I 71-23,229 REILLY, Raymond E . , 1928FACTORS INFLUENCING HABITAT SELECTION BY THE LEAST CHIPMUNK IN UPPER MICHIGAN. Michigan State University, Ph.D., 1971 Ecology U niversity Microfilms, A XEROX C om pany , A nn A rbor, M ichigan FACTORS INFLUENCING HABITAT SELECTION BY THE LEAST CHIPMUNK IN UPPER MICHIGAN By Raymond E. Reilly A Thesis Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Fisheries and Wildlife 1970 ABSTRACT Habitat selection by the least chipmunk (Eutamius minimus) in Upper Michigan was evaluated by field observation and experimental tests of visual factors. Each of four, 5-acre experimental areas was subdivided into approximately 250 sq. ft. units and analysed in detail in the field for the habitat factors: brushpile and woody ground cover distribution and density, distribution and degree of horizontal visibility, density of overhead cover and light intensity. These habitat characteristics were ranked on a three point scale system. Habitats with good horizontal visibility, medium to dense brush piles and open canopies with correspondingly higher light intensities were occupied significantly more than other habitats. The extent of low, woody ground vegetation appeared to have no significance. Eleven chipmunks were tested in an enclosure 10 ft. in diameter for their preference of: restricted vertical and horizontal visibility and two different perch heights. Pens restricting horizontal visibility were used significantly less than pens with unrestricted^vision, unless the pens had high perches in them, which were used more than pens with low perches. Restricted vertical visibility was not a significant factor. I conclude that habitats selected for good horizontal visibility and high brush pile density provided protective cover as well as the opportunity for visual social communication and spacing of the population. Certain types of vocalizations were also noted. ACKNOWLEDGEMENTS I wish to thank Dr. Leslie Gysel, Professor of Wildlife Management, for his technical advice during the course of this study. I also wish to thank Drs. Bollin Baker, John King, John Cantlon and Stephenson for serving on my graduate committee. I am indebted to the many people who assisted me with the design of the miniature transmitter, especially Harold Meirs, Michigan Bell Telephone, Harvey Ball, U. S. Corps of Engineers, and William Cochran, Illinois Natural History Survey. I am also grateful to lake Superior State College and the Michigan! State University Agricultural Experiment Station for some financial assistance. Special thanks are necessary for Dr. David Behmer, Lake Superior State College, for his invaluable advice concerning the statistical analysis of the data. I wish to recognize the efforts of Steven and Brian Reilly who spent many hours assisting me in the field. project would not have been possible. ii Without their aid this TABLE OF CONTENTS Page INTRODUCTION................................................. 1 Review of the pro b l e m ................................. The species habitat .................................... 1 *+ FIELD STUDIES .............................................. 7 Introduction............................................ Description and location of area ....... 7 7 MATERIALS AND METHODS............................. ........ 23 Trapping ........................ Habitat analysis........................................ Age and sex criteria.................................... Population estimates.................................... Home range estimates........................ Telemetry............................................... Vocalizations........................................... 23 26 30 32 32 33 36 RESULTS...................................................... 38 Home range determinations............................... Seasonal behavior of habitat selection.................. Animal density and distribution......................... Statistical analysis.................................... Vocalizations........................................... 38 *fl ^3 **6 30 PEN EXPERIMENT .............................................. 58 Introduction............................................ 58 MATERIALS AND METHODS ....................................... 58 Apparatus......................................... Experimental design................... 58 6l RESULTS...................................................... 63 Pen utilization......................................... Perch utilization....................................... 63 68 iii Page DISCUSSION AND CONCLUSIONS................................... ?1 LITERATURE CITED............................................. 77 APPENDIX...................................................... 85 iv LIST OF TABLES Table Page 1. A summary of tree densities for each Area's forest types.. 10 2. Quantitative description of the study Areas: size, number of habitat units, number of trap .................................. sites and spacing. 28 3. Criteria used for habitat analysis............ 31 k. Summary of home range data for males.................... 39 5. Summary of home range data for females.............. 40 6. Trapping effort and success for Area I.........*........ ^2 7> Estimated chipmunk density............ *................ ^ 8. Estimated chipmunk use of the different areas in acres and percentage................................. ^5 Percentage of habitat units in each category for habitat factors occurring within the estimated home ranges for all areas............................... ^7 Percentage composition of the habitat units in each category for each area's habitat factors............ ^8 11. Summary of Chi Square values ......... ^9 12. Results of statistical treatment of experimental data using the F test................................... 6*t Analysis of interaction data for the main effect-horizontal treatment............................. 65 Analysis of interaction data for the main effect-vertical treatment............................... 66 Analysis of interaction data for the main effect-perch height..................................... 67 A summary of perch use data............................. 69 9. 10. 13lb. 15. 16. v LIST OF FIGURES Figure Page 1. Cover map of Area 1 ...................................... 9 2. Cover map of Area II..................................... 11 3. Cover map of Area III.................................... 13 h. Cover map of Area IV..................................... 14 3* Cover map of Area V ...................................... 22 6. Illustration of the method used to evaluate the horizontal visibility of habitat units............... 29 7. Graphic relationship of chipmunk "quip" calls and season......................................... 31 8. Diagram of enclosure..................................... 39 vi LIST OF PLATKS Page Plate I Figure 1. North corner of Area.....I ...................... 16 Figure 2. North central portion of Area 1 ................. 16 Plate II Figure 3. South central portion of Area II................ 17 Figure 4. South east portion of Area II.................... 17 Figure 3* North west portion of Area III.................. 18 Figure 6. South central portion of Area III................ l8 Figure 7. Central portion alongtrial, Area IV............. 19 Figure 8. South west portion of Area IV................... 19 Plate III Plate IV Plate V Figure 9. Figure 10. Looking west from northeast corner of Area V 20 Looking south from northeast corner of Area V.... 20 A trial trapping location having a high density of chipmunks............................... 21 Plate VI Figure 11. Plate VII Figure 12. The live trap used............................. vii Page Plate VIII Figure 15. Transmitter, uncoated and coated with denture material. .... 35 Experimental enclosure......................... 60 Plate IX Figure 14. viii INTRODUCTION Many authors have noted that animals are not distributed at random but are found in certain habitats more frequently than in others. Some investigators have correlated animal density and distribution, with vegetational types (Dice, 1931; Grange, 19^8; Leopold, 19**8). Applied ecologists have attempted to create an optimal stage of vegetational succession for the management of squirrels (Allen, 19**3); grouse (Ammann, 1957); hares (Grange, 19**9) and other game animals. The interrelationship between the physical factors of the environment and habitat selection by mammals have been considered experimentally by a few early workers. Chenoweth (1917) attempted to relate mammal distributioi in a habitat to the evaporation quality of the air. Moody (1929) and Kalabukhow (1938) studied the influence of light intensity. More recent­ ly, Chew (1951) worked with the significance of water in the environment. Pruitt, (1953 and 1959) found a correlation between the moisture in the soil, physiological water loss (of the short-tail shrew (Blarina brevicauda, and its distribution in various soil and plant types. Hardy (19**5) noted that the soil texture and structure may affect burrowing species from dig­ ging their ground burrows. The significance of environmental temperatures has been examined experimentally by Stinson and Fisher (1953) and more recently by Ogilvie and Stinson (1966). The latter workers correlated the spatial distribution of the white-footed mouse (Peromyscus leucopus) deer mouse (P. maniculatus) and the house mouse (Mus musculus) to micro­ temperature variations within their environments. 1 Banasiak (196*0, 2 Behrend (1966) and Verme (1968) have attempted to explain the selection by white-tailed deer (Odocoileus virginiana) of certain conifer woodlands during the winter season based on the degree of physical comfort afford­ ed by their habitat. Another facet which has been reported to influence the selection of habitat is competitive exclusion. Odum (1959) states that where there is competition between ecologically similar species, the range of habitat conditions which each of the species occupies becomes restricted to the optimum. An illustration of this point can be taken from those periods when a species is more abundant and widely distributed and is inhabiting a portion of the habitat whose quality would be less that optimum. This implies (Evans, 19*+2) that an animal's occurrence may reflect habitat occupation rather than habitat selection. Whitaker (1 9 6 7 ) and Sheppe ( 1 9 6 7 ) described coactian effects between Peromyscus leucopus and Mus museulus. Whitaker implied that the latter species would inhabit the environment in which he found the former except for competitive exclusion. Sheppard ( 1 9 6 5 ) describes a similar coaction phenomenon between Eutamias amoenus and E. minimus. Sheppe*s work (1 9 6 7 ) with Peromyscus demonstrated that P. maniculatus was being excluded from a habitat by P. oreas. Calhoun (1 9 6 3 ) described the dominance relationship between Clethrionomys and Peromyscus. He suggested expansion of the home range of Peromyscus was inhibited by the presence of Clethrionomys; whose presence was communicated through vocal behavior. Walker's (196*0 experiments with 3 genera of woodland mice, utilized soil-vegetation units from two forest types translocated to the lab. He concluded that Clethrionomys and Napeozapus tended to choose the unite in which they reach their greatest abundance. Tevis (1956) has considered the effects of ground vegetation on habitat selection by certain rodents. Lack (19^9) stated that a bird's selection of its habitat is accom­ plished by utilizing environmental recognition features which are not necessarily those directly essential to their existence. He classified the important environmental "cues" as proximate as opposed to ultimate; the former serving as "guidelines" which will orient the animal to a habitat which should provide the physiologically important necessities for survival. He believed that the choice of the ultimate factors are innate and set through natural selection. Tinbergen (19^8) suggested that the habitat recognition "mechanism" or releaser mechanism involves the individual's response to the "sum effect" of several different stimuli in the environment. Once the total stimuli from a number of factors reaches a particular threshold level peculiar to the individual's habitat recog­ nition, then selection is possible. Wecker (1963) tested the influence of learning on habitat selection. Using the field subspecies of Peromyscus maniculatus. he concluded that both heredity and experience can play a role in determining the preference of P.m. bairdi for the field. Few studies have been conducted to evaluate what these important cues are for an animal's selection of habitat. Harris (1952) conducted an experiment designed to uncover selection cues important to two races of Peromyscus maniculatus. The precise characteristics of the objects were not ascertained in these experiments, but his results indicated that visual cues were important. Inheritance of the behavior of habitat selection has also been inves­ tigated by Klopfer (1965)* Sheppard et al. (1968), and discussed by Thorpe (19*+5) * Howard (1965)* Mayr (1963)» King (196?), and others. This idea is more understandable if one remembers that the animals are polygenic for many characteristics, including behavior, many of which have not yet been defined. Thorpe (19^5) points out that genetic change may reinforce existing differences in habitat preference through natural selection. Thue the habitat of Eutamias minimus oreocetes would be expected to be somewhat different than that of E.m. consubrinus or E.m. neglectus. The evolution of the latter subspecies appears to have been facilitated by an eastward extension of the species' range. Its subspecific differences are probably reflected in its behavior as well as its morphology. Therefore it is possible that its habitat preferences are also due in part to genetic inheritance• Habitat of E. minimus The habitat of E. minimus* has been reviewed by Sheppard (1965) and Larrison (19^7). Ten subspecies of E. minimus are characterized by living in dry sagebrush habitats; three subspecies live in alpine regions. The subspecies, E.m. borealis. caniceps. hudsonius and neglectus all occur in forested areas similar to those occupied by E. amoenus luteiventris (whose preferred habitat is generally semi-open or contains many openings in the forest). In general, E. minimus occupies the widest range of habitats of any North American chipmunk. In areas where it is the only species of Eutamias it occurs in forested as well as open regions. In areas of potential competition with other Eutamias species, E. minimus is res­ tricted to alpine or dry sagebrush. Neither of these latter habitats are characteristic for the genus as a whole except for E.m. consubrinus •Taxonomy is based on the work of Hall and Kelson (1959)* 5 and E.m* operaruis which occupy a wide range of habitats from sagebrush to alpine including forest edges, but generally more open habitat. Martinsen (1965) concluded that in Montana, E. minimus was more abundant on cut-over areas older than three years. was occupied by E. amoenus. The forested area Sheppard (1965) attempted to quantify the habitats of E. amoenus luteiventris and E. minimus oreocetes in Alberta. E. minimus predominated in open (unforested) areas which were supplied with a plentiful cover of rocks and stumps. He concluded, however, that E. amoenus was inhibiting E. minimus from using habitats containing more woody growth and in general, E. minimus is more tolerant of varied habitat types. The habitat of E.m. neglectus has been described by several authors. Jackson (1961) cites McAllister as stating that in northern Wisconsin it was found in coniferous, mixed coniferous and hardwood forests, particul­ arly if the ground cover contains various types of woody or rock debris and woody shrubs or combinations of these. wet wooded areas. Rarely did it occur in low Manville (19^9) describes its general habitat in northern Michigan as occurring in dense upland forests, conifer swamps, and along shorelines; recently burned or cut-over areas, rocky mountaintops, cleared lands and openings in the forest containing shrubby ground cover. Forbes (196*0 did not find this species in spruce-fir or northern hardwood forests in northern Minnesota. supported the greatest number. Disturbed areas within the forest He concluded that an open forest margin with rock, brush, or slash piles interspersed with bramble thickets, was a favorable habitat at least during the summer, and that E. minimus seemed to avoid dense cover. 1 was impressed with the observations that 6 certain very "open1* habitats, containing dense stands of bracken fern CPteridium aquilinum) or woody ground cover or both adjacent to pine stands, held few if any chipmunks. Conversely, relatively small contig­ uous clearings in cut-over forests were occupied by the species in fair numbers. It suggested to me that the degree of visibility and ground cover within the different kinds of "open" habitats needed to be evaluated. This led to two types of investigations: 1) An evaluation of the pattern of habitat use by this species in relation to the composition of the available habitat within a study area. 2) An experimental phase in which the effects of environmental parameters similar to those investigated in the field, were tested and evaluated. This work was an attempt to clarify the significance of the habitat factors investigated on the selection of habitat by Eutamias minimus neglectus in the Upper Peninsula of Michigan. FIELD STUDIES Introduction The objectives of the field work were an attempt to: (1) estimate the home ranges and movements of individual chipmunks in the study areas via a system of capture, mark, recapture, sightings and telemetry; (2) obtain information regarding the composition and density of the population} (3) compare the composition of the habitat within the home range with that of the total area; (4) attempt to determine the significance of certain features of the habitat in terms of their role in habitat selection by the chipmunk. Description and location of areas Experimental Areas I and II were chosen by reference to habitat descriptions reported in the literature (Jackson, 1961; Manville, 1949; Larrison, 1947; Sheppard, 1965; Forbes, 1964 and Martinsen, 1965 and the results of trial trapping periods. The areas were composed of diverse elements within their boundaries which would serve as "test" units. New experimental areas were established in 1967 and 1968 because of a change in my residency from Escanaba to Sault Ste. Marie. This relocation was an opportunity to test the process of predicting chipmunk habitat selection based on previous field and experimental work conducted in 1965 and 1966. All areas were located in Michigan's Upper Peninsula. Areas I and II were situated about seven miles southwest of Escanaba; Areas III 7 8 through V approximately 30 miles southwest of Sault Ste. Marie near the settlement of Raco. The summers are mild, the July temperatures averaging about 66 degrees F. near Escanaba and 62 degrees near Sault Ste. Marie; the January averages are 12 degrees F. and 10 degrees F. respectively. The Escanaba area receives about 35 inches of precipitation annually which includes approximately 55 inches of snow. The area near the Sault receives about 32 inches annually including 90 inches of snow. Most of the ^tO-year old forest on Area I was cut-over in 19&1. The uncut forest and remaining trees consisted of primarily red pine (Pinus resinosa), aspen (Populus tremuloides) and black spruce (Picea mariana) plus a scattering of white pine (Pinus strobus) and balsam fir (Abies balsamifera) (Figure I and Table I). The soil (Kinross mucky sand) had a ground water table within one to three feet of the surface. Associated with the more xerophytic conditions were various species of mosses, wintergreen (Gaultheria procumbens) and blueberry (Vaccinium s£.)• Labrador tea (Ledum groenlanaicum) and sphagnum moss (Sphagnum sp.) grew in the scattered moist depressions under a parti­ ally open canopy. Bracken fern was sparsely scattered under the denser portions of the forest; it was of medium density and intermittent distri­ bution under tree cover of medium density and among tree reproduction; and it formed a tall dense, continuous layer in the open, northeast portion of the study area. The brush pile ratings were established on a subjective basis described later. The periphery of Area II consisted of almost pure hemlock (Tsuga canadensis) of varying ages growing on Kalkaska sand (Figure 2 and Table I). The study area had been cut-over at different times; most recently in i960 and 1961, After earlier cuttings about 55 years ago, red maple Figure 1 Cover map of A DOMINANT T O R E S T T Y P E S e OPEN O f OREST A ASPEN B A S P E N ” RED MAPLE C RED P I N E - S P R U C E D RED P I N E - S P R U C E - A S P E N BRUSH PILE DENSITY UNDERSTORY V EG E TA TIO N I labrador t e a b low b lu eb erry f bracken fern 6 open DENSITY * sparse " m edium **• d e n s e © sparse © medium O dense • TRAP SITES Table 1 A summary of "tree densities for each Area's forest types. Measure­ ments indicate basal area in square feet/acre, stem count/acre and the distribution of the stems per size class (in per cent). Species Red Pine White Pine Jack Pine Hemlock Spruce White Cedar Fir Yellow Birch White Birch Aspen Red Maple Totals Stems/Acre AREA I Forest Types* A B C D Basal Area*-square feet AREA II Forest Types* A B C D Basal Area-,square feet AREA III Forest Types* A B C D Basal Area--square feet 1.6 4.5 3 .8 4.7 - - 32.1 - - - - - - - - 1 .0 15.5 - - - - 0.2 0 .4 - 37.4 15.5 - 6 .7 3 0.2 115.4 0 .8 55-1 22.9 — 55.1 - - - 2 .3 2 .3 2 .1 10.8 1 .5 1 .9 AREA IV Forest Types A B Basal Area-sq.ft 3 .9 1 .0 m - - - 7 .0 1 .2 0 .4 - - - - - - - - - - - - - - - - - - 0 .5 - - - - - - - - - - - - - - 6 .3 6 .3 0 .9 9 .4 10.6 6 .0 1.6 2 .3 7.0 14.7 0 .4 4 .6 1 .9 - 69.7 - - 2 .6 0 .7 **■ - - - 1 .2 8 .9 - - - - - - - 0 .4 0 .8 5.6 10.0 0 .5 1.7 4 .3 2 .3 0 .5 29.3 10.4 5 .2 43.3 136.7 28.7 13.3 6 .4 51.6 138.4 136.5 144.2 221.4 39.6 44.9 5 .7 27.7 91.6 12.5 27.4 38 112 192 521 452 750 460 680 284 43 132 186 160 117 89# 7# 4# 100# - 9 .1 28.9 3.1 - - ** - - 22.7 11.3 3 .5 — — — DBH Class 1 - 4" 5 - 10" 11- 15" 16- 20" 72% 28?6 9# 10# - - - - 33# 63# 2# 2% 53# 42# 3# 2# 4236 48# 10# - 67# 29# 3# 1# 69# 30# 1# 75# 25# 2# 6l# 33# 6# 31# 69# 90# 10# 49# 50# - - - - - - 4* - 1# *Refer to individual cover maps for a description of the forest type categories A, B, C and D. Figure 2. Cover map of Area II 11 DOMINANT FOREST TY P E BRUSH PILE DENSITY 0 OPEN OF0REST © sparse A HEMLOCK © m e dium B H E M L O C K - Y E L L O W BIRCH dense RED MAPLE C RED MAPLE - HEMLOCK» TRAP S I T E S WHITE PINE D RED MAPLE UNDERSTORY VEGETATION DENSITY hz ha z e l n u t *sparse rb red r a s p b e r r y "*»« m e d i u m sedge dense 12 (Acer rubrum) and yellow birch (Betula alleghaniensis) became established along with the previously mentioned conifer. They comprised the relative­ ly more mature trees in the center of the area. Hazel nut (Corylus sp.) was the dominant shrub of a sparse, tall-shrub layer with these hardwoods. Since the 19&2 cuttings, young red maple sprouts and saplings as well as conifer reproduction, have become interspersed throughout the cut-over area. Bed raspberry (Rubus idaeus) was very abundant in the more open areas. The composition of the low, woody vegetation under the forest canopy was primarily wintergreen, bunchberry (Cornus canadensis) and bristly dew­ berry (Rubus hispidus). The most common fern in the hardwoods was the woods spinulosa (Dryopteris spinulosa). Staghorn (Lycopodium clavaturn) and stiff (Lycopodium annotinum) clubmosses, as well as the pipsessewa (Chimaphila umbellata) were common. Bracken fern was sparsely scattered throughout the open and semi-open portions. The maps for Areas I and II were constructed from aerial photos taken at a height of about 200 feet by a private photographer, and cover mapping on the ground. Areas III and IV are in a relatively flat region. Rubicon sand sup­ ported a forest of jackpine (Pinus banksiana), red maple, red pine, aspen and white birch (Betula papyrifera)(Figures 3, ^ and Table 1). The tall shrub layer was very sparse consisting of an occasional juneberry (Amelanchier sja.). The woody ground vegetation was typified by bearberry (Arctostaphylos uva-arsi), wintergreen, sweetfern (Comptonia peregrina), blueberry and bush honeysuckle (Diervilla lonicera). The latter three species were the most common and of varying densities. Other common plants Figure 3 Cover map of Area III 13 scale I,,« I 2 5 ' DOMI NANT F O R E S T T Y P E S BRUSH PILE DENSI TY © OP E N FOREST C3> s p a r s e A A S P E N - W H I T E BIRCH & medium B A S P E N - JACK a n d R E D PINE ® dense C A S P E N - RED P I NE - WHI T E BIRCH D JACK PINE-ASPEN • TRAP SITES UNDERSTORY V E G E T A T I O N b l ow b l u e b e r r y h bush honeysuckle s sw eetfern g g ra s s f b r a c k e n fern DENSITY 'sparse " medium M* d e n s e - Figure h Cover map of Area IV DOMINANT F OR E S T T Y P E © OPEN O FOREST A JACK PINE - R E D M A P L E WHITE BIRCH B WHITE BIRCH -RED PINEASPEN BRUSH P I LE DENSITY sparse me di um dense UNDERSTORY V E G E T A T I O N b low b l u e b e r r y h bush honeysuckle s s w e e t f ern DENSITY # sparse " medium *** d e n s e 0 TRAP SITES 15 were reindeer moss (Cladonia sp.) and bracken fern (Pteridium aquilinum). The fern's density was medium to dense and its distribution was interwoven between brush piles throughout the area. With the exception of a few small, scattered jackpine and red maple trees, Area V was treeless and lacked tall shrubs. similar to that in Areas III and IV but less dense. The ground cover was Bracken fern was of sparse to medium density and scattered around the brush piles. Relatively wide grassy areas separated the rows of brush piles (Figure 5). The Areas III, IV and V were mapped from greatly enlarged USDA aerial photos and cover mapping on the ground. Plates I through V illustrate the Areas. One other site worthy of note was trapped. This was a 4-acre commercial cedar post yard about six miles west of Escanaba (Plate VI). No detailed records