiferous Penis tip to baculum weight Baculum length lens tubule diam.( m) was deferentia (mm) (mg) (mm) weight (mg) n E- c. v. z n E C.V. z n E.- c. v.1 n E c. v. 3 150-174 1 52 - 1 100 - 1 6 - - - - 175-199 8 46 10 5 113 18 6 10 52 6 15 8 Zoo-224 a as a '6 120 21 10 10 34 s 1:. 30 225-249 3 46 11 5 110 3 9 9 69 6 14 23 250-274 11 52 40 7 114 10 14 11 69 10 16 15 275-299 17 70 49 10 130 13 17 24 80 16 18 18 300-324 12 72 36 9 143 11 16 33 79 16 19 20 325-249 10 123 37 9 143 16 15 77 63 13 18 23 350-374 19 170 15 11 172 8 20 99 40 21 25 9 375-399 20 180 11 12 174 5 24 115 28 22 28 30 400-424 13 176 14 7 185 6 15 134 32 16 27 8 425-449 25 183 11 10 178 5 29 154 24 29 28 6 450-474 16 177 12 8 151 30 17 165 22 17 28 5 475-499 13 182 12 9 182 10 15 168 26 15 28 6 $00-$24 15 194 14 11 177 19 17 168 23 17 28 6 $25-$49 14 187 17 9 183 8 17 155 23 16 28 5 $50-$74 8 181 14 4 187 12 8 150 30 8 27 5 $75-$99 7 180 11 6 189 4 12 181 19 12 28 5 600-624 3 212 20 1 181 - 5 193 3 5 30 4 625-649 1 200 - 1 192 - 2 192 13 2 28 7 80 § § 1 O R .5 u 8 I I I Tesm venom (O In) 8 I 3 3 6 8 t 4.1 +0: ? O |~ 8 8 l l 8 I 3 8 6 4 6 + —*—o I?) +0! —~ A U. I Testis length (mm) u an I N U! T |u '- +0 6 _+o :3 + 0| I u U! r O N 0 u. u 0‘ O I 8 5 I .3 —¢—-5 6 3 3 K: + a: a: + —*—u *N Efils- :09 £20- + 3 _ "I5- 3 E 8 ' .L .3 t g .3 é |.O'- - a. g 3 g g 05-: E g g. 45 b; 3 %o l l l l l l l l l l J I I50 250 350 450 550 650 Eye lens venom (m) Figure 14. Changes in (a) right testis weight, (b)right testis length ' and (c) body weight of male springhares relative to dried eye lens weight (range = thin vertical line; mean = horizon- tal line; standard error = broad vertical line). Size of sample given above each range. 8] , I7 24OF- '5 8 l2 0 29 I? E 200'- 20 24 '5 ; <' E; _ IS a 3 IGCH' i} E _ i .2 3 120- 8 1 .. 1 8C)“ l7 40r l4 _| 6 IO 9 L - 4*f+'*L1 1 1 1 1 1 1 1 1 E '3 3 1250'. b '5 g ZCK)_' 'éfi' ICE 1} - .9 3 o. 't 'o g ‘5 g :50 ~55» 8 :2 § 3 °>’ 12% a o o! «- ‘3 I00 4’ 5 3’3 e n i % .9 '- 7 'E l_ 7 9 'éw’++* 1 8 O l l l l l l l l l J I50 200 250 300 350 400 450 500 550 600 650 Eye lens weight (mg) Figure 15. Changes in (a) baculum weight and (b) seminiferous tubule diameter of male springhares relative to dried eye lens weight (range = thin vertical line; mean = horizontal line; standard error = broad vertical line). Size of sample given above each range. 82 Body weight, testis weight, testis length and baculum weight changed little (Figure l4a,b,c, 15a) after an eye lens weight of 425mg was reached. The seminiferous tubules ceased growth in diameter at an eye lens weight of about 360mg (Figure 15b). As expected, the coefficients of variation (Table 10) showed the highest values during the rapid growth phase of the reproductive tract. The weight of the seminal vesicles was particularly variable relative to eye lens weight. Testis length, baculum length, distance from penis tip to vas deferentia, and seminiferous tubule diameter exhibited the lowest variation relative to eye lens weight. Testis length, seminiferous tubule diameter, and dried baculum weight were highly correlated with testis weight (Figure 16). Puberty Overall, seventy-two percent of the male springhares exhibited spermatogenesis. Spermatogenesis began at that time when the growth rate of the reproductive tract was greatest. For body weight, eye lens weight, testis length, baculum weight and seminiferous tubule diameter, the smallest value associated with the presence of sperm, and the lar- gest value associated with the absence of sperm, was determined.(Table 11). These values indicate ranges of overlap within which prepubertal and postpubertal individuals both occurred. For a particular body part, spermatogenesis occurred in individuals with values below this range, whereas puberty had been achieved by all individuals with values above this range. Baculum weight and seminiferous tubule diameter (Table 11) showed no overlap of prepubertal and postpubertal individuals. For testis length and weight the overlap was only 3.32 and 0.2%, respectively. .cH space :w mm mmaeEcm mc mmww .wccwumzcm cowmmmuuop oLu oumpchsc Cu com: scoB .mccve so: .mumc #mzuw>wv:~ .uswwoB mco— oxo rowan we zpcuoumo wEmN Loco cw moeccxcwsem man Lou asww03 mwumou umcwnwm fiuwcoa mwumou uzwwu can .uzuwos Ezmzonn comet .pouwenwc m~:£:u mzcumuwcwEom :mmE mo muopm .o~ musuwm a. .9 29...; £848.. o.~ m... o._ no 0 _ 1 _ 1 6.0 o_ .| «080.9 VG .WQNuC .NVQ.O«.: _| . no.8 . o. .m 315+ 36 on» 8. 1 mo m 22o: 6238 m, ON I m. 308.0 K £52656": 1 ~.. .4 mu 0. my w. on 1 8.782 8.8.» o 6 5083.8» w m m m 9.1 ) m, m 1 m ( 8 I o \ o a same 0 o \e\\ o . a \+\+..ma \\fl.\ . Gooo.ova.om~.c.§m%t. 1 _ N W 8 6:1 . 1 mm: + xeoo. canon» 8. m assay 23.: 1 an w 2. r: L N.N m 84 Table 11. Summary of spermatogenic activity of 264 male springhares as it relates to measurements of six body parts. See text for explanation. Size of samples as in Table 10. Overall Largest with- Smallest Overlap Z overlap Variable range out sperm with sperm range c - d (a) (b) (e) (d) (c - d) b - a Body weight (kg) 1.25-3.60 2.82 2.33 0.49 20.9 Eye lens weight (mg) 158-631 344 281 63 13.3 Right testis length (mm) 9-70 35 33 2 3.3 Right testis weight (8) 3-213 2.5 2.1 0.4 0-2 Bacula weight (mg) 4-254 41 41 0.0 0.0 Tubule dia- meter (um) 7-264 111 117 0,0 0.0 85 Thus, a testis length of 34mm, a testis weight of 2.3g, a dried baculum weight of 41mg, and a seminiferous tubule diameter of 114m can be used with a high degree of confidence to separate prepubertal springhares from postpubertal springhares. In contrast, the overlap value for body weight indicated that both prepubertal and postpubertal individuals occurred over 20.9% of the range of body weight observed for juvenile and adult male springhares. For eye lens weight the overlap value was 13.3%. The eye lens weight or testis size at which mating actually first occurs is not knowh. Breeding,Season Neither seasonal atrophy nor senscence was observed in any part of the reproductive tract. All males with a testis weight greater than 2.5g exhibited spermatogenesis. Least squares linear regressions of monthly mean testis weight and seminiferous tubule diameters of adult male springhares on monthly rain- fall, air temperature and day length (Table 12) showed no significant correlations (P > 0.3). An analysis of variance between month of collection and right and left vas deferens length, right and left testis weight and length, and right vesicular gland weight (Section Three) indicated that there was no interaction (P > 0.3) between size of the reproductive tract and time of year. The evidence clearly shows that the fecundity of this popululation of male springhares was largely unaffected by seasonally-occurring phe- nomena. It is well to recall the comment of Chapman (1972) however, that "...a continously fecund male mammal may also be a seasonally breeding one." Thus, while the presence of spermatozoa in the male 86 Table 12. Monthly values for mean testis weight and seminiferous tubule diameter of adult springhares (eye lens weight > 350mg) relative to monthly total rainfall, mean air temperature, mean forage protein and mid-month day length. Month Right testis Tubule Sample Rainfall Air Forage Day weight (dg) diameter (um) size (mm) temperature protein length 3; 1 s.1-:.* 1 1 5.5.. 72“! (c0) (2) (h) Sep 199 :_O 203 $.14 1 3O 21 13 12.0 Oct 98 :_19 169 :_11 5 $7 22 15 12.8 Nov 139 $.17 187 :_9 3 147 23 17 13.4 Dec 141 i_12 186 t’ 5 45 25 17 13.7 Jan 146 :_20 178 :_ 5 268 24 13 13.6 Feb 145 :_15 194 t|16 5 40 24 13 13.0 Mar 137 1; 8 202 1 5 57 23 17 12.2 Apr 130 $.25 185 i. 6 10 21 14 11.5 May 128 i 20 208 1 4 1 16 11 10.9 Jun 85 3.33 178 3,16 3 0 13 12 10.6 Jul 121 1’17 196 1,7 6 13 11 10.8 Aug 149 j; 13 208 i 8 11 16 10 11.4 Sep 142 1,14 218 3’10 11 18 20 11 12.0 Oct 138 $.15 192 :_6 13 25 12 12.8 Nov 146 :_14 184 :_6 21 25 18 13.4 Dec 102 i. 176 1,9 10 26 28 17 13.7 Jan 130 t. 165 1,4 11 36 29 20 13.6 Feb 128 3’ 168 i.“ 10 68 26 17 13.0 Mar 109 i 11 156 i 3 13 26 27 17 12.2 Apr 129 i_12 166 :_$ 10 32 20 17 11.5 May 114 1,11 152 :_3 12 1 17 18 10.9 Jun 141 i 12 194 -_l-_ 11 11 O 15 13 10.6 Jul 122 i 12 180 j; 7 17 0 14 12 10.8 Aug 132 :_0 - 1 0 16 16 11.4 *1 standard error of the mean. MSample size of right testis. 87 springhare may indicate a year-around fecundity, it does not neces- sarily mean a year-around reproduction. Of 199 adult females collected during this 24 month study, 76% were pregnant. Among 130 adult females examined for lactation, 96% were pregnant and/or lactating, and 79% of the non-pregnant adult females were lactating (Section Three). There was no evidence of a seasonal pattern in the percentages of females preg- nant. An analysis of variance (Section Three) did not show significant interactions GP > 0.06) between month of collection and right or left ovary length, vaginal length, nor body weight of females or foetuses. The springhare population as a whole, therefore, showed no annual peaks in reproductive activity and exhibited an unusually constant reproduc- tive effort throughout the year. While mating occurred in the springhare population during all months, no positive evidence was found indicating that the individual male springhare did not undergo a seasonal or periodic sexual cycle. If such was the case, however, the cycle was not synchronized among males in the population, and it was expressed as only a slight reduction in size of the testis and/or seminiferous tubules. SECTION SIX BIOMETRIC ANALYSIS OF BODY AND ORGAN GROWTH OF THE JUVENILE AND ADULT SPRINGHARE INTRODUCTION Except for the first few weeks after birth (Hediger 1950; Coe 1967; Rosenthal & Meritt 1973; Velte, in press), there is no published account concerning the growth characteristics of the springhare. This section provides representative data on body and organ measurements of normal healthy juvenile and adult springhares, examines body and organ growth patterns and relationships in springhares, and com- pares these growth data with those for several other mammalian species. MATERIALS AND METHODS Although springhares collected on the Kalahari Study Area were slightly larger than those from the Eastern Study Area, these differences and the purpose of this analysis did not warrant their separate consi- deration. Springhares in Botswana bred year around and breeding peaks or changes in body weight were not apparent (Sections Three & Five). There- fore, annual changes in body weight resulting from pregnancy or changes in body condition were not important complicating factors in the present study. Springhares were weighed to the nearest gram. External length measurements were taken to the nearest millimeter. "Tail length" is the distance from the upper base of the tail to the tip of the tail, not 88 89 including the hairs; "ear length" is the length of the right ear from the notch at the lower end of the ear opening to the tip of the ear; "hind foot length" is the length of the right hind foot from the heel to the end of the middle toenail; and "body length" is the distance from the tip of the nose to the end of the tail, not including the tail hairs. Testes, vas deferentia, ovaries and vaginae were measured to the nearest millimeter. Heart, liver, kidney, testis, and seminal vesicle weights were taken to the nearest decigram (dg). External fat was re- moved from all organs prior to weighing. In juvenile and adult springhares the weight of the dried eye lens ranged from 158mg to 631mg. This range was divided into 50mg increments and each of the 560 springhares was assigned to one of the ten resulting categories. Body and organ measurements were tabulated and subjected to statistical analyses using the CDC 6500 Computer at Michigan State Uni- versity. Means and standard error of the means were obtained for six- teen parameters on males and twelve parameters on females in each of the ten categories of eye lens weight. Regressions were used to analyse the growth rate of various parts of the body relative to eye lens weight. Relative growth rate values were obtained from the regression coefficient b in the linear regression equation Y = a<+ b(X) or from the coefficient b1 in the quadratic regression equation Y=a+b1X+b2X2 The b1 coefficient alone provided a suitable index of relative growth rate since the b2 coefficient was always small and contributed little to the slope value. 