' - '0- 7.”... a to II . v "'_'.", f. I... '. -o.o-o'¢ u c to f‘f'l”. — r .. . -(. 0-..1 . 4...-.. ¢.¢o on J...’ a-opoovo-o- , . -_, "£6! . I J "l " 0- .._ ... C.- O a J. '4 AN ECOLOGICAL STUDY (3?"- THERED FOX IN THE EAST-CENTRAL UPPER PENINSULA OFMECHEGAN Thesis for the Degree of M. S. MiCHlGAN STATE UNNERSITY Robert Samuei Huff 1964 . - nnnnn u THESIS LIBRARY Michigan State University M!IllllllflzllfljflllltlflujflmmlfiW12!!! PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. MTE DUE DATE DUE 1b'r' 4“ 3"! 1%! 0 1 out; 032304 | io-‘I’ C 1M chlHCDdoOuopOS—p.“ ABSTRACT AN ECOLOGICAL STUDY OF THE RED FOX IN THE EAST-CENTRAL UPPER PENINSULA OF MICHIGAN by Robert Samuel Huff Ecological data on the red fox were collected in the east-central portion of the Upper Peninsula of Michigan to determine its actual pre- dation and effects on game species, its habitat preferences, its be- havior, and its winter food habits. Behavior and activities of foxes were studied by following fox trails 98.4 miles in the snow and interpreting animal signs along the trails. Fifty-eight fecal groups and forty-two stomachs were collected and analyzed for food items. Foxes were separated into age classes by using cranial characteristics. Reproductive tracts were analyzed for litter size and breeding seasons. The peak of the breeding season is February to mid March. Average litter size is 4.6 with average ovulation rate of 5.6. Foxes tend to be nocturnal in habit, although some diurnal travel was noted. Mbst foxes traveled alone; groups of more than two foxes traveling together are uncommon in winter. They tended to meander about, visiting a variety of cover types in their nightly travels. Areas with several interspersed cover types are preferred. Extensive areas of hardwoods and conifers were generally avoided. Foxes used the vegetation types in approximately the same proportion as the types Robert Samuel Huff occurred. Some preference was shown for small coniferous swamps, semi- open and mixed hardwood-conifer types. Rhee and voles occurred in the foxes diet with the highest fre- quency of occurrence in the winter months. They also ranked second in total volume. White-tailed deer shot and wasted by hunters constituted the greatest volume of winter foods. Snowshoe hares were also prominent in the winter diets. Insectivores were commonly discarded by foxes, however, they occurred with a surprisingly high frequency in the stomach analysis. Ruffed grouse occurred in minor amounts in both stomachs and seats. A variety of small mammals rounded out the winter diet. Effects on small game species appeared negligible. AN ECOLOGICAL STUDY OF THE RED FOX IN THE EAST-CENTRAL UPPER PENINSULA OF MICHIGAN BY Robert Samuel Huff A THESIS Submitted to iMichigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Fisheries and Wildlife 7% 1964 -/ ACKNOWLEDGMENTS The field investigations covered in this report were conducted in cooperation with the Game Division of the Midhigan Department of Conservation. I thank Mr. H. D. Ruhl, Chief of the Game Division, for making this study possible. I am especially grateful to the late Dr. Stanley Whitlock and David Arnold for initiating the study. D. F. Switzenberg, Biologist in charge of the Cusino Wildlife Experiment Station supplied laboratory and office space and offered valuable advice in carrying on my field work. Other personnel at the Game Division extended services in various ways. Dr. L. D. Fay and W. C. Ybuatt made the facilities at the Game Division laboratory available for the laboratory work. I wish to thank Loyd Schemenauer for his interest and aid in collecting specimens. Dr. C. T. Black kindly edited the manuscript. Appreciation is expressed to Doctors Rollin Baker and Miles Pirnie for their helpful editing and constructive criticisms. iMuch gratitude is expressed to Dr. Leslie Gysel for his guidance of my program at Michigan State University and for editing the manu- script. Finally, I am very grateful to my parents and my wife Ermine, for their assistance and constant encouragement. ii TABLE OF CONTENTS INTRODUCTION STUDY AREA 0 O O O O I O O O O 0 METHODS AND SCOPE . . . . . . . . RESULTS 0 O O O O O O O O O O O 0 DESCRIPTION AND DISTRIBUTION OF THE RED FOX FOX SIGNS REPRODUCTION . . . . . . . . . AGE DEIERMNATION O O O O O O MOVEMENT OF RED FOX . . . . . Travel Reactions to Weather Reaction to Man's Activities Dens, Beds, and Resting Places open-0000000000 Semi-open Upland Hardwoods . . . Mixed Hardwood-Conifer . Coniferous Swamp . . . . Other Vegetation Types . SMIMJBEHAVIOROOOOOO. FOOD HABITS . . . . . . . . . Food Availability . . . . . Manner of Hunting . . . . . Storage Habits . . . . . . Winter Foods by Species . . Mice and Voles . . . . . Snowshoe Hares and Cotton Deer.......... Porcupine . . . . . . . Moles and Shrews . . . . Squirrels . . . . . . . Domestic Animals . . . . Woodchuck . . . . . . . BirdSooooooooo Vegetable Matter . . . . Inedible Material . . . FOXoooooooooo SWY O O O O O O O O O O O O 0 LITERATURE CITED tai g..