were kept, but at least 10 chipmunks were trapped. They were still reported to be "plentiful" after this trapping was com­ pleted. Plate I Figure 1. North corner of Area I Figure 2. North central portion of Area I Plate II Figure 3. South central portion of Area II Figure b. South east portion of Area II Plate III Figure North west portion of Area III Figure 6 . South central portion of Area III 18 Plate IV Figure 7- Central portion along trial, Area Figure 8. South west portion of Area IV Plate V Figure 9* Figure 10. Looking west from northeast corner of Looking south from northeast corner oJ Area V 20 Plate VI Figure 11. A trial trapping location having high density of chipmunks Figure 5 Cover map of Area V COVER T Y P E S 0 OPEN g grasses b Jow b l u e b e r r y BRUSH © & 0 0 PILE DENSITY sparse medium dense TRAP SITES MATERIALS AND METHODS Trapping There is no one acceptable method of arranging traps that has been agreed upon by all workers for use with even one species. system: I used the grid (1) its validity seemed to be supported by many workers, (Tevis, 1956; Tanaka, 1963; Wolfe, 1968; Blair, 1941). (2) Use of a grid system would facilitate analysis of the estimated home range of the animal's habitat. (3) Sheppard (1965) and Martinsen (1965) used the grid system to study E. minimus, and ray data would be comparable to theirs. All areas were measured using a compass and tape. formed a grid pattern. The trap sites No traps were placed in the open, instead their location was shifted 3 or 4 feet to a brush pile or similar dense woody ground cover. Trap sites were marked with a numbered stake to facilitate finding the traps and add uniformity to the trapping regimen. were about 3 feet above ground level. The stakes Only one trap was set per site. The trap, which was 3 inches by 12 inches, was constructed of 1/4 inch hardware cloth (Plate VII). It was operated by a treadle having attached to it a prop holding up a trap door which dropped by gravity when the treadle was tripped. The trap was staked down to prevent over­ turning, and partially covered by a small piece of burlap. metal sheath was soldered to the inside of the door. placed a 3 inch wire, hooked on one end. A 2-inch Into this was When the door dropped, the wire slid down through the metal sheath, through the wire mesh on the bottom of the trap thus locking the door down. 23 PLATE VII Figure 12. The live trap used 25 The bait* a mixture of rolled oats and peanut butter, was placed on a small rectangular piece of metal suspended 1 Inch below the top of the trap by a wire. Thus, the animal could see the bait even when look­ ing into the trap through the entrance door. This method lessened loss of bait to insects. Traps set overnight on Areas I and II caught too many nocturnal mammals. Therefore, they were set about dawn and checked around mid-day and early evening. Overnight sets were made on other areas. Not all sites in Area I were trapped simultaneously because I lacked traps during 19^5 • Approximately one-half of the area was trapped first, then the traps were transferred to the untrapped portion of the area. No traps were set on rainy mornings. However, this did not delay the trapping schedule more than one day. Three-day trapping periods reduced the effect of weather variables and the possibility of interference with the habitat and animal activity by the investigator. removed after the trapping period was terminated. All traps were This was done to help prevent a "loss of interest" which was described by Tropan and Wofciechowska (1967)* It was speculated that this "absence" would maintain a level of curiosity in the animals for the traps when they were re-introduced into the area. The trapped chipmunks were transferred to a wire cone. This was done by inserting the open trap into a black hood which had a wire cone attach­ ed to it. The animal ran through the hood and into the cone. While restrained, it was toe-clipped, marked with Nyanzol*, weighed, sexed and *The six animals from Area captured from Area V were III fitted with transmitters and animals not marked with Nyanzol. 26 its age estimated. The dye marking system used was similar to that described by Martinsen (1965). Blair (19*tl). The toe-clipping followed the pattern described by Since pelage moult appeared to begin shortly after cessation of breeding, adults had to be dyed again upon recapture. Chipmunks in Area V were tagged with different colored polyvinyl strips. A strip was attached to two collars; one was put around the animal's neck and the other around its abdomen. with the aid of 7 x 50 binoculars. usually followed visually. The animals were located Once an animal was sighted it was Sach time it reappeared, its location was classified as a new detection point. An animal moving 50 feet in contin­ uous view had one detection point; if it disappeared and reappeared three times, it had four detection points. Habitat analysis An Area was subdivided into habitat units by assigning the stake at each trap site as a corner of a unit. Since the trap sites weren't laid out in a perfectly square grid, the shape of each unit varied. This had little effect on the results since within each unit the evaluation was on a relative basis. This partitioning facilitated detailed analysis of the total habitat, one unit at a time. The habitat factors used for evaluating the environment were: (1) brush pile density; (2) the distribution of woody ground vegetation; (3) horizontal visibility; (*0 density of the overhead tall tree and shrub canopy; (5) light intensity. Cover maps provided the bases for the description of the five habitat factors. Their variability was then 27 subjectively ranked (Table 3)* listed in Table 2. The numbers of units in each area are Factor one was rated in the spring; factors two, four and five during the summer* Factor three was determined at two seasons; spring, prior to the emergence of the broadleaf vegetation, and summer. Further explanation is required for factors three and four. The horizon­ tal visibility was rated by an observer located at a trap site as he faced the sites located diagonally* from his position. If there were no appreciable obstructions at about 2 feet of height between him and the diagonally located trap stake, it was rated 0; a scattering of trees, shrubs or bracken fern gave a rating of 1; many dense clumps of vegetation between the two sites rated a 2; if the distance between the two trap sites was almost rated a 3. completely closed in with ahigh growth of vegetation, it was Two observations were madefrom each trap site stake (Figure 6) and averaged together for a unit rating. If a unit's average rating was 2*5 it was rounded off to 3*0. Subjective ratings used in biology have been shown to be fairly reliable if: (1) the observer is experienced; (2) only one person does the evaluating; (3) the same predetermined standards are used throughout the survey. These three criteria were met. Conclusions based on these and other methods are presented as being reliable as the techniques used. The light intensity for Areas I, II and III was measured and evaluated using a modification of a method described by Friend (1961). I used small, clear glassed, screw-capped jars into which one stack of 14 ozalid papers were faced through the side of the bottle; another stack faced up through the bottom of the overturned jar. Two jars were attached to a selected trap at dusk, one at ground level and the other at the top of the stake. •Frontal direction was used at the first and last row sites. Table 2 Descriptions of the criteria used to evaluate habitat factors on a unit basis within and between study areas. 28 1. Brush Pile Density No brush piles Most of the ground visible under the brush pile— sparse About 50S*> of the ground visible under the brush pile— medium dense Little of the ground visible under the brush pile— dense 2. Horizontal Visibility— evaluated at brush pile height of 2 feet above ground level Few visual obstructions or none at all— almost all of stake visible Scattered clumps or individual trees between the two points— at least 2/3 of the stake visible Many dense clumps between the two points— less than 1/3 of the stake visible Widespread dense arrangement of obstructing objects— stake not visible 4. 0 1 2 3 Distribution of Woody Ground Vegetation (less than three Eating feet in height) No low woody cover Less than 1/3 of the ground covered by woody cover Between 1/3 and 2/3 of the ground covered by woody cover Over 2/3 of the ground covered by woody cover 3. Eating Light Intensity and Canopy Condition (Rated when foliage present) Six or less ozalid papers exposed— less than 1/4 canopy open 6-8 papers exposed— canopy 1/4 open 8-10 papers exposed— canopy J>/k open Over 10 papers exposed— open— no canopy 0 1 2 3 Eating 0 1 2 3 Bating 0 1 2 3 Figure 6 The procedure used for evaluating the horizontal visibility of a habitat unit 29 LAST ROW FIRST ROW ?---------- I I HABITAT UNIT I V" DIRECTION OF LOCATION OF TRAP SITE STAKES OBSERVATIONS si 30 They were exposed for one full, almost cloudless day. The number of papers exposed provided a measure of light intensity. The selection of the stakes was on a random basis for each of the four canopy closure categories, 10 stakes within a category. sampled with 80 jars. Areas X and II were each Since Area V was virtually without a forest canopy, no measurements were taken* The individual habitat factor ratings for a particular unit were not averaged together because this would obscure their difference. The observed use of the habitat, as determined from home range data, was compared to the expected random use of the habitat. Only the actual data were used to make comparisons using the Chi Square test. differences were reported at the .05 and .01 level. Significant Quantitative des­ cription of the study areas is found in Table 3* Age and sex criteria The age classification criteria used by Sheppard (1965) and in part by Forbes (1964) could not be used without sacrificing the animals. fore, field techniques, although not as dependable, were used. criteria were (1) Bodyweight. There­ The Based on my observations, no adult male chipmunk trapped prior to July 1 weighed less than 34 gms. Forbes (1964) and later Sheppard (1968) presented data indicating that juveniles which usually emerge after July 1, have a bodyweight which averages less than 30 gms. He noted that the weight of juvenileB prior to August 1 averaged approximately 25 gm. Therefore, all male animals weighing 32 gms. or less were considered juveniles. tures. (2) Gonads and secondary sexual struc­ Breeding adults were distinguished from sub-adults when captured before July 1 by the swollen testes, evidences of lactation or size of Table 3 Quantitative description of the study areas: size, number of habitat units, number of trap sites and spacing. 31 Area Size (in acres) Number of Habitat Units* Number of Trap Sites Approximate Trap Site Spacing (in feet) I 5.3 104 126 50 II 4.2 72 90 50 III 6.2 130 154 50 IV 2.5 65 74 25-30*• V 6.6 130 156 50 •S e e F ig u r e 6 , page 29 . • • O b j e c t iv e f o r t h i s a r e a was p r im a r ily t o e s t im a t e p o p u la tio n s i z e . 