90 In the linear and quadratic regression equations Y is the weight or length of a body part, a is the intercept constant, and X is the dried eye lens weight in milligrams. The b and b1 coefficients are, therefore, the rate of increase of the dependent variable Y (3.9., body length, heart weight) relative to that of the independent variable X (eye lens weight). Although in most cases both linear and quadratic equations provided satisfactory predictive values for the variable under considera- tion, the equation yielding the higher correlation coefficient was chosen for presentation here. In mammals the weight and length of body parts are frequently re- lated to total body weight through power laws (allometry) (Huxley 1932; Gould 1966). Statistical analysis reveals that allometric equations are reliable for estimating organ weights in animals ranging in size from mice (25g) to steers (lOOOkg) and possibly they also apply in elephants and whales (Brody 1945; Stahl 1965). In this study the allometric pre- dictive equation Y-aXb was used. Brody (1945) considers this to be the most satisfactory equa- tion for relating part-to-part or to body weight in animals of different size. Y'is the weight or length of a body part (dependent variable) and X'is the body weight (independent variable). b is the growth ratio at which E'increases relative to x, and is here referred to as the "constant of allometry" (Simpson, Roe & Lewontin 1960). Thela coefficient denotes the value of y when Kb equals 1 and is called the "initial growth con- stant" (Teissier 1960). a and b were calculated by the least squares regression of loglo -transformedy and X variables (Brody 1945; Simpson et al. 1960. 91 Differences between means and regression slopes were tested with Z- and F- statistics, respectively. Significance of the regression slopes and correlation coefficients were determined by F- and t- statistics, respectively. A value of I“<0.05 was regarded as signifi- cant and P< 0.01 as highly significant. The statistical references con- sulted were Steel and Torrie (1960), Sokal and Rohlf (1969), and Gill (1977). RESULTS AND DISCUSSION Body Measurements The overall coefficients of variation C.V. for juvenile and adult springhares (Tables 13 & 14) indicate that external length measurements were not highly variable; the largest coefficient of variation being 8.7% (female body length). Length measurements of parts of the repro- ductive tract exhibited far more variability; the coefficient of varia- tion ranged from 18.0% for vagina length to 42.1% for left testis length. Body weight had the lowest coefficient of variation (17.3% in males). Weights of the reproductive organs showed the greatest variation with the highest coefficient of variation being that for the vesicular gland (77.7%). The liver, in both males (27.2%) and females (32.9%), was the most variable of the visceral organs studied. Relative increase in size of each variable for springhares (i.e., range of values) indicated a trend similar to that observed above for the overall coefficient of variation (Tables 13 & 14). External body length measurements showed only a 17% (male hind foot) to 45% (female body length) increase in size from the lower range value to that for the upper range. Length measurements on various parts of the reproductive tract, 92 9:. 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H 8.8 H 8.8 H 8.888 H 8.8 H 8.88 H 8.8 H 8.88 H 8.8 H 8.88 8881888 8H 8.H H 8.8 NH 8.88HH 8.888 8H N.8N H N.H8H NH 8.8HH 8.88 8H H.8 H 8.88 8881888 88 N.8 H 8.8 88. 8.88HH 8.888 88 8.NH H 8.88 88 8.8 H N.88 88 N.8 H 8.88 8881888 NN 8.H H H.8 HN 8.8HHH 8.888 NN 8.8H H N.H8 HN H.8 H H.88 HN 8.N H N.88 8881888 8N 8.8 H 8.8 8N N.88HH 8.888 8N N.8H H N.88 8N 8.8 H 8.N8 8N 8.8 H 8.H8 8881888 8H 8.8 H 8.8 8H 8.8NHH 8.HH8 8H 8.8H H N.88 8H 8.N H 8.H8 8H N.8 H 8.H8 8881888 NN 8.8 H 8.8 8N 8.88HH 8.N88 HN 8.8H H 8.88 HN H.8 H 8.88 HN N.8 H 8.88 8881888 8H 8.8 H 8.8 8H 8.88 H H.888 8H N.8H H N.8N 8H N.8 H N.88 8H 8.8 H 8.88 88N188N 8H 8.8 H N.8 8H H.88HH 8.888 8H 8.8 H 8.88 8H 8.N H N.88 8H 8.8 H 8.88 88N188N 8 8.8 H 8.8 8 N.N8 H N.8HN 8 8.NH H 8.H8 8 8.8 H 8.8N 8 8.8 H 8.8N 88H188H m..8.8 H H 888: m..8.8 H H 888: m..8.8 H H 888: m..8.8 H H 888: m..8.8 H H 888: H888 880v Luwcma mcwwm> Awe 8.8—me3 .8854 33 853883 8.8888: H888 888888 888H 8888 8888H8 888H8 88an 883 8:04 .H.8.88888 8H 8H888 .0888 «80380888 .nuzouw HHsm N00 um unwfiwa mama m0m 0m8un*« .:088m8um> mo 8cmHwawmou n .>.o« 98 8N8 8N8 H888 888H83 888H 88.8N 88.8N H80 .>.8 HH888>8 0.8H 1 0.8 0.0H 1 0.8 mwcmm mum 8.N 0.0 08m H.N 0.0 Hmuou 0cm cmma Hamum>o H 0.0 0.0H H 0.0 0.08 0001000 N 8.0 0.08 N N.8 0.08 0801000 0N 0.H 0.0 0N 0.~ 8.0 0001000 00 0.H H.0H m0 0.H 0.0 0801000 N8 8.H 8.8 N8 0.H H.0H 0081008 08 0.8 0.0 08 8.H 8.0 0881008 8N 0.H 0.0 8N N.N 8.8 0881088 80 N.N 0.0 Hm 8.H 0.0 0801000 mm 0.H 0.8 mm 0.8 0.0 00N100~ mm 8.H 0.0 Hm 0.8 0.0 08N100N OH m.H 8.0 08 N.H 8.0 0081008 m .8.8 H H 888: H8. 8.8 H H888: AEEV mum>o 8084 8550 mum>o unwwm Away unmfima mama .H.8.88888 8H 8H888 99 however, indicated a 171% (vagina) to 689% (left testis) increase in size. Body weight and the weights of visceral organs underwent a 197% (female body weight) to 646% (female liver weight) change. Reproductive organs exhibited a 74-(left testis) to 154-(vesicular gland) fold change in weight. The high coefficients of variation and increase in size of parts of the reproductive tracts, particularly in the male, clearly reflect a postponement of growth and then rapid enlargement subsequent to weaning. Growth Equations Correlation coefficients r for tail, ear and hind foot lengths in males and females (Tables 15 0 16) were the least satisfactory, reflecting the fact that 84% to 98% of the growth of these body parts was completed before animals were weaned and available to the collector. Less than 0.26% of the variation r2 in tail and ear lengths, and less than 0.04% of the variation in hind foot length was explained by variation in eye lens weight. Highest correlation coefficients were obtained for body parts which showed the most persistent growth subsequent to weaning; most noticeably female body weight (r . 0.88), male body weight (r - 0.86), and testis length (r - 0.88). More than 732 of the variationr2 of these three parameters was determined by variation in eye lens weight. Among the b coefficients the effect of sex was most noticeable for liver weight, indicating that the liver of the female springhare grew at a much greater rate, relative to eye lens weight, than did the liver of the male. All of the regression coefficients b (P“<0.03) and correlation co- efficients presented in Tables 15 and 16 were positive and significant 1130 Table 15. Coefficient constants a and b, and correlation coefficients r for the linear regression of several growth variables I on dried eye lens weight X (mg) of male and female springhares. Size of samples as in Tables 13 and 14. Dependent Intercept Slope constant Correlation Coefficient of variable Y‘ constant b“ 1.1 8.3. *** coefficient determination a r r Females Bind foot length (mm) 151.5 0.0073 3 0.0023 0.1882 0.0354 Right kidney weight (dg) 27.0 0.0593 t 0.0050 0.6884 0.4739 Left kidney weight (dg) 23.7 0.0730 t 0.0052 0.7554 0.5706 Right ovary length (mm) 5.5 0.0088 t 0.0010 0.4791 0.2296 Left ovary length (In) 5.2 0.0097 t 0.0009 0.5334 0.2845 21.212 Hind foot length (mm) 151.3 0.0108 1 0.0041 0.1575 0.0248 Seminal vesicle Vt. (d8) -39.6 0.2332 3 0.0240 0.7150 0.5112 *Y - a + b(X). See Methods Section for details. ** Probability is < 0.008 in all cases that the slope b is not significantly different from zero. *** 8.8. - standard error. 101 Table 16. Coefficient constants a, b and b , and correlation coefficients r for the quadratic regression of several growth variables I on dried eye lens weight X (mg) of male and female springhares. Size of samples as in Tables 13 and 14. Dependent Intercept Slope constant Slope constant Correlation Coefficient of variable Y‘ constant bl“ :_1 S.B.*** b2 i_l S.E. coefficient determigation a r r Females Body weight (3) -104.5 12.51 i 0.84 -0.0119 1 0.0011 0.8829 0.7796 Body length (mm) 511.6 1.34 i 0.19 -0.0014 1 0.0003 0.5794 0.3358 Tail length (mm) 288.2 0.67 i 0.09 -0.0008 1; 0.0001 0.5028 0.2528 Ear length (mm) 63.0 0.03 1 0.01 -0.0000 1 0.0000 0.4273 0.1826 Heart weight (dg) 17.8 0.30 1.0.07 -0.0003 :_0.0001 0.5498 0.3023 Liver weight (d8) -202.4 3.24 i 0.65 -0.0034 _t 0.0009 0.5525 0.3053 Vaginal length (mm) 11.4 0.23 i 0.33 -0.0002 1 0.0001 0.5716 0.3267 @131 Body weight (g) 46.1 11.89 i 0.80 -0.0116 3 0.0011 0.8569 0.7343 Body length (mm) 583.2 1.00 i 0.10 -0.0010 :_0.0001 0.7142 0.5100 Tail length (mm) 325.6 0.48 i 0.08 [-0.0005 3 0.0001 0.4517 0.2041 Ear length (mm) 63.0 0.04 :1; 0.01 -0.0000 1 0.0000 0.4101 0.1682 Heart weight (dg) -2.2 0.39 i 0.08 -0.0004 1 0.0001 0.6935 0.4809 Liver weight (dg) 38.7 1.68 1 0.45 -0.0015 1; 0.0006 0.5753 0.3310 Rt. kidney weight (dg) 11.0 0.16 1 0.04 -0.0001 3 0.0000 0.6749 0.4555 Left kidney weight (dg) 9.6 0.17 :1; 0.04 -0.0001 1- 0.0000 0.7128 0.5080 Rt. vad deferens (mm) -42.8 0.80 i 0.11 -0.0008 _+_ 0.0001 0.7708 0.5941 Left vas deferens (mm) -40.3 0.78 :_0.11 -0.0007 :_0.0002 0.7723 0.5964 Rt. testes -168.2 0.96 1 0.12 -0.0007 1; 0.0002 0.8370 0.7006 weight (dg) Left testes ~154.5 0.86 i'0.16 -0.0004 1’0.0002 0.8599 0.7394 weight (dg) Rt. testes -41.7 0.35 i 0.03 -0.0003 1 0.0000 0.8794 0.7734 length Gun) Left tastes -40.2 0.34 i 0.04 -0.0003 1 -.0001 0.8760 0.7673 length (mm) * Y - a + b1(X) + b2(X2). See Methods Section for details. “Probability that the slope b1 is not significantly differenct from zero <0.02 in all cases. ***Standard error. 102 (P<0.01). Instantaneous Growth Rates Since all parameters measured on springhares were fitted to eye lens weight, the shape of growth curves based upon mean values from Tables 13 and 14 were similar, not only for body (Figure 17) and testis length (Figure 18), but for all of the body parts measured. The primary differences among mean growth curves were in the timing of the transition from.linear to curvilinear growth, steepness, and flatness of the latter' part of the curve. Mean growth curves for the reproductive organs of males differed somewhat in that they showed curvilinear growth prior to linear growth, reflecting the fact that rapid growth of the reproductive tract of males did not commence until after weaning. Except for the organs of the reproductive tract of males, all body measurements taken showed instantaneous growth rate (velocity) curves similar to that for body length (Figure 17), again differing mostly in their steepness and in the eye lens weight at which they became curvili- near. Because of their late and very rapid growth, the testes and ves- icular glands yielded "bell-shaped" velocity curves (Figure 14). Patterns of Growth In females, the liver, ovary, heart, kidney, and body weights con- tinued to increase rapidly long after 95% of the potential body length was attained (Table 14, Figure 19). Males showed the same general growth characteristics, but to a lesser degree (Table 13). The testes were the last organs to undergo rapid growth. Once rapid growth of the testes com- menced, however, they showed the highest growth rate of any of the body parts studied. In males, the reproductive tract was the last part of the Figure 17. Figure 18. 