- 51 H0 e b t O O O Q 0 O Page 10 10 ll l4 17 20 22 23 25 30 34 37 38 39 39 4O 41 43 45 49 49 49 55 56 57 60 61 61 61 62 64 65 65 66 7O LIST OF TABLES Table Page 1. Winter habitat use by red foxes during 98.4 miles of tracking in central Upper Peninsula of Michigan - 1955 O O O O C O O O C O O O O O O O O O O O C O O O O 32 2. Habitat availability as determined from 2,560 acres considered most representative of the study area, and fox use during 98.4 miles of tracking . . . . . . . 34 3. Winter hunting and feeding activities of red fox as determined by 98.4 miles of tracking in central and eastern Upper Peninsula - 1955 . . . . . . . . . . . 35 4. Winter foods of red fox in central Upper Peninsula determined from analyzing 58 seats collected in Winter 1 955 O O O O O O O O O O O O O O ' O O C i O O O O 0 50 5. Winter food habits of red fox as determined by field observations along 98.4 miles of trails in east central Upper Peninsula - 1955 . . . . . . . . . . . . . 52 6. Winter food habits of red fox as determined by field observations of Department of Conservation personnel while tracking foxes 25.5 miles in central Upper Peninsula 1952-54 . . . . . . . . . . . . 53 7. Winter foods of red fox determined from analyses of 42 fox stomachs collected in east central Upper Peninsula in winter of 1955 . . . . . . . . . . . 54 iv LIST OF FIGURES 1. Tracks of bounding fox . . . . . . . . . . . . . . . 2. Reproductive tract showing four developing embryos; female killed February 9, 1955. E1 through E4 arefourembryos ................ 3. Foxes made deep openings in snow to keep dens open . 4. Deeply indented entrance path to den indicating constant winter use . . . . . . . . . . . . . . . 5. Fox bed located on knoll . . . . . . . . . . . . . . 6. The observed frequency of occurrence of fox trails in distance categories within vegetation types . 7. Cover map of 2,560 acres considered most typical of theatUdyareaooooooooooooooooo 8. Tracks of red fox hunting small rodents. Note. investigation.of stumps and other places of possible food . . . . . . . . . . . . . . . . . . 9. Porcupine carcass "skinned" by red foxes . . . . . . Page l3 16 26 27 29 31 33 47 59 INTRODUCTION The red fox (Vulpes fulva) as a predator has long been a con- troversial subject in.Michigan. Its status as a predator and its role as a bountied animal has considerable economic significance to the field of conservation. The Department of Conservation, many Sportsman's groups, and individual conservationists feel that the bounty system has not accomplished the objectives for which it was meant and would like to repeal the present bounty. The money thus saved could then be used for other much needed conservation programs. Bounty figures indicate that foxes are at least as abundant today as they were in 1947, the year the present bounty was initiated. The many proponents of the fox bounty maintain that the red fox takes excessive numbers of small game animals in Michigan. Ecological and food habits studies in the pheasant range and in the ruffed grouse range in southern Michigan by Arnold (1956) and Schofield (1959) have somewhat clarified the foxes position in the animal community. Ecological data and food habit information pertaining specifically to the red fox in the Upper Peninsula of Michigan are sparse or lacking. Plant and animal communities there differ somewhat from those found in the southern Michigan studies. Thus I feel that the southern.MHchigan data may not be applicable to the Upper Peninsula. In this study, I collected ecological data on red foxes in the east-central portion of the Upper Peninsula of Michigan during the winter of 1954-55. The objectives were: (1) to determine the actual 1 2 predation of the red fox on species of prey, and attempt to determine the effects on game species numbers; (2) to determine the winter food habits of the red fox; (3) to determine home range, cruising radius, daily movements, and habitat preferences; and (4) to gather as much information as possible concerning predator habits, hunting success, mating dates, reproductive rates, age structure, and other data of in- terest. It is the object of this thesis to report these data so that a clearer picture may be obtained as to the true relationship of the red fox to its environment. STUDY AREA This study was carried on in the east-central portion of the 'Upper Peninsula of Michigan. Field work was carried on in portions of Marquette, Alger, Schoolcraft, and Chippewa counties. Areas in- vestigated were determined by the presence of red fox activities. Many miles were traversed by automobile in search of fox signs. The areas in which the most fox tracks were found thus comprised the most typical description of the study area. These areas were generally loamy sands, sands, and sandy loam soils, varying from level to rolling terrain. The original forest was mainly hardwoods with scattered areas of white pine. A considerable amount of the land had been cleared for agricultural use and then abandoned, thus creating many openings. Small coniferous swamps are scattered throughout the area; almost no hardwood swamps are present. Most of the vegetation consists of second growth hardwoods. Extensive areas of dense coniferous swamp were checked throughout the winter, but these areas generally had few fox signs. The second growth hardwoods are composed mainly of sugar maple (Acer saccharum) beech (Eag2§.grandifolia), and white elm Ulmus american ). White birch (Betula papyrifera) and small-toothed aspen (Populus tremuloides) are found frequently in these areas also. Hemlock (Tsuga canadensis) and balsam fir (Abies balsamifera) frequently occur as associated species in the hardwood types. Densities vary from medium stocking to heavy stocking with diameters averaging up to ten inches. 