32 female teats, or both. Thus, animals trapped for the first time prior to July 1 were classified as adult or sub-adult using the appropriate criteria. Once marked, they were not confused upon recapturing. Animals trapped for the first time during July and August were classified using criterion (1). However, after mid-August, the reliability of classify­ ing "new" captures was questionable. Population estimates No formal population estimating techniques were employed for the following reasons: (1) Most adults using the area regularly were thought to have been trapped and marked soon after the animals were exposed to the traps. workers. This pattern of capture is similar to that reported by other Some animals were trapped later but they appeared to be trans­ ient except for No. 14 in Area I. (2) Recruitment took place in July and few young animals were recaptured after the end of August* New juveniles captured in September were thought to be dispersing from other areas. (3) The basic assumptions to be used before various population estimating techniques can be applied were generally violated by the type of proced­ ures used in this study. Home range estimates In an attempt to recognize the influence of the factors mentioned by Stickel (i960), my data were collected on Areas I and II throughout the spring, summer and part of the fall seasons. This insured a wide variation in kind and quantity of food and cover available as well as variations in age, sex and reproductive condition of the animals in the area. cept of home range used in this paper was based on Blair's (1933) The con­ 33 definition. One of my prime objectives was to utilize the estimated home range and movement data as aids in interpreting the animal's habitat use. Many methods have been suggested for measuring home ranges (Hayne, 19^9; Calhoun and Casby, 1958; Stickel, 1954 and 1965; Mohr and Stumpf, 1966; Wolfe, 1968). ature. Brown (1962) and Sanderson (1966) have reviewed the liter­ Most methods are related to the procedure used for the determin­ ation of animal movement, trapping, visual observations, radioactive tags and telemetry; the latter two being relatively new innovations. used a combination of these, excluding the radioactive tags. I The minimum method of Martinsen (1965) was used because the data would be more mean­ ingful if the methods used and the results obtained were comparable with his data for the species. Animals with fewer than four detection points were not included in home range estimates or habitat selection analyses. Telemetry A miniature transmitter was used in 196? in an attempt to obtain more information about the movements of chipmunks. The trapping and tagging with the transmitter was carried out on August 22 and 23. The basic design is a modification of one developed by Cochran (mimeographed April, 1967) and was assembled according to the instructions given in his report. The modified design enabled me to utilize sill crystals designed for frequencies from 148.00 me. to 148.75 me. (Figure 9t Appendix). The transmitter's antenna was a copper wire loop fitted to the animal's abdomen while the animal was restrained. The loose end of the antenna was soldered with liquid to the transmitter to complete the circuit. The transmitter and battery were potted with a dental acrylic to protect JM it from shock and water. Both were affixed with a silicone glue to a 2 inch long piece of thin polyvinyl. This strip was then snapped to another strip tfhich served as a fitted neck collar. The completed trans­ mitter formed a back-pack which weighed approximately 7.8 gm. It was prevented from slipping off the animal's back by the relatively snug fit of the collar and antenna. A captive chipmunk was used to test the harness' fit and behavioral effects. noted. No apparent adverse effects were Plate VIII illustrates the complete "package". Receiver model DC *t603 was a 12-V battery operated 6-transistor car radio. To its circuit was attached am International TRC-3B transistor­ ized converter. It converted the radio to a receiver capable of receiv­ ing signals from 148 me to 1^9 me. The directional antenna used to receive the signals was a 6 element Yagi especially cut according to specifications described in the Radio Amateur's Handbook (39th edition, 1962). A coaxial antenna cable, reson­ ant with the operating frequency, connected the antenna to the receiver. The antenna was to be attached to a 20 feet long pole that could be rotated 360°. indicated that Field tests of the transmitter in dense, brushy habitat yards was about the maximum distance that the signal could be perceived whether the antenna was elevated 20 feet or 6 feet. However, when the chipmunk was sitting in an exposed location, the effec­ tive signal distance was as much as 123 yards. No signal could be detected if the animal was in an underground den. Due to these limitations, a harness type, over-the-shoulder sling was constructed for the receiver, converter and 12 V battery. Signals were located while walking slowly down the'logging trails which criss-crossed the area. Pausing frequent­ ly, the antenna was rotated 360° in an attempt to locate the direction Plate VIII Figure 13 . Transmitter, uncoated and coated with denture material 35 fill 11 111 It 111 IIIIIIIIIIN M i ll I H 11111 M M M IM1 1 M 56 of an emitting signal. When one was received, its location was deter­ mined by triangulation from two points about 20 yards apart. cedure was used for each signal that was detected. This pro­ A moving animal was "tracked" until it settled down to one spot for about five minutes. A lth ou gh a " f u n c tio n a l" s c h e m a tic was u s e d , u n e x p e c te d d i f f i c u l t i e s were e n c o u n te r e d w ith th e t r a n s m i t t e r . s e n s i t i v e enough t o o s c i l l a t e . ( 1 ) Not a l l o f th e c r y s t a l s were T h is n e c e s s i t a t e d revam ping th e s c h e m a tic . (2) To o b t a in a s i g n a l t h a t c o u ld be r e c e iv e d a t a " r ea so n a b le " d i s t a n c e , a s p e c i f i c a l l y c u t r e s i s t o r was n e c e s s a r y w hich in c r e a s e d b a t t e r y d r a in and sh o r te n e d i t s l i f e . ( 3 ) I t was n e c e s s a r y t o u se a h ig h fre q u en cy wave le n g t h (l*v8 me) i n o r d e r t o o b t a in th e n e c e s s a r y d i r e c t i o n a l q u a l i ­ tie s . Working w ith t h i s fr e q u e n c y p la c e d a premium on th e d e l i c a t e a r t o f c o n s t r u c t io n . S l i g h t a l t e r a t i o n i n th e w in d in g o f th e L 1 c o i l r e s u l t e d i n e f f e c t s v a r y in g from no f u n c t io n t o th e p r o d u c tio n o f a non­ o s c illa t in g s ig n a l. T e le m etr y was n o t u se d i n 1 9 6 8 . V o c a liz a t io n s Another method of locating chipmunks was by noting the location of their vocalizations. If an animal emitted any of the calls associated with fear or warning, the observer was usually quite close to the general location of the animal noted. One type of call, a soft "Qwip" or "Whoit", was frequently heard late in the day. In an open area, and depending upon weather conditions, the call could be heard 100 yards. of the number of locations at which this call was heard. Records were kept On every occas­ ion, the animal was perched in a very conspicuous elevated location. The enumeration of vocalizations was based on the number of different locations 37 at which the call was heard. Thus, the location at which an animal was observed calling, was designated as one call regardless of how many indi­ vidual calls he emitted per time length at that location. changed locations and If the animal began callingagain (which was noted very frequentl it was considered a "new" location. RESULTS Home Range D e te r m in a tio n s Advilt males had larger home ranges than females, and adult males larger ones than juvenile males (Tables 4 and 5)- The juvenile females had larger home ranges than those of the adult females. situation may have been due to: This latter (1) a greater affinity of adult females for the nest site; (2) the restricted movements breeding females had dur­ ing late pregnancy and lactation; (3) the tendency to capture adults less frequently in late summer than in the spring; (4) the possibility that the "home range" of juveniles may tend to increase as they grow older due to exploration and dispersal. Thus, a reportedly smaller home range for adult females vs juvenile females may be an artifact produced by one or more of the aforementioned set of circumstances. The estimated home ranges for each area were combined and outlined on individual maps (Figures 13 through 20, Appendix). Included on each map is the outlined area of home ranges for adults only, as well as for all animals combined. A larger home range composite for all animals may be explained by the tendency for juveniles to explore portions of the habitat apparently unused by the adults; this may be preliminary to their dispersal. Telemetry provided additional detection points in Area III which resulted in a home range map having a considerable clumping of points. As a result, the most frequently used portion of the habitat for this season was more easily discernible. The calculated home range with 38 Table 4 summary of home range data for males Area I II III V No. of Animals Estimated Age No. of Months of Observation Total no, of times seen per visit to area Total no. of Detection Points (1) Average Estimated Home Range Minimum Method (in acres) Average of Farthest Move­ ment Recorded (in feet) 59 0.65 282 45 0.79 346 7 32 0.30 223 3 10 33 0.50 275 A 1 8 78 0.80 419 3 J 1 7 3k 0,73 304 4 A 2 17 97 1.15 425 15 Adults 0.77 332 13 Juveniles 0.68 309 5 A 7 4 J 7 4 A 3 6 J 2 Averages for the: 6 (1) Includes trap data, daily visual observations and telemetry points. vO Table 5 A summary of home range data for females Area I II III V No. of Animals Estimated Age No. of Months of Observation Total no. of tim es seen per v i s i t to area Total no. o f D etection P oints (1) Average Estimated Home Range Minimum Method (in a cres) Average o f F arthest Move­ ment Recorded (in f e e t ) 5 A 7 3 4o 0.49 223 2 J 7 11 18 0 .8 1 301 2 A 3 3 12 0.54 225 3 J 3 4 22 0.62 289 1 A 1 6 33 0.86 350 5 J 1 2 96 0.64 292 3 A 2 4 29 0.38 194 11 Adults 0.57 224 10 Ju v en iles 0.69 295 Averages fo r the: (1) Includes trap data, v isu a l observation p oin ts and telem etry p o in ts. -p- o *a telemetry still included some points which appeared to be exploratory sallies. They were more easily detected from the main concentration of points and range use. Data from Table 6 indicate that the adults trapped in 1966 were the same animals trapped in 1965* The adult male (#7) which died in July* 1965 was replaced that month by a sub-adult (#1*0. present in 1966. The data also suggested that: This animal was still (1) all the juveniles trapped in Area I had dispersed by the next breeding season; (2) some hierarchial system of behavior may have been affecting the population structure. Certain home ranges contained breeding adults which were residents surviving from the previous season. The juveniles, which probably were of a "lower” hierarchial status, disperse. Other authors have suggested similar behavioral interactions. Seasonal Behavior of Habitat Selection Data obtained from evaluating horizontal visibility and light inten­ sity were considered to be most important during the summer based on the following rationale. Most mating appeared to take place prior to the emergence of vegetation (approximately late May or early June). Various workers (Wecker, 1963; Thorpe, 19*+5; Allee et al., 19**9) have suggested that the behavior of habitat selection, which is the basis for establish­ ing a breeding unit within the environment, is in part innate. Based on this premise, it was assumed that young of the year dispersing from the parental home range are biologically capable of selecting a habitat which could serve as a "functional" home range. Of the five habitat factors considered, horizontal visibility, overhead cover and light intensity are the ones most affected by the change of the seasons. This Table 6 Trapping effort and success for Area I, 1965* and 1966. 42 CAPTURE DATES Chipmunk Number and Age 1 2 3 if 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 A A A A A A A A J J J J J A J J J J J A p r il June May 28-29 1 -5 1 5 -2 0 X X X X X X X X X X XX X X X X X 1 -6 X X X X X X X J u ly 1 5 -2 0 1 -6 X X X X X X XX XX X XX XX X Aug. S e p t. 1 5 -2 0 1 5 -2 0 2 1 -2 6 X X X X X X X X XX XX XXX XX X XX XX XX X X X X X X X XX XX X X X XX X XX X X XX XX T o ta ls 6 7 6 5 4 8 6 6 6 4 6 5 4 6 3 2 1 2 2 1966** 1 -3 1 2 3 4 5 6 8 14 A A A A A A A A X XX X X X XX XX XX 1 -3 X X X X X X XX X • Sixty-three traps set each trapping day except eighteen in April. *• One hundred twenty-six traps set each trap day. 2 3 2 2 2 3 4 3 ^3 seasonal change is most pronounced in the latter part of September as the vegetation dies back. Few juvenile recaptures were noted in mid- September when food resources waned and baited traps would seem to be even more attractive. The data suggested that the lack of capture could be merely affected by the trapping procedures, or that the juveniles had dispersed seeking their own habitat prior to the onset of hibernation. Therefore, the selection for the establishment of their home range would have to be based on the condition of the ground vegetation by midSeptember. In some areas studied, the vegetation retained the summer aspect but was beginning toshow the onset of fall. Those portions of the environment which appeared to provide habitat, as evidenced by occup­ ancy of breeding adults, appeared to have similar habitat ratings for either season. However, ratings for unoccupied portions within an area changed considerably from September to October. Animal Density and Distribution The Areas ranked in decreasing order of adult animal density were II, I, V, III, and IV (Table 7)« The same ranking order was obtained when comparing the computed density of all animals. density of the habitats was easily categorized (II, Since the vegetation I, IV, III, V in decreasing order of density), it appeared that the denser the habitat, the smaller the home range and the denser the population. Habitability is based on the percentage of the total area used by the adults and also by all animals (Table 8). The Areas ranked by the amount of acreage com­ prising the estimated adult home ranges, were in decreasing order: V, III, I, II, IV; when all home ranges were considered the order was III, I, II, IV. Since Area V was investigated during the spring and only an Table 7 Estimated chipmunk densities based on the habitat estimated to have been used by the animals. Mt Area Number of sexually active adults Density of sexually active adults per acre based on the habitat used Number of Adults Density of adults per acre based on the habitat used Total Number of Animals Density of all animals per acre of used habitat I 8 3.0 8 3.0 19 5.0 II 6 3.2 7 3.7 17 5.6 III ? 