103 Relationship in the male springhare of dried eye lens weight to mean length of the body (0) and growth rate of the body (A body length (mm)/A 50mg lens weight) (0). Trancepts represent one standard deviation. The growth rate curve is based upon a three point floating mean and was fitted by eye. Table 13 gives the size of the sample at each point. Relationship in the male springhare of dried eye lens weight to mean length of the right testis (0) and growth rate of the right testis (£3 testis length (mm)/ A 50mg lens weight). See Figure 17 for further details. Body length (mm) §§§§§§§§§§§ ‘ I T I - 104 O O 660_‘____._#__‘_7. - . i. I75 225 275 325 375 425 475 525 575 625 8 m N 80158113 r Testis length (mm) 883‘ I I v Eye lens weight (m9) Figure 17. |75 225 275 325 375 425 475 525 675 625 Eye lens weight (mg) Figure 18. I22 4 HA - l0.6 - 9.8 - 9.0 - 8.2 - 7.4 - 6.6 - 5.8 - 5.0 - 4.2 4 3.4 Growth rate (mm) Growth rate (mm) 105 100 98- V 90- 86- 82- 78- 74- 70- 66- 62- 58- 54- 46- A Heart weight A Body we‘ v 1119111111892; weight , -LN«1n‘ i V Right testis weight Percentage of full grown size 8883 20- 24- 13 let emergence from burrow I maturity -e Sexual ’ l l l L A I J l l 0175 225 27 525 375 425 475 525 575 625 675 Eye lens weight (mg) Figure 19. Size of several body parts of the female springhare relative to dried eye lens weight from 150 to 650mg. Changes in testis weight are also shown. See text for details. 106 body to reach full-grown size. There was a definite gradient from external parts (i.e., hind foot and ear lengths) to internal organs (especially testis length) as far as attainment of full-grown size was concerned (Figure 19). At weaning (175mg lens weight), when springhares began life above ground, body (44%), eye lens (26%), and testis (3%) weights were still far below those of full-grown individuals and exhibited linear growth for a considerable time after weaning. Body (82%), tail (84%), ear (93%), and hind feet (98%) lengths were close to full-grown size and already showed curvi- linear growth. Fleagle and Samonds (1975) suggested that the differences in the growth schedule of various body parts may be important in determining which parts are affected by growth disturbances, namely, malnutrition or illness. This may also apply to springhares but, in addition, the growth schedule of this species further suggests that the individual is being structured to effectively detect and avoid the many predators in its environment (Sections One and Three) at the time it first leaves the burrow. The distribution of eye lens weights suggests that the age distri- bution was much the same for both male and female springhares (Tables 13 8 14, Section Three). Upon this basis it seems justifiable to use the overall mean value of each body part for determining the occurrence and extent of sexual dimorphism (Table 17). The five external measurements of springhares did not reveal any statistically significant sexual dimorphism (Table 17). The overall mean weight of the liver of females was 80g more than that of males. This difference was highly significant. (z- 4.890, 1r<0.0005). Foetal weight was not correlated with liver weight in those 107 .u0008v enema uenu 808880e0ou0ee :o8un8>uv unmanaume :86 8... 8.N ~.o 1~ H 9... .8 H a... 08.0 59.3 5.26 Sod .3... _.~ 8... 8.: 1+. “.3 «.3 H 8.88 0.5 59.3 39.3. 888... N86 85 a... 92 .8 8.; 8.8.. 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N.N 86 and H 38 888 .+1 28 A90 232. .26.. names :8 enema 88 .0.0 8.H e.0.m 8.H «azuHHAnAonm 0588;18 oueouawu80 N mucououu80 seas «Hosea some 08a: 080w8um> .88 new 88n080eh :8 ea aoHnamm no ou8m .nounsme8uem uo manna 8000 m=o8ua> you e0588> :mea ounHomnn 0088 00081008a usw8u 0cm oHneUHIoHaI uo noa8umaaoo .88 oHnna 108 females with an eye lens weight greater than 400mg (r - 0.07, d.f. = 93, P > 0.2). There was, however, a significant difference in mean liver weight between pregnant (57g) and non-pregnant (52g) adult females with an eye lens weight of more than 400mg (Z = 1.90, P > 0.03). Increase in liver weight with pregnancy has also been reported in both the albino rat Rattus norvegicus (MacKay 1928) and the howler monkey A. caraya (Malinow at al. 1966). Lawes and Gilbert (1859) found that the liver increased in relative size as the physical condition of animals improved. This also appeared to be the case with springhares as both the physical condition of the pregnant springhare (Section Seven), and the weight of the liver in- creased during gestation. The mean value for the right kidney of females was significantly greater than for the males (Table 17). The difference between the mean lengths of the hind feet of males and females was almost significant (P 8 0.06), as was the difference between mean weights of the left and right kidneys of males (P‘<0.07). The mean body weights of males and females provided in Table 17 include the weight of the foetuses and stomach contents. Upon subtracting these weights, the mean body weight of the females became 2.68kg and that of the male became 2.67kg. -Relative Orgggiweighg There was little, if any, difference in weights of kidneys, heart, and liver, relative to body weight, between newly weaned male and female springhares (200-249mg lens weight) and fully-grown individuals (550—599mg lens weight) (Table 18). This was in contrast to the vesicu— lar gland and testis, both of which underwent a 24-fold increase in 109 1 1 1 08.8 08.0 08.0 08.0 0001000 08030m 1 1 1 80.8 08.0 08.0 88.0 0081008 080800 1 1 1 80.8 88.0 08.0 08.0 08N100H 080808 80.0 08.0 88.0 00.8 88.0 08.0 08.0 0001000 080: 08.0 08.0 08.0 80.8 88.0 08.0 88.0 0881008 0802 No.0 «0.0 80.0 80.8 88.0 08.0 08.0 08N1008 0802 8.80 8 £0 CC 85 3 83 383 2.30 0.0 00 8:30. 02.3.. 95 £30.. 0008 0:080 00Hao8m0> 00>88 0000: 0008 0nw8m 0:08 000 K00 0008M . .88 0:0 88 008009 :8 00 0080 1500 no 0080 .0aw803 0:08 080 00800 00 0080000000 000000080 00050 000 80:0803 0000 0008\050803 00000 00 050803 8000 Mo 0000000000 0 00 0000000x0 00005008000 080500 000 080B 00 0050803 00000 .08 08009 110 relative weight as springhares attained full size. Comparisons of the relative mean organ weights of adult spring- hares and ten other similar-sized mammalian species belonging to four different Orders (Crile & Quiring 1940) indicate (Table 19) that the mean relative weight of kidneys, heart and liver in adult male and fe- male springhares are lower than for any of the other species, except for the heart weight of the brown howler monkey Alouatta palliata. Qggan Weight Allometric Equations Kidney, heart and liver weights, as predicted by the general mam? malian organ weight allometric formulas for mammals (Brody 1945), were calculated for male and female springhares in the SOD—549mg eye lens weight category (Table 20). In all six comparisons the observed organ weight was only 50% to 63% of the predicted general organ weight for mammals. The data (Tables 19 & 20) show that the kidney, heart, and liver weights of springhares were atypically low for mature mammals of this body size. This may be related in some way to the body form, bi- pedal-saltatory locomotion, and/or arid environment of the springhare. Predictive allometric size equations for various body parts of juvenile and adult male and female springhares (Table 21) were good pre- dictors of size in all cases except for testis and vesicular gland weight. That the weights of the testis and vesicular gland were not adequately described by a single allometric equation is undoubtedly due to the de- layed and then sudden and rapid growth of these two organs subsequent to weaning. Separate allometric equations for different periods of growth are probably necessary to adequately describe the change in size of these two organs in juvenile and adult springhares. Based upon its allometric equation (Table 21), each body part can 11]. Table 19. Comparisons of relative kidney, heart, and liver weights of adult springhares and ten other mammalian species of similar body weight. Siipieg#_75ean body Kidneys Heart Liver Species* Sex size weight(kg) (combined wt.) weight weight n (I) (Z) (Z) Pedetes capensis M 53 3.07 0.364 0.353 1.550 Pedetes oapensis P 35 3.18 0.359 0.286 1.082 (springhare) Erithiaon dorsatum M 1 3.41 1.114 0.455 3.167 Erithizon dorsatum F 1 2.80 0.963 0.700 4.000 (porcupine) Dasyprocta puntctata M6? 2 3.17 0.485 0.553 2.681 (brown agouti) Guniculus paca M6F 3 3.63 0.625 0.444 5.152 (spotted agouti) Lepus oapensis F 1 2.93 0.416 1.024 1.772 (African hare) Lepus arcticus 1.90 0.964 1.094 2.470 chus arcticus F 2.64 1.015 1.497 3.479 (Artic hare) Felis dbmesticus 3.78 1.177 0.445 3.354 Felts damesticus F 2.88 0.765 0.429 3.212 (domestic cat) Octocyon megaZotis F 1 3.34 0.955 0.738 3.743 (bat-cared fox) Aloutta palliata M&F 6 3.12 0.684 0.250 3.783 (brown howler monkey) Ckrcopithecus aethiops M 4 3.96 0.380 0.809 2.179 (vervet monkey) Cbbus capucinus M6? 14 3.10 0.461 0.600 -- (white-faced monkey) *Except for springhares all values taken from Crile 6 Quiring (1940). 112 000003 00>00 No.0 8.00 00.0 0.0 000003 00000 and 0.: 0.0: 032008 0000000 8000 800 003 £00 03 003 £00 03 0800080 33 £005 003 £0003 00>00000 00>00000 000000000 000000000 00000 000<200 .A0800 >0o0mv 0000000 00 0000000 0cm 000000o0 00000Eo000 000003 0000c 000 0000 00>0000 0003 00000> 0>0000000m .000003 0000 000 00 >0o00000 000801000 000 00 00000000000 000000 000 0000 000 0000003 00000& 000 .00>00 .0000: 00>000no 000 000000000 .00 0000s 113 Table 21. Allometric equations of the form Y - axb where X is the body weight (kg). Equations predict the length or weight of various body parts 1' of juvenile and adult springhares (150-600 mg lens weight). Equations were derived from the mean values for each 5003 category of eye lens weight as presented in Tables 13 and 14. Initial growth Allometric Correlation Dependent variable Sex constant constant coefficient Growth*** Y a b 1 15.8.* r P“ Body length (cm) M 62.8 0.25 i 0.01 0.99 <0.001 - F 62.0 0.42 i 0.01 0.98 <0.001 - Tail length (cm) M 34.2 0.22 i 0.02 0.94 <0.01 - F 34.9 0.18 i 0.02 0.88 <0.05 - Hind foot (cm) M 15.2 0.02 i 0.01 0.36 >0.50 - Ear length (cm) M 6.6 0.08 i 0.01 0.82 <0.05 - F 6.5 0.09 1 0.01 0.91 <0.05 - Right kidney (dg) M 21.1 0.84 i 0.02 0.99 <0.001 - P 17.9 1.00 i 0.05 0.98 <0.001 0 Left kidney (dg) M 20.9 0.89 1 0.02 0.99 <0.001 - F 17.6 1.04 i 0.05 0.98 <0.001 0 Heart weight (dg) M 32.9 1.01 i 0.06 0.97 <0.01 0 F 38.4 0.79 i 0.03 0.99 <0.001 - Liver weight (dg) M 171.0 0.92 i 0.05 0.98 <0.001 0 1" 132.8 1.28 i 0.04 0.99 <0.001 + Right vas deferens (m) M 39.4 1.24 1 0.06 0.98 <0.001 + Left vas deferens (mm) M 36.4 1.34 i 0.08 0.98 <0.001 4- Right vesicular gland (m)M 0.03 6.83 i- 0.32 0.98 <0.001 + Right testis weight (dg) M 0.08 6.60 i 0.40 0.97 <0.01 + Left testis weight (dg) M 0.1 6.30 i 0.41 0.97 <0.01 + Right testis length (m) M 4.0 2.32 i 0.17 0.96 <0.01 + Left testis length (m) M 3.9 2.38 _+_- 0.16 0.96 <0.01 + Vagina length (m) P 3.0 0.68 _+_ 0.03 0.99 <0.001 - Right ovary length (m) I" 4.8 0.61 1 0.06 0.94 <0.01 - *One standard error. **Probability that the correlation coefficient is not significantly different from zero. ***(0) - organ grows at the same rate as the body, i.