3 4 Low areas of organic soils with white cedar (Thuja occidentalis), spruce (Pigga_spp.), tamarack (Larix laricina), balsam fir, and black ash (Fraxinus REESE): are scattered throughout the study area. Stocking of these plants is heavy, with a dense overstory in most instances. Semi-open areas support scattered clumps mainly of red maple (Acer rubrumo, trembling aspen and pin cherry (Prunus pennsylvanica). Associated species in this type were juneberry (Amelanchier canadenses), hawthorn, (Craeteaggs spp.), and hazel (Corylus americana). Density was a very light stocking'with diameters of trees seldom exceeding 8-10 inches. The terrain is mostly flat to slightly rolling, inter- spersed with low ridges. Open areas consist of idle fields and pastures under a heavy canopy of snow. Very little vegetation or cover remained above the snow except for occasional single trees, stumps, and tufts of grass. Some grassy areas on wind-swept knolls provide cover for mice. METHODS AND SCOPE Between December 28, 1954, and March 25, 1955, 54 foxes were tracked by the author in the central and eastern portion of the Upper Peninsula of Michigan. During this period 98.4 miles of tracking data were compiled. The mileage was determined by use of a pedometer, and a count was kept of paces, using a Veedor counter. Frequent checks were made under varying conditions of snow depth and consistency, to eliminate as many errors as possible and to obtain the greatest possi- ble accuracy. Taken from the files of the Michigan Department of Conservation are 25.5 miles of additional tracking data. These are records of 29 foxes tracked by game biologists during the years 1952 through 1955. The tracking technique has been used by several investigators in past studies of the larger predatory animals. Marie (1936), Erickson (1955), Arnold (1956), Schofield (1960), and Ozoga (1963) used this method in ecological studies of the red fox, bobcat, and coyote. Stebler (1939) says, "stated simply, the method consists of following the trails left by these mammals and interpreting from the clues they may leave, their activity and behavior." Marie (1936) notes: "It is practically equivalent to observing an animal for a long period of time under natural conditions." Our Upper Peninsula weather provides suitable tracking-snow conditions from late November tO‘mid-April. 6 Arnold (1956) trailed foxes for 1,000 miles in the agricultural areas of southern Michigan to determine their winter food habits. Schofield (1960) trailed foxes for 1,000 miles in the northern half of the Lower Peninsula, primarily to determine the effects of red foxes on ruffed grouse (Bonasa umbellus). In the present study, areas of fox concentrations were found by driving along side roads until a track was found crossing the road. Fox tracks were determined by the size of the track and the character- istic manner of travel (described later under fox sign). Scent posts with an odor peculiar to foxes served to corroborate track evidence. These tracks often lead to dens. Areas of known fox concentrations were visited regularly. Information from local hunters and trappers aided in finding tracks. Several dens were being used through the winter, and these were watched closely. When tracking foxes, the different habitats used were recorded on a tracking record form. The distance traveled in each habitat was recorded to determine preferred habitats. I noted each time a fox passed into a different habitat to determine possible habitat preferences. When the meeting of two or more trails confused the identity of the track being followed, the record of the first trail was ended. A new trail record began.when a single trail could again be distinguished. A later discussion will cover habitat descriptions. The distance from.the point where a fox trail was first encoun- tered to the point where a fox was "jumped" from its daytime bed was recorded to determine the average nighttime or daily travel. A straight line measurement from.the place a fox was jumped to the point where its trail began was used as a radius to determine daily range. 