5 1.3 15 ^•9 IV l 0.3 2 0.5 2 0.5 V 8 1.9 9 2.1 9 - •Area investigated in spring when no young of year present. Not Comparab! Table 8 Estimated use of an area's habitat by animals of different age. Use is determined from home range data. ^5 Area Total size in acres Estimated area used by adults Percentage used by adults Estimated area used by all animals (in acres) Percentage used by all animals I 5.3 2.7 .51 3.8 .72 II k.2 1.9 .Vf 3.0 .71 III 6.2 3.9 .63 ^•5 .72 IV 2.5 0.3 .12 0.3 .12 V 6.6 *K3 .65 Not Comparable* •Area investigated in spring when no young of year present. 46 adult population was present, it was not comparable for ranking with the latter group. However, assuming some young would be raised, the total area of recorded use would probably be expanded. The data in Tables 9 and 10 were used to test the null hypothesis that the chipmunks were randomly distributed (Table 11). The v a l i d i t y f o r t h i s c o m p ila tio n o f d a ta c o l l e c t e d from i n d iv i d u a l a n im a ls was a t f i r s t c o n s id e r e d t o be a p rob lem . If th e d a ta were to o v a r ia b le betw een i n d iv i d u a l a n im a ls i t would be h e te r o g e n e o u s and t h e r e ­ f o r n o t be com p arab le. A lth o u g h th e number o f h a b i t a t u n i t s v a r ie d w ith th e s i z e o f th e home ran ge o f ea ch i n d i v i d u a l , th e tr e n d s o f h a b i t a t u se f o r i n d iv i d u a l a n im a ls o f th e same a g e , s e x and a r e a a p p ea red hom ogeneous. Statistical analysis Use of Chi Square requires: (1) that the data not be in percentages and (2) that there should be an expected value of at least five for each class. The first was strictly adhered to; the application of the second varied somewhat partly because of separation of the data into age, sex and area comparisons. Pooling of more of the data would have increased the sample size, but also increased the probability of heterogeneity. Slight variation in the application of the second criterion was thought to be less serious than the "masking” effect from increased heterogeneity. Four of the six Chi Squre values obtained from juvenile use of brush piles were statistically significant. One value was significant for adult males and one was significant between the .06 and .10 confidence interval. Two of the four values for adult females were significant between the .06 and .10 confidence interval. Examination of Tables 9 &uid 10 indicates that juveniles and adults used brush pileB with the higher density ratings. This may be explained for the juveniles by an initial attachment the young may Table 9 Percentage of the habitat units in each category for the habitat fact occurring within the estimated home range of chipmunks for all areas Area Age Sex Brush P ile D ensity Sample S ize EAB I TAT 0 1 2 Horizontal V is ib ilit y Ground Cover 3 0 RATI NG 1 2 3 Overhead Cover CAT E G0 R I E S 0 1 2 3 0 1 2 3 A A M F 4 4 0 0 .45 .37 .18 .52 .29 .17 0 0 .17 .51 .31 .10 .57 .32 .25 .43 .22 .08 .26 .45 .25 .05 .01 .25 .20 .52 .05 .29 .21 .44 J J M F 5 2 0 0 .46 .38 .16 .38 .42 .18 0 0 .10 .60 .30 .04 .38 .57 .12 .42 .31 .15 0 .19 .57 .23 0 .25 .66 .38 0 .57 0 .4? A A M F 4 2 0 0 .03 .15 .82 .04 .22 .72 0 0 .06 .61 .33 .18 .50 .31 .76 .15 .09 0 .04 .13 .13 .04 0 .03 .18 .79 0 .04 .17 .85 J J H F 5 3 .02 0 .06 .41 .51 .02 .17 .82 0 0 .17 .57 .26 .8 .60 .3 .56 .15 .17 .13 .71 .11 .11 .60 .07 .28 .07 .58 .02 0 .22 .75 A A M F 2 1 0 0 .31 .43 .24 .32 .63 .05 0 0 .38 .43 .18 .36 .53 .10 .50 .24 .08 .18 .58 .36 0 .05 .01 .06 .19 .72 0 0 .06 .94 J J M F 2 5 0 0 .16 .27 .55 .19 .60 .21 0 0 .38 .55 .05 .23 .59 .19 .55 .27 .05 .11 .55 .31 .01 .13 0 0 .22 .78 .04 .02 .13 .80 A A M F 4 3 0 0 .30 .52 .15 .31 .59 .10 0 0 .27 .48 .24 .21 .58 .21 .61 .07 .04 .23 .65 .07 .07 .21 1 TT IX II I V 1.00 1.00 Table 10 Percentage composition of the habitat units in each category for each area's habitat factors. t Brush Pile Density Area Ground Cover HABITAT 0 I .03 1 2 . 46 M 3 0 .08 1 Horizontal Visibility RATING 2 3 .01 .26 .47 .26 Overhead Cover CA T E G O R I E S 0 1 2 3 .17 .26 .34 .23 0 1 2 3 .16 .25 .21 . 39 -r 00 II .06 .18 , 3k ,k 2 .01 .26 .50 .23 M .15 .18 .26 .11 . 35 .16 . 37 III .02 .32 A 3 .22 .02 . 44 . 42 .12 .43 .19 .08 .30 .10 .07 .18 . 64 V .02 . 39 .02 . 31 . 47 .20 . 37 .08 . 03 .52 . 13 Table 11 A summary of Chi Square values. These were obtained by comparing the estimated utilization of habitat factorB within the habitat units with the habitat composition of the area. 49 A reas I II III V Sam ple S iz e Age S e x Ground C over H o r iz o n ta l V is ib ility O v erh ea d C o v er 5.28 3.07 ** 12.19 * ** 12.64 7.51 ** 12.84 4.48 •* 15.56 * 11.76 * 9.22 8.96 3.28 ** 36.30 ** 17.93 *• 30.60 ** 18.26 B ru sh P i l e D e n s ity 4 A M 4 A F 5 J M 2 J r 4 A M 3.53 * * 15.18 2 A F 6.98 1.46 7.21 • 8.57 ** 18.44 *m 37.23 6 J M 3 J F 6.10 m* 27.62 2.74 * 7.62 6.98 •* 19.33 2 A M 2.63 4.27 1 A M .63 2 J M 5 J F 5.41 ** 12.50 * 10.52 5.84 *• 12.52 1.12 * 15.76 4 A M 6.27 3.38 3 A F 2.25 2.84 •Significant at the .05 to .03 level at 3 df. ••Significant at less than the .03 level at 3 df. 4.50 ** 19.83 •* 49.22 ** 27.21 10.33 ** 28.75 *• 15-93 7.25 2.82 9.36 50 have to the area near the nests. Animals appeared to use different degrees of woody ground vegetation in a random fashion. Ten of the Ik Chi Square visibility values were significant or highly significant (Table 11). These values reflect a significantly greater use of habitat units rated as having high horizontal visibility thsui would be expected by chance. Con­ versely, the chipmunks UBed units with low horizontal visibility ratings less than expected. The significant values for overhead cover stem from greater use of units with high light them low light intensities. Vocalizations As mentioned in another section, I made special note of ventriloquistic calls which I described as "Qwip". It was heard most frequently in the spring and late summer and in late afternoon to early evening (Figure ?)• Chipmunks used in the experimental enclosure were also heard issuing this call under similar time and conditions as those obtained under field conditions. It will be noted that few calls were heard during July but they were recorded for mid-August and September. Figure 7 Relation of the number of Qwip calls heard the month of the year TOTAL NUMBER of ‘QUIPS' HEARD per 10 HOURS in THE FIELD FOR ALL AREAS. 5 oi I I ■■ * 20 H > Oi N 01 O OJ 01 "0 X ui H DISCUSSION Evaluation of different areas for chipmunk habitat has been attempted. It is based on the estimated home range in relation to the use of certain elements within the habitat and by the density of the home ranges (those supporting animals in the breeding condition). ture suggests that The litera­ minimus neglectus is quite varied in its habitat utilization but by-and-large an animal of the forest openings or semi­ forested areas. Home range data were necessary to confirm which portions of the habitat were utilized by E. minimus but one or more of the following factors can alter their reliability. Hayne (1950) found a positive relationship between apparent home range and distance between traps. Stickel (195*0 pointed out that a closer spacing of traps produces smaller home range estimates— wider spacing, wider home range estimates. Thus, she considered trap spacing an important element of home range measurements. feet, Manville's (19*^9) every 30 feet. My traps were every 50 Both Martinsen (19&5) and Sheppard (1965) spaced their traps every 100 feet. The size of the home ranges presented by the latter workers were con­ siderably larger than those presented in Tables and 5 . This may be ex­ plained by their wider trap spacing and/or the fact that these authors investigated habitats considerably less cluttered with large environ­ mental objects (e.g. brush piles, trees, woody shrubs) allowing for con­ siderable visual "access". An exception to this latter situation was the work of Manville (19**9) who trapped in habitats in the Upper Peninsula which were denser them those discussed in this report. 52 Seven adults 53 that he trapped had an average home range of 0.2 acres, compared to 0.7 acres from my data. His method of estimating the home range was some­ what similar to that used by Harvey and Barbour (1965) which would result in smaller home ranges estimates vs the minimum method which I used. Jackson (1961) also reported a home range of less than one acre for E. minimus in northern Wisconsin. My data indicate substantially smaller home ranges for E. minimus in northern Michigan than in the western portion of its range. The greatest distance traveled between two points is another reflectior of the range of this species. 512 feet for nine animals. Martinsen (1965) reports an average of Sheppard's data, although not strictly com­ parable, indicated that his average animal covered greater distances than did mine. Manville reported an average of 229* for two adult males and 171' for four adult females; a small sample but still similar to my data (Tables and 5)* Jackson (1961) and Martinsen (1965) cited instances where various species of Eutamias had moved from one area to another in order to obtain an especially abundant, preferred food. It seems logical that baited traps would have their greatest "appeal" during early spring when food resources are minimal. From the data available, I could not attribute to the lure of the bait any distortion of the animal's movement pattern at any season. Successful trap sites were generally in close proximity to other sites which never had a chipmunk caught at the site. During the summer, the bait had to compete with natural foods which were generally plentiful to very abundant. Juveniles appeared to be more susceptible to trapping during this season than the adults. This may have been due to their in­ experience with the traps, naive curiosity, or a greater need for a variety 54 of food due to higher rates of metabolism and growth or some combination of these factors. However, up to mid-August they also confined their movements to certain habitats regardless of the baited traps present in a different habitat fifty feet away. It is concluded, therefore, that in general, distribution of the food resources in the traps had little effect in significantly altering the size of the home range between the spring and summer seasons. Jorgensen (1968), Quadagno (1968) and Sheppard (1965) stated that competitive exclusion may influence home range size and therefore animal distribution. This interference would most likely come from an animal having about the same size, activity pattern and habitat as Eutamias. Tamias striatus was the only similar animal in some of the study areas. However, I collected no data to evaluate their interrelationship; the literature (Forbes, 1964) does not contribute enough to make any inter­ pretation of competitive exclusion. From my data I can neither prove nor disprove that E. minimus is territorial. I observed active chasing in the spring on two occasions by unidentified animals. A review of the literature (Sheppard, 1965; Martinsen, 1965; Forbes, 1964; Criddle, 1943; Jackson, 1961; Larrison, 194?) des­ cribes some chasing activities, especially in defense of artificial food supplies. However, there is little or no supportive evidence for "true" territorial behavior. Describing the vocalizations of an animal in phonetic symbols is sub­ jective. Thus, calls described by various workers which may actually be the same, may be phonetically expressed in different word forms. Shep­ pard (1965), Gordon (1963), Larrison (194?), Broadbooks (1956) and Miller (1944) have attempted to correlate the vocalizations of E. amoenus I 55 or E* mini mus alarm) have or defense, be en bo th scolding, reported. the behavior the "territorial" amoenus, not of and appear environment, if sound and for E. stimuli. would The asso cia te d an w i th was males wi th in each ly me impression gi vi ng those I A chipmunks speculate ing the that inclination similar s u ch as type the wi th of that developing drumming juvenile a of a ru ff ed has w h ic h grouse, call type wo ul d the summer of the These be expected po rt ion br ee din g of the season Ce rt ain were co nsistent­ used posts. were Most juvenile expr ess ed habi tat reported B o n a s a in did females. animals the to E. piles. than been for or slash with similar The pa rt icu la r in is site range the It el ev ate d "calling" late asso cia te d agonistic during home space behavior or an frequently matu rat io n be a m o e n u e . projection during es ta blishing E. stumps were to Br oa dbo ok s alarm frequently they call ing and indicating "territoriality" following. from tree C a l l s an d call as fear, es timated physical toward well oc cupancy more animal's observed as sound most mu ch locations the Larrison usually heard "Qwip" on any maxi mum reaction. dominance pe rformed animal's was by wi th but enhance the mini mus It shrubs call hawk, based described associated e . g . behavioral escape, spacing call designated habitat. their in