¢. the allometric constant is not significantly different from 1.0, (+) - the rate of growth of the organ is significantly greater than that of the body, (-) - the rate of growth of the organ is significantly less than that of the body. 114 be placed into one of three growth-pattern classes: External Linear - body, tail, hind feet and ear length, -low allometric constant (0.02‘100 Primates“ 116.? 6.3 0.87 i 0.014 0.95 - 268 Heart weight (g) Springhares M 3.63 0.92 1; 0.06 0.49 0 87 F 3.83 0.76 i 0.05 0.43 - 127 Mammals 1151' 5.8 0.98 _+_; 0.01 0.99 - >100 Primates M5? 5.2 0.97 t 0.02 0.99 0 321 Liver weight (g) Springhare M 11.65 1.28 _t 0.06 0.50 + 87 F 10.65 1.43 i 0.05 0.51 + 123 Manuals M&F 33.3 0.87 _+_- 0.01 0.99 - >100 Primates 1181‘ 32.2 0.93 i 0.02 0.98 - 293 *From Brody (1945), for mice to steers or larger mammals. **From Stahl (1965), based on primates from tree shrews to gorillas. ***As for Table 21. 116 of the allometric constants b and the level of significance of the cor- relation coefficients r provide some indication of the significance of the difference between allometric constants b. Heart weight and kidney weight allometric constants b were significantly higher in male than in female springhares (P~ ‘c’ .3, 20 .E x O 3 8 |3I8232833384348535863687378+ Number of Physuloptero copsnsis Figure 21. 80 F . 70- 60- 5° ' Y¥=O.I56X¥-30.25 (r-O.9|4,df:8.P<0.00I) o 40- 3 3°" (r=O.889,df-8,P<0.00I) 20 IO JAAAIJ 1 44_L 1 44411 14441144, I50 200 250 300 350 400 450 500 550 600 650 Lens weight (mg) Figure 22. 125 Frequency Distribution The frequency distribution of Pt capensis in adult springhares (Figure 21) indicated a strong positive skewness, i.e., low numbers of nematodes were found most frequently. Dispersion and skewness of the frequency distribution in adult springhares were similar in both sexes. Juveniles yielded a frequency distribution which was similar to that of adults but more strongly skewed to the left as 90% of the females and 85% of the males showed no worms. The frequency distribution of P. capensis in adult springhares was significantly different from Poisson distribution (IL 550mg), males had a lower incidence of infection (48%) than females (75%). This difference 126 was not significant (x2 = 3.49, d.f. = l, P > 0.06) however. Commencing at a lens weight of approximately 250mg, the likelihood than an individual would exhibit infection by P. capensis increased with age (Figure 22). The association of eye lens weight with incidence yielded significant positive correlation coefficients both in males and in females (Figure 22). The regression equations describing these two relationships did not differ significantly (F - 1.03, d.f. - 16, P > 0.30). Effect of host reproductive status. The overall percentages of male and female springhares parasitized with P. capensis were identical (34%) (Table 23). Frequency of infection did not differ significantly between juvenile males (17.4%) and females (9.1%) (x2 - 1.56, d.f. = l, P > 0.020) nor between adult males (33.8%) and females (43.2%) (x2 = 0.14, d.f. = l, P > 0.50). The highest incidence of parasitism was among lactating females (54%). This value was not significantly different, however, from that for non-lactating adult females (412) (x2 . 1.38, d.f. - 1, P > 0.20). Neither did P. capensis parasitize pregnant adult females (47%) more frequently than non-pregnant adult females (35%) (x2 - 2.78, d.f. - l, P > 0.09). The incidence of worms among pregnant females was indepen- dent of foetal age (r = 0.265, d.f. - 6, P > 0.25), foetal weight (r = 0.659, d.f. - 4, P > 0.25), and trimester of gestation (x2 - 3.83, d.f. - 2, P > 0.15). Intensity of Infection Effect of host4§g_. The overall intensity of P. capensis was 8.3 per springhare (Table 23). Adult infection (11.0 worms) was signifi- cantly greater than for juveniles (1.7 worms) (Z - 8.95, P‘<0.001). In males, juveniles showed 2.3 nematodes against 6.8 for adults (Z - 2.52, 127 .uOuuo cumucuum e 2 H son a S n.« H «.5 .3 H «a 9: 8«.o com .8232... «2 2 H .3 m «« «.« H «.8 «.c .+. o.: 93 8«.o 8.. 31.... «2 e« H «3 a a in H a... a... H «J «.3 «21. .5 8:82; «3 R H as e e «.:H O: me .+. n.o« 1% 82. 8 .323 . muuusuosa 8 H e; « e 02..“ 03 as H1: «in 87° 3 2:23 usssnownusoz : H «S e «_ n; H «.2 o." H .3: «.3 ST». «2 8:38 segue: .«« H use a 2 _.n H 1: c.« H 4.: .2: 87¢ a: 818C «2 e« H 2: a 2 mé H can «.« H 12 «.3 SI. 8« aaaafiu 3:3 on M com o o e.n .+.. 1: o... H e; 1e 3 .e 2 32.3 «:52... o« H «3 _ « «.« .+. «g: o; H «A 92 87° :3 and... «2 e« H a? o e _.« H «.2 a; H as «.3 87¢ 8« .32. i=3 «n .+. «3 _ _ m.« H «.2 e; .+. n.« i: «21. S «was. 322.3 .m.m _ H mayo: mayo: .m.m _.H e.m.m _.H ARV Aasuosv a Awwv announce oo_ A now: an A so“: use: wouomucu umoz use: =o«uoou:« onus sauna somEOum use: ammo: .oz sumo: .02 no; mayo: use mesa: wouoousn mo mason Ounsom m>wuusvoumo¢ .ocouuacuuow uou uxou mom .co>«w Oman one mucoucoo monsoon are «0 uswaoz as: some are use asuos co—A can OnA nauseous: oouozwcuuam uo women: .souosw:«uam no mango o>quoswouoou some :« wmczmmuu damumoNuomxm uo auumsoucu was sucovuocu .mN sunny 128 P“<0.006). In females, juveniles yielded 1.0 worms compared with 15.1 for adults (Z = 5.06, P‘<0.00l). There were positive significant relationships between intensity of infestation and lens weight (relative age) for both male and female springhares (Figure 23). The two regression equations describing these relationships (Figure 23) were significantly different (5" 24.3, d.f. = 16, ZI<0.001), suggesting that females, as they became older, tended to support increasingly greater worm burdens than males. This sex disparity in nematode numbers became evident at about the time of sexual maturity. Effect of host rgproductive status. A sex difference existed be- tween the intensity of P5 capensis in male (5.3 worms) and in female (11.4 worms) springhares (Z - 2.74,1":0.003) (Table 23). Burdens were not significantly different between juvenile male (2.3 worms) and juve- nile female (1.0 worms) springhares (Z1. 0.843, 19> 0.20), but did differ significantly between adult males (6.8 worms) and adult females (15.1 worms) (Z - 2.83, P< 0.002). This sex difference was due primarily to eight adult females with superinfections of more than 100 nematodes. No adult males had more than 100 nematodes. Lactating females showed the highest nematode burdens (20.3 worms). Intensity of infection in lactating females was significantly greater than in non-lactating females (10.4 worms) (2 - 1.69, P<-0.05). This difference was largely due to the fact that the two springhares with highest worm burdens (275 and 280 worms) were both lactating. The intensity of nematodes in pregnant females (14.4 worms) was not significantly different from that for non-pregnant adult females (17.1 worms) (Z - 0.405, P > 0.50). The intensity of infection among pregnant females was not related Figure 23. Figure 24. 129 Regression of intensity of Physaloptera capensis on dried eye lens weight (relative age) of springhares. Each point represents the mean intensity of worms among male (0) and female (0) springhares occurring within a 50mg category of eye lens weight. n=560. Regression of incidence of Physaloptera capensis on intensity in springhares. Each point represents incidence and mean intensity values of worms among male (0) and female (0) springhares occurring within a 50mg category of eye lens weight. n=560. Nmnber of nematodes Spnnghores with nematodes (9E) 32 28 24 20 130 Y2 ' 0.074Xg- I755 *- (r80.950,df'8.P <0.00” '6 'OOIQXQ '252 s s < (r O.Tl3,df 8.? 0,03), ”’ ’ O 1 L l I 70 60 ISO 200 250 300 350 400 450 500 550 SW 650 Lens weight (mg) Figure 23. / / / v, -4.346x,+io.os // (possum. / " P<0.00I)/ o / / o // O o// (r-o.895.d1-s.r 0.25) or foetal weight (r I 0.056, d.f. I 24, P > 0.50). Relationship Between Incidence and Intensity of Infection Menthly samples indicated positive highly significant correlations between incidence and intensity of infestations of both male (p I 0.602, d.f. I 21, P< 0.005) and female (r I 0.751, d.f. I 22, P'<0.0005) springhares. Similarly, positive and highly significant correlation coefficients were detected both in male and female springhares (Figure 24) when incidence was paired with intensity of infection at each of ten 50mg categories of eye lens weight (relative age). The lepes of the re— sultant two regression equations (Figure 24) were significantly different (23 - 2.524, d.f. -= 16, P<0.03). Effect of Host Food Intake and Diet 0n the Kalahari Study Area, springhares foraged almost entirely on roots, corms, stems, and leaves of grasses from the time this study com- menced in August until December 1971. They gradually changed to grass seeds from December through May 1972, switched back again to other grass parts from July through January 1973, and switched once again to seeds from.March through May 1973. March was the month of peak seed consump- tion in both 1972 and 1973. At this time stomachs contained little ma- terial other than grass seeds. Springhares also foraged on seeds in the Eastern Study Area but to a lesser extent. The relative amounts of forage consumed by springhares of different reproductive status (Table 23) were obtained by comparing mean wet weights of stomach contents. Stomach content weights were not signifi- cantly different between juvenile males (46.2g) and juvenile females (50.0g) (Z I 0.805, P > 0.14). Significant differences between mean wet 132 weights of stomach contents were found between males (53.7g) and females (65.83) (Z I 4.283, P‘<0.00003), juvenile and adult males (55.9g) (Z I 2.104, P<=0.02), juvenile and adult females (70.9g) (Z I 3.990, P1<0.0003), adult males and adult females (Z I 3.528, P1<0.001), and lactating (82.1g) and non-lactating females (66.2g) (Z I 2.123, P<=0.02). A significant correlation did not exist between wet weight of the stomach contents and eye lens weight (relative age) among male spring- hares (r I 0.044, d.f. I 251, P > 0.07). Females, in contrast, showed a highly significant positive correlation between these variables (r I 0.286, d.f. I 265, P<=0.005). Effect of Host Physical Condition Kidney fat index was independent of incidence of infection in each of the five reproductive classes (Table 24) (x2 < 6.61, d.f. I 3, P > 0.08), and when all springhares were considered together regardless of reproductive class (x2 - 2.89, d.f. - 3, P > 0.30). Springhares with an "excellent" kidney fat index harbored 14.6 nematodes as opposed to 6.0 nematodes in springhares with a lesser kidney fat index but this difference was not significant (Z I 1.342, P > 0.17). Kidney fat index (r'<0.l49, P > 0.15) and condition index (r‘< 0.139, P > 0.12) were independent of intensity of infection within each repro- ductive class (Table 24). Kidney fat (r - 0.076, d.f. - 377, P > 0.07) and condition indexes (r I 0.048, d.f. I 545, P > 0.12) were independent of nematode burdens when all springhares were considered together. Three of the four springhares with the heaviest nematode burdens (161-280 worms) had excellent kidney fat ratings. Female springhares underwent fat deposition and depletion cycles which correspond closely with the reproductive cycle; fat reserves 1333 .sousswsuunoxnlhos no wanna: see: as .uluos so“: nousnwswuno uo owsusouuom e ¢.