7 The 47 specimens used in this study, were bountied animals taken by hunters and trappers in the general study area, and collected by Michigan Department of Conservation biologists and by me. From these animals 42 stomachs were saved for food analysis. Reproductive organs, skulls and long bones were saved as possible means of determining age, and reproductive data. The winter food habits have been determined mostly from the analyses of materials collected in the winter of 1954-55. In addition, 25.5 miles of fox tracking in the Upper Peninsula by Michigan Department of Conservation personnel between the years 1952-54 are also used to substantiate my findings. I personally followed 98-1/2 miles of tracks. Fifty-eight scat groups and 42 fox stomachs were analyzed. The food found in the stomachs was often in recognizable chunks. The smaller animals, such as squirrels, mice, and shrews, were usually bitten into small chunks. The larger animals, such as deer, rabbits, woodchucks, and porcupines were usually in larger chunks. The stomach contents were washed in sieves of two different sizes. The contents were then separated. It was almost always necessary to make micro- scopic examination of the hair. "Scat" groups were collected in the field. Only "seats" found on fox trails were saved, due to the similarity to bobcat and coyote scats. A total of 58 fox seats were collected while tracking foxes during the period January through April, 1955. The seats were placed in paper bags, labeled as to date, location and any other pertinent information, and dried and stored. I analyzed the fox seats at the Michigan Department of Conserva- tion Game division laboratory at Michigan State University. Identifi- cation of the food items was accomplished by use of a binocular 8 dissecting microscope. The hair was identified by use of a compound 'microscope, with reference to a collection of hair slides and photo- graphs available at the laboratory. The analytical procedure followed closely that of Erickson (1954) and Mosby (1960). All scat materials were examined in the dry state after careful separation of materials. Percentage calculations were then made for frequency of occurrence. Each stomach content, each food item eaten while being tracked, and each scat group, is considered to represent a meal. The food items eaten.while being tracked are listed as number of items, number of attempts, and number of actual kills. The seat groups are tabulated by their frequency of occurrence, by months, and as a total. The stomach contents were tabulated volumetrically and by frequency of occurrence. The volume of the individual foods are important in determining the relation they play as a prey species or as a source of food. Therefore, the contents of the stomachs were tabulated by the per- centage of total volume. In addition, 21 bacula and 22 female reproductive tracts were collected for examination. The bacula were used as one means of aging the male segment of the population using Petrides (1950) method of relative roughness and muscle attachments. The skulls and long bones were saved as a means of determining age from cranial variation as set up by Churcher (1960) and by the closure of the epiphyseal lines of the long bones (Sullivan and Haugen 1956). Twenty-two female reproductive tracts were saved as a means of determining reproduction rates, mating periods, and as a possible means of separating adults from juveniles. Litter size was determined by a count of mature Graafian follicles, corpora lutea, and number of embryos. 9 Breeding dates were determined by noting when females were in oestros. The development and size of the Graafian follicles was also used as an indication of the peak of the breeding season. All food items eaten by foxes in the field were recorded on tracking record forms. Any item eaten was considered food. Only in cases where there was positive evidence of mortality was the item con- sidered as a fox kill. Except in cases of actually finding blood, fur, or other signs in the snow indicating a positive kill, all attempts to capture mice were considered as merely attempts. This probably results in a considerable error, as the small size of mice enables a fox to "bolt" the animal entire, thus leaving no signs of a kill. Carrion was considered as any animal not killed at the time of eating. w DESCRIPTION AND DISTRIBUTION OF THE RED FOX According to Burt (1948), Vulpes fulva is the only species of fox commonly found in the Upper Peninsula of Michigan. There are records of the grey fox (Urocyon cinereoargenteus) in the Upper Peninsula but they are exceedingly rare. (Seton 1925, Burt 1948). Burt (1948) lists records of red foxes in every county in the Upper Peninsula with the exception of Kaweenaw County. The color variations of the red fox are many and varied. Usually the color of the fur is reddish-yellow with a somewhat darker back, black ears, and black legs and feet. The tail is long and full in winter pelage, reddish yellow with some black, and tipped with white. The throat and cheeks are whitish and the belly greyish white. The fur is full and lustrous in winter. The total length is 955-85 mm. (37-38 inches) and the average weight is 10-15 pounds (Burt 1948). The most common variations of the red fox are (1) dark crosses on the withers (cross fox); (2) black, frosted with white hairs (silver fox); and (3) entirely black. Lesser variations of the usual color can consist of many different color shades. All these variations can and have