te rpr et ed social be environmental co nditions I Miller to wi th for for a males. de ve lop­ themselves. other u m b e l l u s , of anim als (Trippen- s e e , 19^8). My data suggest habitat more frequently At least sites to or insure were two with adequate to few chipmunks, w h ic h explanations those gathered that are provides this. them possible. environ me nt al dispersal test regardless of their Some sort of good age w i t h obstructions "territorial" visual sex ho rizontal Habitats of o r may use visibility. el ev ate d be call. cont act a a perc hin g pre-requisite Not enough between data animals 56 may be necessary for maintenance of population stability. Thus, in a "good” habitat the animal cam perch on brush piles having exposed, elevate branches that provide a reasonably open view of the surrounding habitat and movement of other chipmunks (as well as readily available escape cover). Although this predilection for exposed situations would seem to increase the animal's vulnerability to predation, E. minimus can move very quickly and possibly avoid many winged predators. Other authors have also made note of their alacrity (Forbes, 196^; Jackson, 1961). The data also indicate greater use by juveniles for medium to dense brush piles. No habitats having rock piles, old buildings, and other such cover were investigated in detail, however, I would assume that adequate escape and nesting den cover in any form would suffice. fore, brush piles per se are not critically important. There­ The literature makes frequent note to the use of the latter type of cover by E. minimus. The significantly greater use of habitat units with little overhead cover may be interpreted several ways. (1) The overhead cover in the densely stocked conifer stands of Areas 1 and II had closed canopies, very sparse woody shrub growth at the ground level and no brush piles but did have many tree stems which reduced horizontal visibility in vary­ ing degrees. No areas were studied that had much overhead cover and spars tree or tall shrub stem stocking. Because these two conditions were not independent, data from field studies cannot be used to differentiate their independent significance. (2) Increased overhead cover may increase the probability of winged predation. (3) Overhead cover (and therefore reduced light intensity) would be responsible for differences in the ambient temperatures between the shade and the open. If the animal's metabolism was such as to be affected by environmental temperatures, 57 then the degree of shade may produce an avoidance behavior. The effect of overhead cover (reduced vertical visibility) was tes­ ted in the experimental enclosure to be described later and the data presented at that time. PEN EXPERIMENT Introduction The initial field work led to hypotheses that could test the significance of specific environmental elements in habitat selection. The following elements were investigated: (l) use of pens having different vertical and horizontal visibility; (2) use of perches with two different heights; (5) individual difference between chipmunks. were found to be testable from preliminary work. These variables The variables, light intensity, solar radiation and relative humidity were also tested in earlier experiments but were not found to be worthy of further investi­ gation. MATERIALS AND METHODS Apparatus The test apparatus consisted of a multiple choice enclosure (Figure 8) The structure was located on the edge of am abandoned field in an area containing very short grass (Plate IX). Food was passed through a long tube into a #10 can located in the center of the enclosure. Water was provided from a reservoir through a hose to a dish near the can. and water were supplied to maintain an excess. corn and rye seeds was used for food. The food A mixture of sunflower, Two layers of similarly arranged boards provided uniform escape cover at the ground level in each pen. Each chipmunk had free access to any of the eight pens. Each pen had only one opening which was guarded by two micro-switches to ensure a recor 58 Figure 8 The construction details of the experimental enclosure 59 PERCHS BOARDS WATER RESE.RVOIR FOOD TUBE DIMENSIONS DIAMETER - 10' LENGTH OF INSIDE SIDE WALLS ~ 4* PERIMETER LENGTH OF OUTSIDE WALLS OF INDIVIDUAL PEN S - 2.5* PERIMETER LENGTH O F INSIDE END OF PENS - 7 " COVER EACH PEN CONTAMED 2 TIERS OF BOARDS. EACH TIER SEPARATED BY 2 " SPACERS. Plate IX Figure 14. Experimental enclosure 6l of ingress and egress. Electrical contact of one or both of the switches activated one of 16 electromagnets in a common return, Esterline-Angus 20 pen recorder. This moved an inked recording pen which marked the event in one of the paper's 16 columns which turned on a motor driven chart. All perches were wired to the recorder to detect their use by an animal. They were designed to convert to a 16" or 2**" height. Horizontal visi­ bility was restricted by suspending double thicknesses of burlap at the appropriate height on the outside periphery of the desired pen. A double thickness of burlap laid on top of the enclosure restricted vertical visibility. Experimental design The three treatments, horizontal, vertical visibility and perch height were applied in a random fashion to each of the eight pens. One chipmunk had all eight differently treated pens available to him at one time. This exposure lasted for 2b hours*, which was considered one trial. Four trials (with four different chipmunks) comprised one replication. The entire experiment using the same four chipmunks was replicated four times, therefore a total of 16 trials were conducted. The order, sex and age in which a chipmunk was selected for use was also random. experimental design was basically a split-plot (Snedecor, 195&). The The treatments consisted of: (1) an open pen; no treatment; control (V) vertical visual restrictions for a pen with a 16" perch (H) horizontal visual restrictions for a pen with a 16" perch (VH) a combination of restrictions applied to a pen with a 16" perch (VP) restricted vertical vision to a pen with a 2bu perch •The chipmunk was introduced into the enclosure during late afternoon* 62 (HP) (P> (VHP) restricted horizontal vision to a pen with a 2^" perch an open pen having a 2h%% perch a combination of restrictions applied to a pen with a 2k,t perch RESULTS Pen utilization Assumption of randomness was met by the nature of the experimental design. A normal distribution was obtained by adding one to all numbers and the data were transformed to logs. Homogeneity of variance was exam­ ined by the analysis of the data for interactions. The data were treated by analysis of variance working with four factors. Some trials failed to produce data because of various equipment failures. These missing data were treated accordingly to Anderson’s (19*+6) missing plot technique. The F test was used for estimating the probability of obtaining the results reported by chance (Table 12). The highly significant values for the combined treatments or perch height-horizontal visibility (HP) and vertical visibility-horizontal visibility (VH) indicate interactions exist. The F values for main effects - different perch heights in the pens, restricted horizontal visibility and restricted vertical visibility were highly significant (Table 12). The separate effects were tested and examined but since they are not ortho­ gonal they are interpreted conservatively (Tables 13 through 15)• The test data from Table 13 indicate a highly significant F value for the main effect and horizontal treatment in all cases except one. This suggests a reduced use of pens treated with restricted horizontal visibility. The two highly significant F values from Table 12 for separate effects indicate that restricted vertical visibility appeared to result in a significant reduction of pen use even if those pens had no 63 Table 12 The final results of statistical treatment of one phase of the experimental design. These data were compiled from measurements of minutes spent by each of the four chipmunks in the eight pens exposed to different treatments. 64 Source Whole Pl Ch Re Er o i p r ts ps s or s sa df ms 40.01 11.02 21.92 7.0? 15 3 3 9 2 .6? 3.67 7.31 .79 2.99 73.10 16.67 10.80 l.l4 14.66 5.43 3.03 2.33 .52 8.46 2.20 1.54 4.98 88.27 1 1 1 1 1 3 3 3 3 76 287.33 119 F 4.65 Treatments P H V PH PV HV PC HC VC PH PH HV CV PV Er V C C P CH ror b Totals **Significant at .01 level 1 3 3 3 1 2.99 73.10 16.67 10.80 1.14 14.66 1.8l 1.01 .78 -52 2.82 .73 .51 1.66 1.16 2.58 63.02** 14.37** 9.31** .98 12.64** 1.56 .87 .67 .45 2.43 .63 .44 1.43 Tables 13 through 15 Analysis of the interaction data, PH, HV and PV for the separate effects of horizontal, vertical and perch height treatments. The values reflect the minutes spent by all chipmunks in a pen. Table 13 Analysis for the separate effect - Horizontal treatment. 65 No Horizontal Restrictions No Vertical Restrictions Horizontal Restrictions Difference F Values 75.84 51.26 44.58 50.077*• Vertical Restrictions 55.79 55.44 20.55 11.896** No Vertical Restrictions 72.95 49.65 25.50 15-60** 49.66 44.56 5.50 16" Perch 24" Perch Vertical Restrictions .806 Table l4 Analysis for the separate effect. Vertical treatment. 66 N o V e r t i c a l R e s t r i c t i o n N o H o r i z o n t a l R e s t r i c t i o n s 16" 24" H o r i z o n t a l R e s t r i c t i o n s 16" 24" V e r t i c a l R e s t r i c t i o n D i f f e r e n c e F Valu es 75.8** 55.79 20.05 11.550*• 72.95 49.66 23.29 15.586** 31.36 35-^ 4.18 .501 49.65 44.36 5.29 .803 P e r c h P e r c h P e r c h P e r c h Table 15 Analysis for the separate effect, the influence different perch heights on pen use. 16" Perch 2*+M Perch Difference F Values 75.8*t 72.95 2.89 •2*+0 55-79 *+9.66 6.13 1.079 31.26 *+9.63 18.39 35.^ *♦*+.36 8.92 No Vertical Restric tions No H o ri zon ta l R e s t r i c t i o n s Vertical Restrictions 9.718** No Vertical Restrictions H o r i z o n t a l R e s t r i c t i o n s Vertical Restrictions 2.286 68 horizontal restrictions and regardless of what height perches are in the pens. In pens having horizontal restrictions and vertical restriction, just the presence of the burlap (visibility restrictions) may produce some type of avoidance behavior. This could also hold true for reduced use of pens with horizontal restrictions. The overall pen use was much less for pens with horizontal treatment than for pens without horizontal treatment* The presence of horizontal, restrictions depress pen use about the same regardless of the application of vertical treatments. This suggests that horizontal treatment "over-rides" any effect of the vertical one. Perch utilization Pens having a higher perch were used significantly more when they were treated with a horizontal restriction but no vertical restriction (Table 15)* There was no significant difference between the use of pens having either of the two perch heights and both types of visibility restrictions. The data indicate that animals used pens with horizontal visibility restrictions significantly less. Pens having both high perches and hori­ zontal visibility restrictions were used more than those pens with just horizontal restrictions; even more if there were no vertical restrictions on the pens with horizontal restrictions and high perches. No interactions indicates that all between chipmunks chipmunks behaved and treatments similarly to all were the noted, which treatments. This would be expected if any innate behavioral mechanism was influencing their habitat selection. The. data obtained from the perch use by the different animals are summarized in Table 16. No statistical tests were considered necessary because the results can be interpreted by inspection. In the control Table 16 A summary of perch use data for the four chipmunks used in the 1968 experiment enclosure. Data represent the number of times the chipmunks used the elevated perch in a pen. 69 Treatments Low Perch Hifth Perch Open Pens Control 36.97 31.33 Horizontal Restrictions 17.13 44.18 Vertical Restrictions 28.27 27.60 70 pens and those having vertical restrictions, chipmunks generally used the low and high perches about an equal amount. The high perches in those pens having horizontal restrictions were used considerably more than the low perches in these treated pens. These data indicate a preference by the chipmunks for access to good horizontal visibility. Data obtained from preliminary experimental work agreed with these results. DISCUSSION AND CONCLUSIONS In recent years considerable evidence has been presented and reviewed to support the concept that inter and intraspecific social interaction has a regulatory effect on population size and the physical condition of the individual animals (Calhoun, 1963; Terraan, 1963; Wynne-JSdwards, 1962). Various authors (Crowcraft and Howe, 1962; Healey, 1967; Lorenz, 1966; Tinbergen, 1939) have presented data which implicates aggression and social structure with dispersal and individual spatial distribution of animals, as part of a complex, interacting system. The means by which the social contact is implemented varies from species to species* In birds it is generally conceded that sound and visual stimuli provide the method of contact between members of a population. suggested for various non-human primates. various types of body secretions. These methods are also Other mammals make use of The function of these and other types of stimuli are discussed by Marler and Hamilton (1966). It is suggested that social communication would eventually initiate some type of psychophysiological mechanism which would set limits to the size of the home range and therefore, also population levels. Bronson (1961) demonstrated experimentally and in the field that the visual signal system was the stimulus regulating the agonistic behavior of woodchucks (Marmota monax). This behavior in turn affected the spatial distribution of the members of the woodchuck population. He also postulated some inter­ acting physiological mechanism associated with the adreno-cortical system which resulted in some type of stress factor. 