~ an ~mn c.- as nc_ a.m~ on «N n.c o— _n ~.m e. an w.o an _q— cool so memos «.9 aN mm ~.n_ oo o— m.¢ n— o ~.o «a a— ~.q s— an n.a an «N anemone usu aose«a on A_v 0.9 au ~n— c.m— 04 mm a.@ on o _.o m m— o.o c. —~ ~.e an an acosoua new hosed: osoeawv m.q mm om o.c dc mm m.n mm o ~.o m~ n~ o.o o n 6.5 on we own an wovcsouuss soacax Ame o.q_ an no m.~_ _q on ~.wc «N s o.c o ~ n.- «c m m.e mm m~ usu an wougsmso aoce«a Ase huge «use some: auan coco sumo: >uuo ooco goo: xuus ooco sumo: amen ooco sumo; «exude assess sumo: some“ inseam ivfiocu .oz icoucu nausea .oz isoucu iuwocu .oz icoucu ivuosu .oz isousu ivuosm .oz icuusu ivuocu .oz sou amass: memos mogmsou moamsou agave moaosou o~uco>=n memos ouqco>sn moans u~3v< cacao no «nook ucssmoum occcwouoicoz o>uuosvouno¢ :Ouuumsou douumazn van msumum m>uuo=vouauu uncuum> «o .nso«u«:«uov you uses «on .Ausu assomxv moumnmswnem wcoso smorumuu sameneNummxm mo haunsoucu use oosokucu .cw ounce 134 increased throughout the gestation period, were highest at parturition and decreased with lactation. There were no data to indicate that the intensity of P. capensis infection was significantly related to this "fat cycle". Effect of Host Density and Habitat Incidence and intensity of infestation within a habitat indicate the relative suitability of that habitat for fostering a particular host- parasite relationship. The Kalahari and Eastern Study Areas were divided into seven habitat types on the basis of vegetation structure, soil type, and forage utilization by herbivores (Table 25). Incidence and intensity of P. capensis infestations in 333 adult springhares collected within these habitats were analyzed in respect to percentage bare ground, grass canopy, woody canopy and relative springhare population density as mea- sured by the mean numbers of fecal pellets per mil-acre plot. Significant negative relationships (Table 25) were found between both incidence and intensity of P. capensis infections and percentage bare ground. In addition, positive, significant associations were indi- cated (Table 25) for both incidence and intensity of parasitism and per- centage grass canopy. WOody canopy and density of the springhare popula- tion were not significantly correlated (Table 25) with either incidence or intensity of infection. Incidence and intensity values for P. capensis on the four undis- turbed habitats in the Kalahari Study Area (Figures 4a, b) were combined as were the values for the three degraded habitats located in the Eastern Study Area (Figures 4c, d). The incidence of infestation was significant- ly higher (62%) in the Kalahari than in the Eastern Study Area (22%) (x2 I 51.98, d.f. I 1, P<=0.001). The intensity of infestation also was 1135 ca~.oA om~.ca nmo.ov o~o.cv i 1 i i auunuasnoua ~«c.o- «e«.o cn«.c «e«.oi . i i . os«s> a Nu«msuucu oe_.os an«.oa noo.ov noo.ov . i 7 i . scaawasacaa mn.o- n«.o _a.c _a.oi . i i . oa~s> a oosovuoeu m.o c a as o.o o c« a Ana assuage esc«vcoa mono snowmen e.o n. m as o.c a« c«_ «_ Ana oaau«ae unsavool sumo sasswuuosomuo: _.on o o oo_ o.o o n_ _ Ace asam«ae soumussw souonmb Aeoasecsmaev acessuom snouoam «.m c «a me «.«~ an as n Asa osau«mv mesa use: n.e c an em c.a me _n n Ase asau«me was: uswu n.c a_ _m «a n.c so «« ma Ace «sesame assss>su use: n.o «_ «s cm a.m« as n. as Asa ussw«ae smcsw>su umwm Avonusunuussv assesses uo~a use >aoceo xeocou wcsouw use: use ANV sumo: nouszmcuuno successes mumuuom Assam woo: N macaw N mums N @5903 venomucu no .02 we .oz usuanuz .mcoauwcuuow ecu axou mum .nnn I onus museum .msuos mo auumcoucu use oocovuosu was nuouoadusa gauges: usow mo some cassava couuuuuomso we cosmos one museums“ mouuwuunoAOHQ adore use a suconouuuooo couusaouuoo .zoso Esau wouuoHHOU soussmsquau :« mmmswmsu usuumoNummxm no Auumsousu was masseuse“ may use common use use newest ousuwnaz «nonwnuunu so>wn no nodunuuouon .nN smash Springhares with Nematodes (7.) Number of Nematodes Figure 25. 136 ‘21) —- ‘flfl " . l6- be 1 I I I | 24- ° ‘ ‘\ “ I I I I 4o~ 36- b 32— ear 24- 20— IS- 12- s- ,9] ¥ \ I97I I972 I973 Month Incidence (a) and mean intensity (b) of Physalcpterl Rapensis in male (O--—O) and female (O--C) , springhares during each of 25 consecutive months. n=560. 137 significantly higher in the Kalahari (12.0 worms) than in the Eastern Study Area (7.1 worms) (Z I 2.334, P<=0.01). Data for the two savannah habitats (Figure 4a) in the Kalahari Study Area were combined as were the data for the two pan habitats (Fi- gure 4b). Springhares collected in savannah and pan habitats did not differ either in incidence (x2 I 2.98, d.f. I l, P > 0.08) or intensity (Z I 0.420, P > 0.30) of P. capensis infestation. All twelve of the pans sampled yielded infected springhares. Based upon the fecal pellet densities of springhares, the C. dactylon Habitat (Figure 4d), with its loose sandy soil and relatively sparse grass cover, provided ecological conditions most favorable to the maintenance of high springhare numbers. Nevertheless, P. capensis was absent in springhares from this habitat in spite of its presence in the adjacent Metsemotlahaba Open Woodland Habitat (Figure 4c). In the East and West Savannah Habitats, where springhare densities were less than 2% that of the C. dactylon Habitat, 66% of the springhares were infected and the intensity of infection was 13.7 worms. The minimal population density of springhares necessary to main- tain P. capensis is not known but is below that required to maintain a mean 0.4 fecal pellets per mil-acre. Seasonal Variation in Incidence and Intensity of Infection Bimonthly samples. An annual pattern in either intensity or inci- dence of Ph capensis infestations in springhares was not apparent when data were plotted on a monthly basis (Figures 25a & b). The seasonal environment in which this interaction occurred, however, warranted a more detailed examination of the data. Therefore, the data base was lumped into bimonthly samples to increase sample size and to extend the time 138 span represented by each sample (Table 26). Bimonthly incidence of P. capensis was not significantly related to rainfall, temperature, day length, or protein in either male or female springhares (r-<0.482, d.f. I 9, P > 0.15) No significant correlations were observed between intensity of in- fection in male springhares and bimonthly rainfall, temperature, protein or day length (r‘<0.488, d.f. I 9, P’> 0.07). Bimonthly intensity of infection in female springhares, however, was significantly related to rainfall (I'I 0.572, d.f. I 9,F"< 0.04) and temperature (r I 0.563, d.f. I 9, ZW<0.04) although not to day length or protein (r< 0.446, d.f. I 9, P > 0.08). Combined bimonthly samples. Bimonthly samples from each of the two years covered by this study were combined (Figure 26) so that all data fell into one of six bimonthly samples ("combined bimonthly" samples). Combined bimonthly incidence of infection was not significantly correlated with rainfall, temperature, day length nor with protein in either sex of springhares (I“<0.482, d.f. I 4, 5’> 0.17). Although the intensity of infection in male springhares increased in combined bimonthly samples from 4.0 worms in August-September to 5.6 worms in December-January (Figure 26a), this difference was not signifi- cant (Z I 1.062, I’> 0.14). In females, however, the intensity of in- fection did increase significantly from 7.6 worms in June-July to 14.3 worms in December-January (Z I 0.925, I"=0.04) (Figure 26a). Combined bimonthly intensity of infection in males was significant- ly correlated with rainfall (I’I 0.886, d.f. I 4, 1*<0.01), temperature (r- 0.726, d.f. I 4, P< 0.05), protein (1». 0.801, d.f. I 4, .P<0.03) and day length (III 0.791, d.f. I 4, I*=0.05) (Figures 26a, b, c). 139 Table 26. Bimonthly incidence and intensity of Physaloptera capsnsis in male and female springhares. physical condition indexes of the host are also provided. Values for several environmental parameters and See text for definitions. Oct Dec Feb Apr Jun Aug Oct Dec Feb Apr Jun Total Variable Nov Jan Mar May Jul Sep Nov Jan Mar May Jul or means Sample size of males 16 17 17 23 18 32 22 31 29 35 37 277 Sample size of females 15 19 16 19 28 23 33 24 31 31 28 267 Incidence in males (2) 44 41 59 17 44 28 18 29 41 33 44 36.0 Incidence ' in females(Z) 53 47 56 21 18 25 52 36 26 39 25 36.2 Intensity in males 9.2 5.6 4.5 0.5 2.6 2.6 1.4 5.7 6.0 8.8 6.8 4.8 Intensity in females 16.8 25.0 22.4 7.2 5.1 19.6 8.6 3.6 2.3 12.5 10.1 12.1 Total rain- fall (mm) 123.8 154.2 58.2 9.7 0.1 8.2 19.5 41.4 51.3 31.9 0.0 45.3 Mean temper- ature (0°) 23.8 25.1 24.0 17.2 12.0 17.6 23.8 25.1 24.0 17.0 12.0 20.2 Stomach protein (2) 13.5 14.5 13.7 14.0 11.0 10.4 15.1 18.3 16.2 17.2 12.9 14.3 Midmonth day length (h) 13.0 13.4 12.3 11.0 10.4 11.3 13.0 13.4 12.3 11.0 10.4 12.0 Male condi- tion index 4.14 4.14 4.48 4.09 4.09 4.04 3.90 3.95 3.92 3.95 4.04 4.06 Female condi- tion index 3.91 3.96 4.04 3.83 3.83 3.80 3.70 3.51 3.40 3.70 3.78 3.77 Male kidney fat index - - - - 1.60 1.88 1.87 2.27 2.33 2.23 2.49 2.10 Female kidney - fat index - - - - 2.83 3.00 2.73 2.42 2.36 2.39 2.71 2.63 140 IGr- O (I) § I4- 312- 2 s '0'- 2 e— E 5 6" -o- 4 ’30- ‘°“~o---o 3‘ 8 2 2 E 0 O. S p. ’8 .a 5 s s = 5 a s E 3 >5 8 Aug Oct Dec Feb A Jun Sep Nov Jan Mar Mg; Jul Month Figure 26. Relationship between time of year and combined bimonthly values for (a) mean intensity of Physaloptera capensfs in male (O---O) and female'(O—‘—O)'springhares, (b) rain- fall ((?---0) and temperature (H), and (c) springhare stomach protein (O---O) and day length (O--O). n=560. See text for definitions. . 