appeared in the same litter (Seton, 1925). The two outstanding color phases collected by the writer were a cross fox and a fox tending toward albinism (eyes were not pink). The red fox skull may be distinguished from the skulls of the 10 11 other carnivores by the following characteristics. The teeth number 42, eleven on each side below and ten on each side above. The last upper molar is smaller than the tooth in front of it. The bony palate ends just in front of the last molar. The parietal ridges usually form a sagittal crest. If present, these ridges are separated at the suture between the frontals and the parietals by a space of less than 10 mm. (more than 10 mm. in Urocyon). The dorsal surfaces of the postorbital processes are slightly concave, forming shallow pits (no pits in Canis). FOX SIGNS When tracks were encountered in the snow the first problem was that of proper identification. The red fox foot print is slightly longer than it is wide, and usually shows nail marks. It is usually about two inches long and not quite as wide. In fresh snow, the track often appears larger, due to the enlargement as the foot goes into and comes out of the track. Good tracking snow on a crust shows four toe pads, the toe nails, and the ball of the foot. The coyote (Qanig latrans), domestic dog (Qanig domestics), bobcat (Lynx rufus), and the common housecat (Eglig domestics) all make tracks similar to that of the red fox; however, there are differences that enable one to dis- tinguish them from fox tracks. The bobcat makes an almost round track, and the nails rarely show. The housecat makes a round track, shows no nail marks, and has a much shorter pace. The coyote and dog tracks are difficult to distinguish from fox tracks except by larger size of the track and the behavior of the animals. 12 The length of the pace of the red fox is usually 12 to 15 inches, and the fox places the hind foot in the track made by the front foot. This leaves a trail that is a comparatively straight line of tracks under normal traveling conditions. When jumped or running hard, the fox makes fairly long leaps, and the pattern changes completely (Fig. l). Rarely does the fox run at a hard pace for more than one-quarter mile unless hard pressed. Foxes often follow other fox trails or previous trails of their own. As they often step exactly in the previous track, it is difficult to determine the number of animals that have passed. However, if a multiple trail is followed for any distance, one will find short ex- cursions branching off from the original trail to investigate various interesting scents and objects. In the snow it is extremely difficult to distinguish differences in tracks of individual foxes. The fairly heavy furred paw and the soft sifting snow tends to prevent distin- guishing individuals by the characteristics of their tracks. In areas of fox concentrations it seems that foxes travel on loosely established routes. Foxes I trailed followed old fox signs for distances up to a mile. Foxes freely use old roads or trails without evidence of recent human usage. There does not seem to be any specific purpose to use them other than for travel lanes. In several cases foxes wandered down unused trails and roads for considerable distances. Plowed roads were usually crossed in a straight line. When obstacles were encountered, the fox usually jumped over them if they were small. However it is common for foxes to jump on top of fallen logs and walk the length of them.before jumping off. When 13 Fig. 1.--Tracks of bounding fox. 14 encountering a fence a fox almost invariable jumps over or through the fence rather than crawling under it. The urine of the red fox is characteristic. The odor of fox urine very closely resembles the odor of skunk musk, but not as intense. The odor is much stronger than that of the coyote scent and serves as another means of distinguishing between tracks of the two animals. The fox, as well as other Canidae, characteristically urinate frequently. urinations for the most part were made on tufts of grass, mounds of snow, stumps or other objects protruding above the snow. In most cases it seemed to be a manner of leaving a scent post as a possible means of identification. I could find no evidence of differences between male and female in manner of urinating. Thus this cannot be used as a means to determine the sex of the animal being tracked. Scent posts were frequently encountered, and rarely did a fox fail to leave its scent. Scent posts seem to have stimulated urination, to leave scent, as many scent posts have been visited by an individual in a very short distance. Fecal deposits were generally found at random spots along the trail. However, it was common to find fecal groups on elevated spots. This may indicate a degree of wariness. In no cases were fecal groups found buried. REPRODUCTION Twenty-two pairs of ovaries and reproductive tracts were collected in this study. These were collected between January and March, 1955, except for one collected in April of that year. Data from these were analyzed to determine litter size, breeding