71 Christian (1959* i960, 1961) 72 has described many experiments implicating this system. Thiessen (196*0 reviewed the literature concerning the association of the endocrine system to social and reproductive behavior. Welch (1965) reviewed certain theoretical aspects involving the hypothalamic-reticular system and what he called the Mean Level of Environmental Stimulation. In sum­ mary, there appears to be ample evidence from the literature to support the theory that social contact mediated at various levels of the nervous system could have a significant influence on the neurological, endocrine, behavioral and physiological (£.g. gamete production, vigor of parents and juveniles or both) responses. The level of tolerance to social encounters varies considerably from those animals who are definitely territorial to those who tolerate widely overlapping home ranges. Here again the tolerance level will vary with the season, age, sex and social position of the animal. Jenkins (1961 a) reported that the spatial distribution of partridge Perdix perdix, was correlated with the degree of visual interaction, population density and the density of ground cover. Increasing amounts of interaction as a result of poor cover (extensive horizontal visibility) and higher animal densities or both, resulted in home ranges which were larger and overlapping. Birds in good cover had less visual interaction with each other even at a high population density. In a latter paper (Jenkins, I96I b) he associated a high degree of interaction (as well as the quality of other visual cues) with a lowered degree of physiological resistance to environmental hazards in parental birds and their offspring. My data and that of other authors (Sheppard, 1965; Martinsen, 1965) indicate that the adult chipmunk, with some exceptions, generally maintains 73 the same home range and that it is usually separate from that of other adults. Exceptions to this could he temporary congregations at preferred food locations. A separate home range implies a method exists which can function to disperse and space the individuals, especially the breeding pairs. Visual communication is considered a form of advertised occupancy of a home range. It could serve as a way by which the habitat is partition­ ed through social interaction for a more effective use of social space (Wynne-Edwards, 1962). A void in a formerly active portion of the communi­ cation system could be the signal for a juvenile or neighboring adult to explore the vacancy. Here factors such as access* social dominance, aggression and population density, may determine which, if any, animal fills the vacancy. A home range and a method by which it can be adver­ tised, especially during the breeding season, are behavioral features and therefore should have selective value. The data suggest that poor hori­ zontal visibility would offer few opportunities for visual social encoun­ ters. Thus, home ranges with this type of visibility may be inadequate to attract and hold a mate or provide the necessary visual stimulation to initiate or enhance reproductive behavior or both. These home ranges would be marginal to sub-marginal, end would not provide a consistent breeding population. this type of habitat. Juvenile and sub-adult animals would probably occupy They would provide the reserve for filling optimal home ranges vacated by adults due to death or other factors. Marginal home ranges might be occupied when unusually good reproductive survival resulted in dispersal from high population densities in optimum habitats. The field and experimental data supported the significance of horizontal visibility to habitat selection by the animal. The species' widespread distribution implies an ecologically adaptable animal. Regardless of the apparently diverse habitats it occupies, all species within the genus* are found in open areas which could offer adequate horizontal visibility. This adds further credibility to the hypothesis that this is a basic characteristic of the genus* habitat selection. Field data also implicate brush pile density as being important. It appears that in an environment with a favorable supply of resour­ ces, where the possibility of visual assessment for ''intruding" adults is readily available but that actual visual contact is minimal, the home range tends to be smaller and population density greater. approach this situation most closely. Areas I and II For the latter area only V*# of the total portion was inhabited but it had the highest adult density (3*7 anim­ als per acre). This habitat was typified by the "open" area having good horizontal visibility. However, one small portion with medium horizon­ tal visibility did not support an adult home range. This may have been due to inadequate habitat factors not measured or recognized, its visual isolation from the rest of the population or both* Conversely, a habi­ tat with less restrictive horizontal visibility may provide too many visual social encounters and thus result in a polarizing effect on neighboring animals. This situation would favor larger home ranges which would result in greater dispersal. Thus, breeding season encounters would be reduced to a "tolerable" level (Areas III and V). In Area V, adult animals were so spaced that 6596 of the area was being occupied but by a relatively less dense population (2.1 adults per acre). This area provid­ ed relatively unimpeded vision from those locations where the horizontal visibility was adequate. Thus, distribution of sound and sight stimuli ♦The exception is E. townsendii. 75 would be transmitted maximally. If only subminimal opportunities for visual assessment in the environment prevail, very low or no breeding pairs may be present. This situation may have been present in Area IV which apparently did not have a breeding pair in 196? or 1968. This may also explain why Manville (1949) only trapped 46 E. minimus (includ­ ing recaptures) over a three year period (705 trap-days) on four, 2 acre plots* of what I would consider atypical habitat. In comparison, for Area I only (5.3 acres), I captured 19 animals a total of 90 times dur­ ing 522 trap-days. optimum. His data suggest that the habitats sampled were not Some areas on which I conducted preliminary trapping were similar to those studied by Manville, however, I captured no chipmunks. Greatly restricted horizontal visibility could not afford a chipmunk an opportunity to visually evaluate the number and social status of its neighbors and thus, the likelihood of more direct confrontations (chasing and other acts of agonistic behavior) would increase. If these social contacts reached a certain level per unit of time, changes in the nervous and endocrine systems may be forthcoming. These could initiate animal dispersal and individual spacing as an alternate to more drastic physio­ logical changes associated with a high mean level of visual interaction. E. minimus being a social animal, may require a certain minimal level of social encounters. Lack of them could result in sensory deprivation. Welch (1964) proposed that stress with decreased adrenal function wan a result of a social animal's isolation. Stress with increased adrenal function resulted from sensory overloading and overpopulation. Habitats providing a balance of visual interaction would be considered optimum. Therefore, a maximum breeding population density could be assumed to *SAF types 6, 12, 24, 23. 76 develop in habitats where (1) the sum total of resources including all visual cues, indicated to an animal that the habitat is "habitable". (2) the number of social encounters is adequate to maintain communication but not so frequent or dominating as to produce a stressful situation which would result in dispersal or such a restricted home range that it wasn't a functional breeding unit. Since natural selection normally favors higher levels of organization, psychophysiological mechanisms could be serving as a feedback for population dispersal and stability. These assumptions would not preclude an animal's utilization of special food supplies temporarily in areas of very low or very high horizontal visibility. I have concluded from field and/or experimental data that horizontal visibility and brush pile density are significant environmental factors associated with habitat selection of E. minimus neglectus. I have also suggested their significance to the spacing and density of the animals. LITERATURE CITED Allee, W. C., A. E. Emerson, 0. Park, T. Park and K. P. Schmidt. 19*+9* Principles of animal ecology. W. B. Saunders, Philadelphia. 837 pp. Allen, Durwood L. 19**3. Michigan Fox Squirrel management. Dept., Game Div. Pub. 100. *+0*f pp. Anunann, G. A. 1957. The prairie grouse of Michigan. Game Div. Tech. Bui. 200 pp. Anderson, R. L. 19*+6. Banasiak, C. F. 196*+. Game Div. Bull 6. Missing plot techniques. Deer in Maine. 163 pp. Mich. Cons. Mich. Cons. Dept., Biometrics 2:*+2-*+7. Maine Dept. Inld. Fish Game, Behrend, D. F. 1966. 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Utah State Univ. 58 PPMayr, E. 1963* Animal species and evolution. Cambridge, Mass. 797 pp. Harvard Univ. Press, Miller, A. H. 1942. Habitat selection among higher vertebrates and its relation to intraspecific variation. Amer. Naturalist 76:25-35. Miller, A. H. 1944. Specific differences in the call notes of chip­ munks. J. Mammal. 24:87-89. Mohr, Carl 0. and W. A. Stumpf. 1966. Comparison of methods for cal­ culating areas of animal activity.J. Wildl. Mgmt. 30:293-303. Moody, P. A. 1929. Brightness vision in the deer mouse Permyscus maniculatus gracilis. J. Exptl. Zool. 52:367-405Odum, Eugene P. 1959. Phil. 546 pp. Fundamentals of ecology. W. B. Saunders Co., Ogilvie, D. M. 8c R. H. Stinson. 1966. Temperature selection in Peromyscus and healthy laboratory mice, Mus. museulus. J. 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J. Wildl. Mgmt. 32:566-57*+• Walker, R. E. 196*+. An experimental investigation of habitat selection by woodland mice. M. A. Thesis. Univ. of Toronto. *+6 pp. Wecker, Stanley C. 1963. The role of early experience in habitat selection by the prairie deermouse, Peromyscus manicuiatus bairdi. Ecol. Mono. 33:307-325. Welch, B. L. 1965. PsychophyBiological response to the mean level of environmental stimulation: a theory of environmental integration, pp. 39-99* Symposium on Medical Aspects of Stress in the Military Climate. U. S. Govnt. Prtg. Office. 1965: 778-81*+. Whitaker, John O. Jr. 1967. Habitat relationships of four species of mice in Vigo County, Indiana. Ecology. *+8:867-872. Wolfe, James L. 1968. Average distance between successive captures as a home range index for Peromyscus leucopus. J. Mammal. *+9:3*+2-3*+3. Wynne-Edwards, V. C. 1962. Animal dispersion in relation to social behavior. Oliver and Boyd, Edinburgh and London. p. 653. APPENDIX Figure 9 Schematic of miniaturized transmitter 63 ^CRYSTAL T _ Cl COLLECTOR ANTENNA MITTER R2 Rl BATTERY 84 Table 17. Animal Number 1 a 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 E L T * Age, sex and weight data obtained from Area I, 1965 and 1966. Sex Female Male Female Female Female Male Male Male Female Male Male Female Male Male Female Male Male Female Female Estimated Age A A A A A A A A A(sub) J J J J A(sub) J J J J J enlarged teats lactating enlarged testes in breeding condition in spring 1966 Weight in Grams 40 36 44 42 **5 34 38 39 40 28 29 30 29 38 31 20 30 32 31 Reproductive Condition L T E E E T T (died 7/3/65 T Neg Neg Neg Neg Neg Neg* Neg Neg NegCdied 7/19/65 Neg Neg 85 Table l8. Age, sex and weight data obtained from Area II, 1965* Animal Estimated Weight Reproductive Number________Sex_________Age__________ in Grains________ Condition 1 2 3 b 3 6 7 8 9 10 11 12 13 lb 15 16 17 E L T Male Male Male Male Female Female Male Female Female Female Female Male Male Male Male Male Female enlarged teats lactating enlarged testes A A A A(sub) A A J A J J J J J J J A J 35 38 38 32 bi b2 30 *+l 31 35 37 29 30 28 32 bo 3k T T T Neg E E Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Table 19Inimal lumber 1 2 3 4 5 6 7 8 9 10 11 12 13 E Age, sex and weight data obtained from Area 111, 196?. Sex Female Male Male Female Male Female Male Female Male Female Female Female Male enlarged teats Estimated Age J J A A A J A J J J J A J Weight In Grams 35 30 39 k7 kl 36 39 35 32 35 36 30 Reproductive Condition Neg Neg Neg E Neg Neg Neg Neg Neg Neg Neg E dead in trap Neg 87 Table 20. Age, sex and weight data obtained from Area V, 1968. Animal Number Sex 1 2 3 4 5 6 7 8 9 Male Male Female Male Female Male Female Female Male E T enlarged teats enlarged testes Estimated Age A A A A A A A A A Weight in Grams 38 39 43 38 44 33 44 46 36 Reproduc tive Condition T T E T E T E E Testes Regressing 88 Table 21. Trapping effort and success for Area II, 1966.