141 Combined bimonthly samples in females showed highly significant correla- tion between nematode numbers and rainfall (r I 0.928, d.f. I 4, P’< 0.005), temperature (r I 0.969, d.f. I 4, P<=0.002), and day length (r I 0.965, d.f. I 4, P”<0.005), while correlation with protein remained insignificant (r I 0.571, d.f. I 4, P > 0.12) (Figures 26a, b, c). Effect on host physical condition. Monthly condition index was not significantly related to intensity of nematode infections in male spring- hares (r I 0.222, d.f. I 21, P > 0.15) but there was a significant posiI tive correlation in females (r I 0.374, d.f. I 22, I”<0.04). Condition index was not significantly correlated with bimonthly intensity of P. capensis in male springhares (r I 0.039, d.f. I 9, P > 0.30) but a highly significant positive relationship existed for females (r I 0.845, d.f. I 9, P< 0.0005) (Table 26). Monthly intensity of P. capensis was not significantly correlated with kidney fat index in either male (r I 0.048, d.f. I 11, P> 0.40) or female springhares (r I 0.088, d.f. I 11, P’> 0.40). However, bi- monthly kidney fat index showed significant positive association with burdens of P. capensis in both male (I'I 0.827, d.f. I 4, I’<0.02) and female (1" 0.757, d.f. I 4, 1’<0.04) springhares (Table 26). DISCUSSION Frequency Distribution The distributions of P. capensis ova, and of intermediate and definitive hosts, were probably important variables in determining the incidence and intensity of infections in springhares. The negative bi- nomial distribution exhibited by P5 capensis in springhares indicates that springhares were being unequally exposed to infestation. Either 142 there was individual variation in host susceptibility and resistance to infestation and/or a non-random dispersal of infective larvae in the environment. Relationship Between Incidence and Intensity As pointed out by Williams and Harris (1965), the association be- tween intensity and incidence of infection by helminths has not received much attention. This study, and the results of Hu (1931), Bertram (1949) and wynne Owen and Pemberton (1962), suggest that incidence of infection may be directly associated with intensity of infection. That this is not invariably the case, however, was shown by Lewis (1968). Host Resistance Development of an immune response by springhares to P. capensis infection was not directly examined. Good evidence, however, against the presence of a significant and durable immunity, according to Thomas (1958), Weinmann (1966), Dunsmore and Dudzinski (1968) and Lewis and Twigg (1972), is the increase in both incidence and intensity of infest- ation with age. This was the pattern of infestation in springhares. The apparent absence of immunological reaction in springhares is not surprising. Parasites, such as P. capensis, which do not penetrate or feed on host tissue but remain within the lumen of the gastrointest- inal tract are, in a sense, outside the body of the host (Cameron 1956). Since such parasites have little direct contact with host tissue they probably initiate little or no serological reaction in the host (Culbert- son 1941; Beer 1952; Soulsby 1958; Lees 1962; Mykytowycz 1964; Thomas 1965; Weinmann 1966). 143 Host Susceptibility Effect of hostgggg. The incidence and intensity of P. capensis rose progressively with the age of springhares. A similar pattern be- tween host age and infestation has been reported in numerous other host- parasite interactions (Thomas 1958, 1965; Bull 1964; Anderson & Beaudoin 1966; Lewis 1963; Kisielewska 1971; Amin 1975; Farhang-Azad 1977; Kennedy 1977). Beer (1952), Thomas (1964) and Amin (1975) postulated that parasites in the gut are limited to some extent by the size of the gut; older (larger) host presenting more surface area, space and food to accommodate higher worm burdens. This might account in part for the increased worm intensity with age of springhares but it can be of only minor importance as much of the stomach space in the population of springhares was not being used; 65% of the springhares had no worms and only 4% had more than 50 worms. The most likely explanation for the positive relationship between infestation and the age of the host is a lack of exposure to infection among pre-weaned springhares and increased duration of exposure with age. The absence of significant difference in the levels of infestation between juvenile male and female springhares was not surprising. Haley (1958), Dudzinski and Mykytowycz (1963), Thomas (1964), Fischer and Freeman (1969) and Bach, Johnson and Coggins (1975) also failed to find a host sexrinfluence on the abundance of parasites until sexual maturity was attained. The increase in infection with P. capensis associated with the sexual maturity of springhares indicates that physiological and/or be- havioral changes associated with attainment of sexual maturity may in- fluence this host-parasite system. 144 Effect of host reproductive status. Incidence of infection was independent of sex of the host while intensity of infection was signifi- cantly higher in female springhares. There is considerable literature indicating that the sex of the host often influences the host-parasite interaction (Addis 1946; Todd & Hollingworth 1952; Each 1967; Each, Johnson & Coggins 1975). It is unclear in most cases, however, whether the predisposing elements influencing such relationships depend upon sex-differences in host survival, stress, physiology, biochemistry, beha- vior, intake of larvae, or a combination of these. The sex ratio in springhares was at parity in foetuses, juveniles and adults (Section Three). This suggests that the mortality rate was the same for male and female springhares within all age classes and that, on the average, females did not live longer than males. Thus, sex-related differences in longevity or exposure time to infection cannot account for the higher burdens of P. capensis exhibited by female springhares. There is some indirect evidence (Butynski 1975) that male and female springhares did not differ in the sites they grazed or in spatial activity. Thus, these behaviors were probably unimportant in explaining the dispar- ity of worm loads between sexes. Male springhares did not undergo noticeable cyclical changes in testicular and seminiferous tubule size (Section Five). In contrast, fe- males underwent a reproductive cycle (Section Three) which was recurrent throughout the year and which involved pregnancy and lactation as the two primary phases. As part of the reproductive cycle of female spring- hares there were predictable changes in sex hormone levels, food intake, and physical condition. Many workers have suggested that sex—linked differences in suscept- ibility to parasitization are influenced by host hormones, particularly 145 the sex hormones (Campbell & Melcher 1940; Haley 1958; Bull 1959; Mathies 1959; Dobson 1961a, b, 1964; Smyth 1962; Dunsmore 1966a; Lewis & Twigg 1972). There are two reasons why it is unlikely that sex hormones were responsible for the sex difference in burdens of P. capensis among springhares. First, a parasite located in the anterior gastrointestinal tract and not in direct contact with host tissue probably has little, and perhaps no, opportunity to ingest host hormones. Second, evidence from the literature (Dobson 1961a, b; Lees 1962; Thomas 1964, 1975; Dunsmore & Dudzinski 1968) indicates that, in vertebrates, female harmones usually reduce susceptibility of the host to parasitism whereas it is the male hormones which generally increase susceptibility. Data were presented which showed that (i) adult springhares ate more forage than juveniles; (ii) adult females ate more food than adult males; (iii) females consumed increasingly more forage as they became older; and (iv) lactating females ingested more food than non-lactating adult females. Since greater forage consumption generally results in a higher intake of namatode larvae (Duke 1933; Thomas 1958, 1965; Schad 1962; Mykytowycz 1964; LaPage 1968; Lewis 1968; Hine 8 Kennedy 1974; Amin 1975; Each, Johnson & Coggins 1975) disparities in the rate of food intake probably account for some of the difference in P. capensis infections among spring- hares. There is no doubt (Gordon 1948; Christian 1950; Selye 1950; Sheppe & Adams 1957; Nobel 1961; Layne 1963; Mykytowycz 1964; Weinmann & Rothman 1967; Jackson & Farmer 1970; Myers et a2. 1971, Each, Gibbons & Bourque 1975) that stress in the host can reduce the resistance and increase the susceptibility of the host to parasitism. Perhaps the most commonly cited source of stress associated with increased infection by nematodes is the loss of physical condition (Fraser and Robertson 1933; Clunies Ross 1935; 146 Taylor 1938; Whitlock 1949; Mergan, Parnell & Rayski 1950; Hunter 1953; Paver, Parnell & Morgan 1955; Vegors at al. 1955; Gordon 1958; Brunsdon 1964; Thomas 1964; Read 1970; Ciordia at al. 1971; Lincoln & Anderson 1973; Michel 1974), frequently allied with the high nutritional demands of lactation (Stoll 1940; Bull 1964; Spedding, Brown & Large 1964; Connan 1968, 1971a, b; Brunsdon & Vlassoff 1971). Female springhares had large fat deposits at the time of parturition. The nutrional drain of lactation, however, was considerable. Although adult female springhares showed a 24% higher food intake during lactation than during gestation, most or all fat reserves were depleted before the neonate was weaned. After weaning, body-fat accumulation resumed in the adult female and continued until the next parturition. Cyclic changes in physical condition associated with the reproductive cycle was a source of stress to which female, but not male, springhares were subjected. This added stress may have accounted for part of the higher burden of P. capensis in adult females, particularly those in lactation. It is not clear (O'Sullivan & Donald 1970; Michel 1974) whether the often witnessed increase in burdens of nematodes in hosts which are lac- tating and/or in reduced physical condition is the result of delayed loss of already established worms or of an increased rate of establishment of new worms. Increased forage (£.e., larvae) intake by springhares losing condition suggests that, in this case, an increase in the establishment of new worms was at least partially responsible for the higher parasite loads. 147 Effect of Physaloptera capensis on the Host Effect on host fertilipy. Adverse effects of a parasite on its host are often first recognizable as a reduction in host physical condi- tion and fertility. The possibility, however, that high infestations of parasites are a result, rather than a cause, of poor physical condition must also be considered (Elton 1942; Christian 1950; Wynne-Edwards 1962). Incidence and intensity of infection did not differ significantly between pregnant and non-pregnant adult female springhares. The high overall percentage (76%) of adult females which were pregnant (Section Three) suggests that fertility was near maximum throughout the two year collection period. There is no evidence that the fertility of spring- hares was affected by densities of P. capensis. Effect on host physical condition. Physical condition was apparently unaffected by numbers of P. capensis. The incidence of infection was independent of kidney fat index, and the intensity of infection was not significantly related to either kidney fat index or condition index. Neither were significant correlations observed between monthly intensities of P. capensis and the kidney fat index of male or female springhares or the condition index of males. Significant positive relationships were found between burdens of P. capensis and the monthly and bimonthly condition indexes of females or the bimonthly kidney fat index of males and females. These correlations may not, however, indicate a cause-effect relationship between the condi- tion of springhares and numbers of P. capensis. They probably reflect, instead, their common association with several seasonal environment vari- ables which favored both the deposition of body fat and the establishment of P. capensis. 148 Pathology. The evidence given above indicates that P. capensis is a benign parasite of springhares. Lincoln and Anderson (1973) ob- served a similar relationship between P. maxillaris and the skunk Mephitis mephitis. In contrast, several species of physalopterines have been associated with various degrees of pathology in the definitive host (Yokoyawa 1922; Seurat 1937; Schell 1952; Soulsby 1968; Schmidt & Roberts 1977), in some cases leading to chronic debiliatation (Krupp 1962; Feldman at al. 1972; Nettles, Prestwood & Davidson 1975) and even death (Ehlers 1931; Mannig 1938; Gier & Ameel 1959; Tacal & Corpuz 1962). Effect of the External Environment As noted earlier, the life cycle of P. capensis is not completely known and neither are the physical tolerances and requirements of its ova, larvae, and intermediate hosts. Nevertheless, the close similarity of the life cycles of the five species of PhysaZoptera which have been studied suggest that inference of the basic physalopterine life cycle to P. cap- ensis is justified. Likewise, the literature (Boughton 1932, 1937; Lucker 1941; Gordon 1958; Levine 1963, 1968; Rogers & Sommerville 1963; Rates 1965; Dunsmore 1966b; Michel 1969; Ollerenshaw & Smith 1969; Each, Hazen & Aho 1977) indicates that there is a basic set of physical factors in the external environment which determine the longevity and success of free-living stages of terrestrial helminths. The model in Figure 27 indicates what are probably the most impor- tant variables and interactions determining successful transmission of parasitic terrestrial nematode ova and larvae. This model can be used as an aid in attempts to distinguish and elucidate those environmental fac- tors most variable among habitats and thus most likely to be responsible for differences among habitats in the transmission of nematodes. 