season, ovulation rates, and also used to determine age. 15 Seton (1925) places the breeding season of the red fox in late February or early March. Hamilton (1943) places the breeding period as the month of February in Eastern United States. Asdell (1946) places most breeding dates as late January and February for red fox in general. Richards and Hines (1953) places the mating dates as mid-January until late February in Wisconsin. The breeding season of the northern red fox in this study was determined by the maturation of the Graafian follicles, the condition of the uteri, corpora lutea scars, and approxi- ‘mate age of embryos. The first indication of the breeding season was noted in a fox killed February 5, 1955. The ovaries showed developing Graafian follicles upon dissection. The horns of the uterus were turgid and vascular. This animal had Graafian follicles 5 mm. in diameter. Since the follicles measure 4 mm. diameter 2-3 days before acceptance (Asdell 1946), this places the breeding date of this animal at, or near February 5. All five females in oestrus had turgid uteri. Thus, I believe that this can also be used as a means of determining the breeding season. Ny'data to determine the peak of the breeding season are very limited. Five animals were found to be in oestrus, three between February 5 and February 17, and two on March 5. Ripe follicles were found in all of these specimens. Four embryos were found in a female killed February 9, (Fig. 2) while six embryos were found in an animal killed March 13. A female that had very recently dropped her young was trapped April 18. Two females were just starting to develop follicles on February 28 and March 9. In these two instances, the uterus was not turgid. 16 -..-. s- :~-~ ' ‘ .. Fig. 2.--Reproductive tract showing four developing embryos; female killed February 9, 1955. E1 through E4 are four embryos. 17 From these limited data, it seems that the peak of the breeding season is in February and early March. The specimen with well-developed embryos on February 9, indicates that breeding activity does take place in late January, while the specimens just developing follicles on March 9 indicates that the breeding season probably extends well into 'March. The ovulation rate is based on only eight animals, as these were the only animals showing either corpora lutea or mature Graafian follicles. I have based the ovulation rate on one year only. The average number of mature Graafian follicles was 5.6 with extremes of 4 and 8. The corpora lutea also averaged 5.6 with extremes of 5 and 6. The only two specimens containing embryos averaged 5 embryos each. Accordingly, I have put the ovulation rate at an average of 5.6 with extremes of 4 to 8. Average litter size of 4.5 has been reported by Asdell (1946). Richards and Hines (1953) lists litter size as 5.1 in Wisconsin. Seton (1925) reports general litter size as 4.9. Burt (1948) lists litter sizes as 4.9 in Michigan. Placental scars on one fox showed a litter of 4, whereas two records of embryos show litters of 6 and 4 each. Sheldon (1950) believes that 9 is the average high number but cites many reports of more than 9 in a litter. 0n the basis of the number of corpora lutea and follicle counts, my information does not vary greatly from previous studies. AGE DETERMINATION Criteria for the aging of red foxes are limited. Petrides (1950) l8 classified male foxes as young and adult by using characteristics of the baculum. Churcher (1960) used variations of the cranial character- istics to age and sex red foxes. As the corpora lutea apparently com- pletely regress, there are no scars to indicate previous breeding or the number of times females have bred. Churcher's method (1960) of aging has several advantages in that animals can be aged up to 82+ months and that it can be applied to both sexes. Petrides method is restricted to separating young from.adults only and applies to only the male segment of the population. In the present study, age was determined by using the variations in the sutures of the skull. All specimens were collected in the winter period, January through April, so all of the animals were at least approaching the one-year-old age class. The skull sutures used as age criteria were the presphenoid-basisphenoid and the lateral palatal portion of the premaxillar-maxillary suture lying between the anterior palatine foramen and the lingual margin of the alveolus of the upper canine. The presphenoid-basisphenoid suture closes at approximately 10 to 22 months of age (Churcher 1960). The premaxillar-maxillary suture begins to close at 58 months and is completely fused at 82+ months (Churcher 1960). The shape of the postorbital processes was used to designate the 22-33 and the 34-57 month age classes and was used as an additional factor useful for checking diagnoses based on the evidence of the cranial sutures. The basioccipital-basisphenoid suture was fused on all specimens. This suture which fuses at approximately 9 months of age (Churcher 1960) thus was of little value in aging specimens collected in the winter months. The males were also aged by using the baculum as an aging criterion. 