* CAPTURE DATES Chipmunk Number and _______ Age______ May 1 2 3 4 5 6 7 9 10 11 12 13 14 15 16 * A A A A A J J J J J J J J A J une X X X X X X X X XX X J uly____ August____ Sept.______ Totals X X X X XX X X X X X X X X X X X X X XX X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Ninety traps set each trapping day except 20 in May. 6 7 6 4 3 2 4 4 4 3 5 4 4 4 2 89 Table 22. Trapping effort and success for Area III, 196?* CAPTURE. DATES __________________________________ August________________ Chipmunk Number and Age 21 27 X 28 1 J X 2 J X 3 A X A X 5 A X 6 J X 7 A X 8 J X 9 J X 10 J X 11 J X 12 A X 13 J 29 30 Totals 2 1 X X 3 X 2 X X 2 X 3 1 X 2 2 X X 2 X 2 1 X * Thirty-six traps set Aug. 21, 153 Aug. 29, other days 15^• 1 90 Table 23. Trapping effort and success for Area IV, 1967 and 1968. CAPTURE DATES September, 1967 Chipmunk Number and Age 2 1 A X 2 A X 3 k X Totals 2 1 June, 1968 2______ ^ _______ ft 1 X X 2 91 Table 2k. Trapping effort and success for Area V, 1968. CAPTURE DATES Chipmunk Number and April* 17 19 20 May* 21 X 3 if June* 6 1 2 ? if Totals 5 2 X 1 A 2 A X 3 A X if A 5 X X X X X X X X A X X 6 A X 7 A X 8 A X 9 A X X X 5 X 5 if X X * One hundred and fifty-six traps set. 6 X X X X X X X if X if X 2 X 1 92 Table 25. Animal 1 2 3 if 5 6 7 8 9 10 11 12 13 14 13 16 17 18 19 Averages A summary of movement and home range data from 1963 and 1966 for Area 1. Number of 8 10 8 7 6 11 5 10 4 6 6 5 7 if 3 3 3 2 2 5.7 Number of Times Home Range Size (in acres! Farthest Movement Recorded (feet) — — - - 178 312 223 267 223 267 235 312 314 310 401 403 322 309 243 356 378 200 343 .67 295 2 1 1 2 1 2 2 2 1 2 1 3 1 — 2 1.6 .44 .96 .63 .48 .41 .59 .52 .7*+ .67 .89 .55 1.14 .81 .44 .63 — .89 93 A summary of movement and home range data, 1965, Area II. ■ of Trapped Number of Times Seen per Visit 6 7 6 4 5 2 4 2 5 4 4 4 4 2 4 3 1 2 2 2 1 1 2 2 1 1 2 3 1 1 2 1 - 3.9 1.6 Home Range Size (in acres) .57 .70 .42 .29 .40 .6? .31 .31 .70 .86 1.40 .46 .14 .41 .31 — 233 250 240 .53 257 16? 208 24 1 183 250 333 284 433 330 217 300 167 9*+ Table Anima Nmnbe, 1 2 3 4 5 6 7 8 9 10 11 12 13 Movement and home range data for Area III* 196? • Number of Times Trapped Number of Times Home Range Seen per Visit_____ Size____ (in acres) 2 2 .68 1 3 2 1.18 1.95 2 — .86 2 2 3 1 1.64 1.27 .31 .31 .45 .50 3 1 2 2 2 2 1 2 2 2 2 1 1 1 1.8 1.8 - .91 95 Table 28. Animal Number 1 2 3 if 5 6 7 8 9 Averages Movement and home range data for Area V, 1968. Number of Times Trapped Number of Times Seen per Visit 2 5 5 5 3 3 3 2 1 5 k 1 if 2 3 1 3.2 2.6 1 Home Range Size (in acres) Farthest Movement Recorded (feet) l.lif 1.20 .36 1.60 *^3 .6it •36 - if69 575 173 600 250 230 198 156 250 .81 522 96 Table 29. Season Spring prior to July 1 Summer July 1 to Sept. 10 Fall After Sept. IO Totals Distribution of the new animals captured for each trapping period.* They are categorized into either spring, summer or fall periods to reflect recruitment into the population from natality and/or dispersal. Areas III Trapping periods* I 1 7 2 1 3 - 3 O 3 - 1 1 7 6 2 3 2 4 2 3 5 1 2 k 1 0 1 l l 1 19 17 11 13 IV V New animals marked in each period Accumulatin percentage total anime marked 6 16 .22 - 2 7 .32 - 1 5 .39 16 .62 - 13 .80 0 - 8 .93 0 - 2 .96 2 1.00 2 9 1.00 * A trapping period may be one out of a series of consecutive or nearly consecutive days, or a compilation of nearly consecutive days. Table 30. A summary of chipmunk densities for all areas. Estimated Density of Adult Animals per Acre Estimated Overall Density per Acre Total Size in Acres Known Number of Adults on Area* I 5.3 8 1.5 19 3.6 II 4.2 7 1.7 17 4.0 III 6.2 5 .8 15** 2.4 Irea Total Number of Animals 'm IV 2.5 2 .8 2 .8 V 6.6 9 1.4 9 1.4 * ** This includes some animals that may be transient to an area. This includes two unmarked animals seen on the area after trapping and marking operations were concluded. 98 Table 31. Animal Number Telemetry data for Area III. Number of location points determined by telemetry Total distance tracked via telemetry in feet Life of transmitter 1 26 44o 4 days 2 18 340 ? 3 33 940 3 days 4 29 560 6 days 5 26 460 3 days 6 29 350 4 days AREA I ^ ^<3© ^ -I-- & OUTLI NE RANGES ] O F COMBINED E S T I M A T E D FOR A L L ANIMALS- HOME O U T L I N E O F COMBINED E S T I M A T E D R A N G E S FOR A D U L T S ONLY- HOME OUTLINE RANGES HOME O F COMBINED E S T I M A T E D FOR J U V E N IL E S . SHADED PO R TIO N S O F T H E A R E A WERE RATED A S HAVING P O O R H O R I Z O N T A L V I S I B I L I T Y ; U N S H A D E D , MEDIUM T O G O O D . OUTLI NE RANGES O F COMBINED E S T I M A T E D FO R A L L ANIMALS- O U T L I N E O F COMBINED E S T I M A T E D RANGES FOR A D U L T S ONL Y. O U T L I N E O F COMBINED E S T I M A T E D R A N G E S FOR J U V E N I L E S . HOME HOME HOME SHADED PORTIONS O F T H E AREA WERE RATED A S HAVING P O O R H O R I Z O N T A L V I S I B I L I T Y ; U N S H A D E D , MEDIUM t o g o o d . A R K A II 100 N _ ’ OUTLINE RANGES O F COMBINED E S T I M A T E D FO R A L L ANIMALS- HOME O U T L I N E O F COMBINED E S T I M A T E D H OM E R A N G E S FOR A D U L T S ONLYO U T L I N E O F COMBINED E S T I M A T E D H O M E R A N G E S F OR J U V E N I L E S . - . S H A D E D P O R T I O N S O F T H E A R E A WERE : RATED A S HAVING P O O R H O R I Z O N T A L V ISIB IL IT Y ; u n s h a d e d , m ed iu m t o g o o d . 100 N _____________ OUTLINE RANGES O F COMBINED E S T I M A T E D F O R A L L ANI MAL S - HOME ________ ____O U T L I N E O F COMBINED E S T I M A T E D HOME R A N G E S FOR A D U L T S ONLY. ___ O U T L I N E O F COMBINED E S T I M A T E D HOME R A N G E S FOR J U V E N I L E S . S H A D E D P O R T I O N S O F T H E A R E A WERE __________ I RATED A S HAVING P O O R H OR I Z ON T AL VISIBILITY; UNSHADED, MEDIUM TO G O O D . AREA III 101 OUTLINE RANGES O F COMBINED E S T I M A T E D FO R A L L ANIMALS- _ O U T L I N E O F C OM B I N ED E S T I M A T E D RANGES FOR A D U L T S O N L Y . O U T L IN E O F COMBINED E S T I M A T E D RANGES FOR JU V E N IL E S . HOME HOME HOME S H A D E D P O R T IO N S O F T H E A R E A WERE j R A T E D A S H AVI NG P O O R H O R I Z O N T A L V I S I B I L I T Y ; U N S H A D E D , m e d iu m t o G O O D . ■5 101 scale _____________OUTLI NE RANGES 1-12 5 O F COMBINED E S T I M A T E D FOR A L L ANIMALS- HOME ________ ____O U T L I N E O F COMBINED E S T I M A T E D HOME RANGES FOR A D U L T S ONLY . O U T L IN E O F COMBINED E S T I M A T E D HOME ---------------- R A N G E S FOR J U V E N I L E S . r ----------— i S H A D E D 1 P O R T IO N S O F T H E AREA WERE ] RATED A S HAVING P O O R H O R I Z O N T A L v i s i b i l i t y ; u n s h a d e d , medium t o g o o d . AREA IV 103 w scolo ' l'V 100 OUTLINE RANGES O F COMBINED E S T I M A T E D FOR A L L ANIMALS- HOME , O U T L I N E O F COMBINED E S T I M A T E D H O ME R A N G E S FOR A D U L T S ONLYO U T L I N E O F C OMB INED E S T I M A T E D H O ME R A N G E S FOR J U V E N I L E S . SHADED PO R TIO N S O F T H E AREA WERE RATED A S HAVING P O O R H O R I Z O N T A L V I S I B I L I T Y ; U N S H A D E D , MEDIUM T O G O O D - OUTLINE RANGES O F COMBINED E S T I M A T E D F O R A L L ANI MAL S - H O ME O U T L I N E O F COMBINED E S T I M A T E D HOME R A N G E S FOR A D U L T S ONLYO U T L I N E O F COMBINED E S T I M A T E D HOME R A N G E S FOR J U V E N I L E S . C ,, S H A D E D P O R T I O N S O F T H E A R E A W E R E R A T ED A S HAVING P O O R H O R I Z O N T A L V I S I B I L I T Y ; U NS H A D E D , MEDIUM T O G O O D . AREA V OUTLINE RANGES O F COMBINED E S T I M A T E D FO R A L L ANIMALS O U T L I N E O F COMBINED E S T I M A T E D RANGES FOR A D U L T S ONLYO U T L IN E O F COMBINED E S T I M A T E D RANGES FOR JU V E N IL E S . HOME HOME HOME SHADED PO RTIO N S O F T H E AREA WERE RATED A S HAVING P O O R H O R IZ O N T A L V I S I B I L I T Y ; U N S H A D E D , MEDIUM T O G O O D - 103 M OUTLINE “ RANGES O F COMBINED E S T I M A T E D FO R A L L ANIMALS- _ O U T L I N E O F COMBINED E S T I M A T E D RANGES FOR A D U L T S O N LY O U T L IN E O F COMBINED E S T I M A T E D RANGES FOR JU V E N IL E S . HOME HOME HOME -i S H A D E D P O R T I O N S O F T H E A R E A W E R E 1 RATED A S HAVING P O O R H O R I Z O N T A L v i s i b i l i t y ; u n s h a d e d , m edium t o g o o d . 104 Tables 32 through 40 summarize, in logarithmic form, the data obtained by measuring the time spent in the various pens exposed to different treatments. The data were collected from the 1968 experimental enclosure. Table 32. Comparison of the treatments perch height and vertical visibility. No Vertical Vertical Totals 16" Perch 24" Perch 107.10 122.60 91.23 94.02 198.33 216.62 Totals 229.70 185.25 414.95 Table 33- Comparison of the treatments perch height with chipmunks. Chipmunk 16" Perch 24" Perch Totals 2 3 4 5 59.02 54.21 33.23 49.81 65.18 55.51 48.26 47.87 124.20 109.52 83.49 97.74 198.33 216.62 414.95 Totals Table 34. Comparison of the treatment horizontal visibility with chipmunks. Chipmunk No Horizontal Horizontal Totals 2 3 4 5 72.98 66.10 55.03 60.13 51.22 43.42 28.46 37.61 124.20 109.52 83.49 97.74 254.24 160.71 414.95 Totals Table 35Chipmunk 2 3 4 5 Totals Comparison of the treatment horizontal visibility with chipmunks. Vertical Totals 66.01 62.37 43.94 57.38 58.19 47.15 39.55 40.36 124.20 109.52 83.49 97.74 229.70 185.25 414.95 No Vertical 105 Table 56. Comparison between the treatments perch height and horizontal visibility with chipmunks. Chipmunk 16" Perch No Horizontal Horizontal 2 3 it 5 Totals Table 37. Chipmunk Totals Table! 38 Chipmunk 24.84 17.89 7.21 16.76 38.80 29.78 27.01 27.02 26.38 25.53 21.25 20.85 124.20 109.52 83.49 97.74 131.63 66.70 121.61 94.01 414.95 Comparison between the vertical visibility and horizontal visibility with chipmunks. Totals Table 39. Totals * Totals 24.95 22.34 14.56 19.06 31.92 26.07 25.65 21.81 26.27 21.08 13.90 18.55 124.20 109.52 83.49 97.74 148.79 80.91 105.45 79.80 414.95 Comparison between the vertical visibility and perch height with chipmunks. 24" Perch No Vertical Vertical Totals 31.70 30.34 17.88 27.18 27.32 23.87 17.35 22.69 34.31 32.03 26.06 30.20 30.87 23.28 22.20 17.67 124.20 109.52 83.49 97.74 107.10 91.23 122.60 185.25 414.95 Comparison between the perch height, horizontal visibility and vertical visibility No Vertical No Horizontal Horizontal 16" Perch 24" Perch Vertical No Horizontal Horizontal 4i.6o 40.03 29.38 38.32 16" Perch No Vertical Vertical 2 3 4 5 Totals 34.18 36.32 28.02 33.11 No Vertical No Horizontal Horizontal 2 3 4 5 24" Perch No Horizontal Horizontal Vertical No Horizontal Horizontal Totals 75.84 72.95 31.26 49.65 55.79 49.66 35.44 44.36 198.33 216.62 148.79 80.91 105.45 79.80 414.95 106 Table 40. Comparison between the perch height, horizontal and vertical visibility with chipmunks. Chipmunk 2 H V P (1) HV PV PH PHV Totals Chipmunk 3 Chipmunk 4 Chipmunk 5 Totals 10.99 13. **7 20.35 20.71 13.85 18.*+5 13.96 12 .*+2 9.26 15.24 18.95 21.08 8.63 10.83 13.08 12.45 2.71 12.85 14.21 15.17 4.50 12.80 11.85 9.40 8.30 14.23 19.44 18.88 8.46 7.58 10.76 10.09 31.26 55-79 77.95 75.84 35.44 49.66 49.65 44.36 506.65 409.83 339.13 338.09 1593.71 107 Tables 4l and 42 summarize in logarithmic form the data obtained by measuring the time spent in the various pens exposed to different treatments. The data were collected from the 1968 experimental enclosure. Table 4-1. Comparison of the treatment vertical visibility with that of horizontal visibility « No Vertical Vertical Total No Horizontal 48.79 105.45 254.24 Horizontal 80.91 79.80 160.71 229.70 185.25 4l4.95 Total Table 42. Comparison of the treatment perch height witl that of horizontal visibility. No Horizontal Horizontal Total l6H Perch 131.63 66.70 198.33 24" Perch 122.61 94.01 216.62 Total 254.24 160.71 414.95 108 Tables 43 through 45. The number of times the chipmunks used the elevated perch in a pen. Refer to the text for a description of the experimental treatments. Data obtained from the 1968 experimental enclosure. Table 43* Treatment Open. Chipmunk 16" Perch 24" Perch Total 2 3 4 5 5-24 10.12 9.93 11.68 7.22 11.08 10.09 2.99 12.46 21.60 20.02 14.6? 36.97 31.33 68.40 Total Table 44. Treatments Horizontal. Chipmunk 16" Perch 24" Perch Total 2 3 4 5 3.94 6.23 1.79 5.19 10.46 10.07 12.23 11.42 14.90 16.30 14.02 l6.6l 17.15 44.18 61.83 2*1" Perch Total Total Table 45. Treatments Vertical. Chipmunk 2 3 4 5 Total 16" Perch 3.68 9.46 6.89 8.24 3.25 8.57 8.97 6.81 6.93 18.03 15.86 15.05 28.27 27.60 55.87