149 .mpwcmo: com axon 0mm .mouncwvcw me: on: meowuomumucw LocwE can gametes: .mzcwut ocean use as wouszuwmow can meowuc_:aom wwwxmatt camaitwtuzq; 2w meocououuw: unuwnocIcooBLLL new ucwuczcecm cw ucmuaomsw umcE on so msw:o:u meowuemuouzn .mm>uc_ 1:: s>c outlast: _cwammoaaou uwuwmsbum mo :cwmmwamcmpu can Hm>w>azm seceEQCFs>ot wcwuusmu: acoECCLH>ce Hmzwmuxo m:u we moaacwum> .NN musmwh r mozoto>o=oE=o2ooE L a c2863.: _Ee_om_ 9.228th— \ \\ e//« 38: I ‘ cozofiom 7.24.6.2 7:323th . 223.502.. 332.3 o:oE__ooco=2 map—.04“. >m<2En «333031 mobs. anzooum , 5:23; map—.04.... wkdz .xoca 72:2 d 26 3225: .o 5.3.522. a 3.593. 52.52263 150 The model is used here to compare the C. dactylon Habitat, where P. capensis was not present in springhares, with the East and West Savannah Habitats (jointly referred to here as the Savannah Habitat), where P. capensis was common. Soil, herbivores, and macroclimate were important in determining the type, amount, and persistence of the vegetation (Figure 27). The vegetation, in turn, influenced the production and survival of inter- mediate hosts, the amount of soil turnover, and the microclimatic vari- ables of temperature, moisture, and radiation. Soil and the macroclimate variables of temperature, precipitation, and solar radiation (Figure 27) did not differ appreciably between the two habitats. Herbivore biomass, and thus grass utilization, however, were much higher in the C. dactylon Habitat, where populations of sheep, cattle, goats, and springhares were present, than in the Savannah Habitat where springhares and antelopes occurred. In the C. dactylon Habitat one grass species, Gynodon dactylon, accounted for more than 97% of the grass cover. The aerial portions of this rhizomatous grass were complete- ly removed by livestock and springhares. This left the habitat, which had a 44% grass canopy during the wet season, devoid of grass canOpy for approximately seven months of the year. During this period springhares turned over nearly all of the soil in the habitat down to a depth of four to six inches in search of C. ddctylon rhizomes. In contrast, the Savan- nah Habitat supported several common grass species (Butynski 1975), the 41% grass canopy during the wet season was only reduced to 33% during the dry season, and little soil disturbance occurred. The higher utilization of vegetation and greater turnover of soil found on the C. dactylon Hab- itat probably subjected any P. capensis ova occurring there to consider- ably more irradiation, dessication, and burial, and fewer intermediate 151 hosts, than ova on the Savannah Habitat. The significant negative relationships between infection of P. capensis in springhares and the percentage bare ground (Table 25), and the significant positive relation- ships between infection and grass canopy, probably reflect the indirect influence of soil turnover and vegetation on the viability and trans- mission of ova and larvae. Moisture is almost certainly the proximate factor most seriously affecting infestation of nematodes under arid conditions. It appears that the species composition, biomass, and persistence of the grass vegetation is the most important indirect variable accounting for the differences observed in number of P. capensis between habitats. The overriding im- portance of vegetation and moisture to the transmission of helminths, especially in areas of highly seasonal rainfall, has also been suggested by Edwards and Wilson (1958), Dinnik and Dinnik (1961), Durie (1961), Levine (1963), Bull (1964), Thomas (1965), Dunsmore (1966b), and Olleren- shaw and Smith (1969). Seasonal Variation in Intensity of Infection The intensity of an infestation is governed by rates of parasite recruitment and loss (Thomas 1965). It is likely that the rate of P. capensis loss from the springhare stomach was more or less constant throughout the year. Stressors associated with springhares which might influence the survival of parasites, including immunological defense mechanisms, hormone levels, reproductive effort, plan of nutrition, and physical condition, as discussed earlier, appeared either to be absent, constant, or not to reach levels likely to affect P. capensis mortality. If the mortality rate of P- capensis within springhare stomachs did not vary with time of year, then the increase in intensity of P. capensis 152 burdens during the wet summer season must be attributable to seasonal differences in the availability of infective larvae. In Botswana, climatic and environmental conditions are most favor- able for development and survival of nematode ova, larvae and intermediate hosts during the wet summer months when frosts are absent, solar radia- tion is relatively low, and soil and air moisture are relatively high. Utilization of different foraging areas and foods during the year accounts for seasonal changes in the intensity of some parasite infections (Conner 1953; Gerking 1962; Lees 1962; Esch, Hazon & Aho 1977). Indi- rect evidence indicates that springhares do not alter the size or loca- tion of feeding areas during the year (Butynski 1975). Springhares do, however, switch from a diet rich in grass seeds during the wet season to one comprised of other grass parts during the remainder of the year. This seasonal alteration in diet may influence exposure to infected in- termediate hosts. Host Density-Dependent Hypothesis According to Dunsmore (1972) it is "...regarded as axiomatic that an increase in host density will be followed by an increase in numbers of parasites...But the evidence in support of this is not conclusive." This "host-density hypothesis" suggests that the environmental conditions pre- sent during increasingly higher densities of the host favor increased infestation and/or establishment of the parasite. Some workers have shown that the density of the host may indeed be associated with an increase in parasitism (Dunsmore 1972; Esch, Gibbons 8 Bourque 1975). This, however, is not invariably the case. The present study, and the observations of Elton et a2. (1931), Rausch and Tiner (1948, 1949), Layne (1963, 1968), Spedding, Brown 8 Large (1964), McManus 153 and Arnold (1965), Anderson and Beaudoin (1966), Southcott, Langlands & Heath (1970), and Tenora and Zejda (1974) indicate that the rate of para- sitism is frequently independent of the density of the host. Some para- site-host systems even exhibit an inverse relationship between host and parasite densities (Wilson 1945; weeker 1962; Cameron & Gibbs 1966; Tenora & Zejda 1974). One difficulty with the host-density hypothesis is that it ignores the possibility that external environmental conditions favoring a high host density may be detrimental to the parasite. Habitats most condu— cive to high densities of springhares have loose, sandy, well-drained soils, sparsely vegetated feeding and burrowing areas, high surface temI peratures, and a long dry season (Butynski 1975). Under these circum- stances, losses to dessication, heat, irradiation, and burial of ova, lar- vae, and intermediate hosts are probably high. There may be such a strong inverse relationship between the density of hosts and the availability of parasite infective stages that the number of parasites becoming es- tablished in the host does not rise with an increase in the density of the host regardless of the degree to which changes in resistance and susceptibility of the host favor the parasite. A second shortcoming of the host-density hypothesis is also appa- rent. In a well-balanced host-parasite interaction, where the parasite is benign and the host does not mount significant resistance against the parasite, conditions detrimental to the host may also be unfavorable for establishment and/or maintenance of the parasite. In the P. capensis- springhare relationship, this is indicated by the positive correlation between the physical condition of springhares and number of nematodes. Southcott, Langlands & Heath (1970) failed to find a positive 154 relationship between the density of sheep and number of parasites, not only because of the loss of ova and larvae to drought, but also because "...sheep grazed at high stocking rates selected a diet containing fewer larvae per unit dry matter than was available on the pasture." "Para- site avoidance" behavior on the part of the host may thus also occur as changes in the densities of hosts and parasites occur. In summary, the host density-department hypothesis appears to be based upon at least three wrong assumptions: (i) that infective larvae are always present to infect hosts exhibiting low resistance and/or high susceptibility, (ii) that there is always a positive relationship between the density of the host and the suitability of the internal environment of the host for the parasite, and (iii) that hosts do not exhibit "para- site avoidance" behavior. Thus, the situation arises, apparently fre- quently and possibly in several ways, where conditions conducive to a high density of the host are those which are unfavorable to certain pha- ses of the parasite' life cycle. Regulation of Physaloptera capensis Pppulations Bradleyfs Hypotheses. Bradley (1972, 1974) hypothesized that there are three ways by which populations of parasites are regulated: (Hypo- thesis I) by transmission of the parasite, since small changes in the rate of transmission can lead to large changes in the population size of the parasite; (Hypothesis II) at the population level of the host by immuno- logical and pathological processes involving either the death of the most heavily infected hosts or an immune response which leaves the host both parasite-free and immune, and (Hypothesis III) at the individual host level by premunition and other partial immune processes. Unlike Hypotheses II and III, Hypothesis I is independent of host 155 density. Bradley's (1972, 1975) hypotheses are based solely on negative feedback from extrinsic sources in the environment. He does not propose that some populations of parasites are self-regulating through intrinsic mechanisms (wynne-Edwards 1965; Chitty 1967; Pimental 1968; McLaren 1971). .Rggulation by the host population (Hypothesis II). The physical condition and fertility of springhares were unrelated to burdens of P. capensis. This, and the apparent absence of pathology among the most hea- vily infected individuals indicates that numbers of P. capensis were not controlled by the death of the most heavily infected hosts. Increase in both incidence and intensity of P. capensis with in- creasing age of springhares is strong evidence against the occurrence of an important age resistance or an immune response in which all P. capen- sis are destroyed and springhares left immune. Hypothesis 11 seems not to apply to P. capensis in the springhare. .Rggplation by the host individual (Hypothesis III);, Because of its location in the stomach and apparently low association with the tis- sues of the host, it is unlikely that P. capensis initiates a significant immune response from springhares or that premunition occurs. This is supported by evidence for a positive relationship between parasite density and host age. Hypothesis III appears not to apply to P. capensis in springhares. Transmission-regulated infection (Hypothesis 1). One school of demography (Uvarov 1931; Andrewartha & Birch 1954; Nfrgaard 1956; Birch 1957; Reynoldson 1957; Hutchinson 1961) suggests that some populations, especially those of small organisms in harsh environments, are largely controlled by density-independent factors and persist indefinitely in the absence of density-dependent mechanisms. 