19 All males classed as juveniles fell within the 10 to 22 month age class with one exception. In that particular specimen the age as determined by the cranial sutures was used. Aging by use of the baculum is more subject to error, being dependent on the ager's opinion as to the degree of roughness and the extent of muscular attachments. As there is a complete overlapping of lengths and weights of juveniles and adult bacula, aging by the baculum had to be based on other characteristics of that bone. The basal area of the bacula is used the most. Bacula with enlarged basal areas and with roughened large muscle attachments were classed as adults, while bacula with less developed basal areas and small smooth muscle attachments were classi- fied as juveniles. When the skull of a male specimen was either destroyed or missing, the baculum was-used as the basis for aging. Skulls from 21 males and 21 females were used to determine age ratios. Both sexes were divided into 16 younger foxes (first two age classes) and 5 older foxes on the basis of cranial characteristics. It was impossible to separate the first year age class from the second year age class by using this method. The first two age classes comprised 76 per cent of the population with older foxes totalling 24 per cent. Of the five older females three were in the 34-57 month age- class, one was in the 22-33 month age-class, and one was in the 58-81 month age-class. Of the five older males two were in the 34-57 month age-class, one was in the 58-81 month age-class, one was in the 82+ month age class, and one was aged by the bacula only as an adult. The average weight of 17 males was 10 lbs. 2 ounces. Younger males averaged 9 lbs. 15 ounces; older males, 10 lbs. 8 ounces. 20 Females, based on 20 animals averaged 9 lbs. 3 ounces. Ybunger females averaged 9 lbs. 3 ounces; adult females, 9 lbs. 4 ounces. MOVEMENT OF RED FOX In this study the daily cruising range was determined by tracking 16 foxes from where their tracks were first encountered until the animals were jumped. An attempt was made to determine the daily cruising range by back-tracking a jumped fox to the previous bed. This was found to be practically impossible due to the confusion of tracks. Only one complete day's travel was recorded during this study period. One fox was tracked from.the den, back into the den, a total of 1.54 miles. I believe that weather conditions were responsible for the short distance of this trail as it was recorded the morning after a heavy snow. The animal had moved out of a den, fed on carrion, and re- turned immediately to the den. If one assumes that on the average all tracks were encountered middway along the daily travel, doubling this average figure would represent the average daily cruising range. If a fox was jumped, the straight line distance from.the point the track was first picked up, to the place where the fox was jumped, was recorded. This distance was used as a radius of a circle to determine daily hunting area. Arnold (1955), Schofield (1959), and Erickson (1955) used this method and based it on the assumption that the observer on the average intercepts a fox or bobcat trail at the mid-point, and that the average straight line distance from.the point of interception to where the animal was jumped should approximate the radius of a circle equal in size to the area over which the animal hunts in one hunting period. 21 The validity of the above assumption is unknown; however, this method does offer a method for comparing daily movements of foxes in the Upper Peninsula with the daily movements in the two areas in southern Michigan. In the present study the average straight line distance frmm the point of interception of the fox trail to the fox bed was 0.79 mile. Consequently the nightly hunting area was 1.94 square miles. This is somewhat less than in the north part of the southern peninsula (2.8 square miles) as reported by Schofield (1959) but larger than that of the southern Michigan foxes (1.4 sq. miles) as reported by Arnold (1956). Seton (1925) found foxes to have a daily cruising range of 2 to 5 miles. The average length of trail, based on 16 foxes jumped, was 1.96 miles. Doubling this figure, on the assumption that the trail was encountered at the mid point, would place the daily cruising range at 3.92 miles. The extremes of daily travel as determined from the above figures were .52 miles and 11.9 miles. This figure is probably considerably smaller than the actual cruising range due to the difficulty in distinguishing longer trails. My figures show a relatively large number of short trails. The daily cruising range is probably somewhat longer. The home range of northern foxes can only be estimated in this study. The farthest straight line distance any one fox traveled from a denning area was 2.00 miles. Due to the difficulties encountered in tracking these animals, an average home range cannot be defined. Foxes, however, in two different areas could be found consistently in 12.5 sq. miles to 19.5 sq. miles. This may indicate the home