156 P. capensis ova and larvae qualify as small organisms in a harsh environment. The generally unfavorable physical conditions of the spring- hare's external environment for transmission of nematode ova, larvae, and intermediate hosts, and deductions from the literature concerning the regulation of populations, particularly nematode populations (Huffaker 1958; Rates 1965; Esch 1977), suggest that P. capensis populations are governed largely by density-independent mechanisms (Hypothesis I) and that density-dependent factors are operating and important at all popu- lation densities but are obscured by dominant density-independent factors. SUMMARY The ecology of the springhare Pedetes capensis was studied in the Republic of Botswana (August 1971 - August 1974). A mean 24.2 i 1.6 springhares were collected monthly from September 1971 through July 1973. Data on 560 juveniles and adults, and 153 foetuses were analyzed. Data on the following aspects of springhare ecology are provided; burrow struc- ture and fossorial ecology; pelage and molt; reproductive ecology; repro- duction in the male; growth and development of the foetus; body and organ growth of juveniles and adults; and host and ecological association of the nematode Physaloptera capensis. Springhare burrows were located on well-drained sandy soils, and were generally associated with an abundant short-grass food resources and flat open terrain. The composition of grasses in the vicinity of the burrows differed markedly from that of the surrounding areas as a result of spring- hare activities. Digging behavior is discussed. Excavation of burrows occurred during all times of the year, but was most frequent during the wet season. The overall pattern of three excavated burrows was circular with most entrances on the periphery of the system; mean depth - 78cm, mean length - 41.1m, greatest depth - 122cm, tunnel height - 17-25cm, tunnel width - 10-23cm, and mean number of entrances - 9.3. Both temporary and permanent earthen plugs were formed within the burrows. No chambers, side-pockets, blind tunnels, food or nesting materials were found in the burrow. Two types of entrances, "mound" and "clean" holes, were present. Springhares are not colonial. One springhare, or at most a mother 157 158 with its one young, was associated with each burrow. Burrows provide microenvironments favorable for conservation or water and energy. They also provide protection from predation and weather. Pelages of juvenile and adult springhares are described. Molt pattern is of the caudad type in both juvenile and adult molts. In a sample of 326 springhares, 64% of the juveniles and 19% of the adults were in molt. Smallest springhares in juvenile molt weighed 1.7kg. Time of juvenile molt was associated with body size and age. Incidence of juvenile molt was highest during the wet season, but this molt occurred in all months. The first adult molt usually commenced when body weight was 2.7kg to 2.9 kg. Peak months for the annual adult molt were December and January. No springhares were in adult molt during July and August. The adult molt oc- curred when environmental conditions seemed to be most favorable. Juvenile and adult molts showed significant positive correlations with monthly total rainfall, mean air temperature, and mean forage protein. There was also a significant positive relationship between adult molt and day length at mid-month. No sexual dimorphism was found for pelage, molt pattern, or timing of the molt. Lactation appeared to hinder molt. Seventy-six percent of adult female springhares were pregnant. Mean interval between conceptions was estimated at 101 days, mean interval bet- ween parturition and conception was approximately 24 days. Springhares were typically monotocous. Twinning occurred in less than 1% of the pregnancies. There was no difference between the number of implantations in each uterine horn. Neonates were confined to the burrow and totally dependent upon the mother until they attained a body weight of approximately 1.3kg. 159 Lactating females were observed during all times of the year. Seven- ty—nine percent of non-pregnant adult females were lactating, 46% were lactating, 31% were simultaneously pregnant and lactating, and only 4% were neither pregnant nor lactating. The mean period of lactation was estimated at 46 days. Among all springhares collected the juvenile to adult ratio was 28:72 in females, 29:71 in males, and 28:72 overall. The male to female ratio was 51:49 in foetuses, 51:49 in juveniles, 50:50 in adults, and 51:49 overall. Pregnant springhares were found during each of 24 consecutive months. The reproductive effort of the species was unusally constant throughout the year. The possible reproductive strategy of the springhare is consid- ered. Data from 153 embryoes and foetuses of the springhare were used to describe prenatal growth and development. Body measurements and equations describing the rate of growth relative to body weight are provided for body, forehead—rump, ear, hind foot, and tail lengths. Changes in the external morphology of the foetus, relative to body weight and approximate age, are also described. Both the absolute birth weight (252g) and the birth weight relative to the weight of the mother (8.3%) were consider- ably lower than predicted for a mammal of this body size. Growth of the reproductive tract of male springhares is described relative to dried eye lens weight. Seventy-two percent of the 284 males collected exhibited spermatogenesis. A testis weight of 2.3g, dried baculum weight of 41mg and seminiferous tubule diameter of 117nm can be used with a high degree of confidence for separating prepubertal and post- pubertal male springhares. 160 Fecundity in males, expressed as testis weight and seminiferous tubule diameter, was not associated with monthly total rainfall, mean air tempera- ture, or day length at mid-month. Seasonal atrophy or senescence of the reproductive tract did not occur. The reproductive effort of both male and female springhares appeared to be constant throughout the year. Absolute measurements are given for 29 body parts in male and female springhares. Linear and quadratic equations are presented describing the growth rates of body parts relative to dried eye lens weight. Allometric equations, based on body weight, are used for intra— and interspecific com- parisons of the relative growth rates of various body parts. Appendage length measurements were much less variable than either the length or weight measurements of the organs. A gradient from external ap- pendages to internal organs existed for the attainment of full adult size. No sexual dimorphism was apparent among body weight, hind foot length, tail length, ear length, and overall body length. Liver and right kidney weights were significantly greater in females than in males. Pregnant females had significantly heavier livers than did non-pregnant adult females. There was little change in relative weight of the kidneys, heart and liver from the time of weaning until full adult size was attained. Kidney, heart, and liver weights were atypically low for mam- mals of this body size. Based upon their allometric equations, each body part measured could be classified as having one of three distinct growth patterns. Allometric constants for male and female heart and kidney weights were similar to those of other mature mammals while those for liver weight were considerably higher. Incidence and intensity of the stomach nematode, PhysaZoptera capensis, in relation to the age, sex, reproductive status, physical condition, den» sity and habitat of its host, the springhare, were investigated. There was 161 no evidence for an immunological response in springhares against Physa- Zoptera capensis. All data indicated that this nematode is a benign para— site of the springhare. The frequency distribution of Physaloptera cap- ensis appeared to be best represented by a negative binomial model, indi— cating that infections were not randomly distributed within the springhare population. Thirty-four percent of all springhares were parasitized by Physalop— tera capensis and the mean number of worms per host was 8.3. Both the incidence and intensity of infection were lower in juveniles (14.2% and 1.7 worms) than in adults (42.5% and 11.0 worms). There was no intersex- ual difference in incidence but males had a lower nematode burden (5.3 worms) than females (11.4 worms). Lactating females had a greater worm burden (20.3 worms) than non-lactating adult females (10.4 worms). Incidence and intensity of infection showed a positive association with the amount of grass cover in the host habitat but were independent of host density and host physical condition. Intensity, but not incidence, of parasitism showed significant positive correlations with monthly total rainfall, mean temperature, day length at middmonth, host physical condi- tion, and mean protein level of the host stomach contents. Both the incidence and the intensity of Physaboptera capensis in springhares were probably determined by rates of food intake and by densi- ties of infective larvae on the foraging area. Age and reproductive state of the springhare host were important modifiers of larvae intake, whereas densities of infective larvae on the foraging area were probably largely determined by weather and vegetative factors. Possible explanations for the absence of a positive association between springhare density and nematode burden are provided. It is hypothesized that Physalqptena capensis populations are governed mainly by density-independent factors. RECOMMENDATIONS Data collected on several other aspects of the ecology of the springhare will be presented elsewhere. Tentative titles for these papers are: (i) Reproductive activity of the female springhare, (ii) Frequency distribution of Physaloptera capensis‘ in the springhare, (iii) Variation in physical condition of the springhare, (iv) Variation in the nutrient intake of the springhare, and (v) Habitat selection in the springhare and two Lepus spp. The present data base on the ecology of the springhare would bene- fit most from future research directed towards establishing (i) the re- liability of present estimates of the springhare gestation period, (ii) the age of springhares relative to eye lens weight, and (iii) the life cycle of Physaloptera capensis. 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