range as being 12-20 square miles. It is believed that the abundance of food determines largely the home range, and thus home ranges may vary 22 tremendously. There is some indication that foxes use regular crossings in some areas. Tracks could be found quite consistently in particular areas. When a source of food is present for a period of time, such as large carrion, definite trails lead to the source of food. In one case, foxes regularly crossed a highway to get to a dead cow. The crossing area did not exceed more than 150 feet in width, and no tracks were observed crossing in adjacent areas. In another area, I found four trails of foxes crossing a highway in an area not more than 100 yards wide. Regular trails were used as travel lanes in many diverse areas. Many trails were observed where three or more different foxes have used the trail. On these trails, old signs were observed thus in- dicating that these trails were used regularly. Well established trails seemed to be more common in open country, such as across fields and through plains areas. Approaches to the dens seem to be along established trails. Travel Reactions to Weather Foxes seemed to travel the most when there is a minimum of fresh snow, over a firm layer of snow. One to two inches of snow over- lying a crust seemed to be ideal for traveling purposes. When several inches of fresh soft snow is on the ground, movement seems to be re- stricted. During periods of heavy snowfall, tracks were not found for a period of three days in an area of heavy fox population. On one occasion, after a heavy snow, a fox moved out of the den, traveled directly to a known source of food, ate, and returned directly to the 23 den. This is very unlike usual fox behavior and may be a direct effect of the weather. Extremes of temperature did not seem to affect the movement of foxes. On February 28, 1955, foxes moved about in -20° weather. Other occurrences of travel were observed in sub-zero weather. Foxes also traveled readily in thawing weather, when the tracks melted away very quickly. Reaction to Man's Activities Even though foxes are generally found around marginal farming areas, and areas broken up by civilization, they are extremely shy of 'man. In this study, foxes reacted strongly to my tracks and presence in areas of fox concentrations. During the night, foxes hunted and traveled to within one-eighth mile of farm yards. Also, dens were found within a half mile of farms. Foxes however tended to avoid the actual farm yards and man's activities around the yards. Foxes seemed to have a deep fear of snowshoe tracks. On many occasions, foxes encountered my snowshoe trail of previous days. In all cases, the animal apparently displayed a complete distrust and fear of the track, and whenever possible avoided crossing the trail. If it was absolutely necessary to cross the trail, the animal usually jumped over the trail on the run, and continued running for considerable dis- tance. On one occasion, my trail accidently formed almost a complete square while I was tracking a fox. TWO days later in the same area, a fox was followed into the narrow opening on one side of the square. The animal soon encountered one of the trails, and after looking at it, 24 turned aside. But, since it was blocked in, almost any direction the fox went it encountered a snowshoe trail. The animal apparently got panicky after the fifth occurrence and started to run. When it came to the snowshoe trail the sixth time, it made a big leap and landed on the other side of the trail and continued running. In no case were foxes observed traveling along a snowshoe trail. This behavior is similar to that of the coyote, but wolves and bobcats, seem to accept and travel on snowshoe trails. Foxes are very sensitive to the intrusion of man in the vicinity of the dens. If snowshoe trails went too close to the den, the animals in that vicinity would refuse to use the dens for many days, and some- times weeks. On one occasion, an attempt was made to drive foxes with dogs. In the course of the hunt, two dens that had been active for the entire winter were visited. The dog and one of the hunters investigated the dens closely, leaving tracks and scent. A close check of the den area was kept, and it was observed that the foxes moved out of the dens. There was no activity at these dens for more than two weeks, although foxes moved in the vicinity of the dens. A porcupine was shot in the vicinity of an active den, to see if the foxes would utilize it as food. The porcupine was shot February 8, 1955, and allowed to lay where it fell. By the next day the carcass had frozen solid. Periodic checks were made of the carcass to see if the foxes would utilize it as food. After three weeks during which there was no utilization, the porcupine was thrown to within ten feet of the den opening. There it remained for another two weeks. A period of warmer temperatures prevailed at this time, and on March 15, 1955, the porcupine was consumed. It appears that it took a long time for 25 the human scent to disappear and for the foxes to get over their mis- trust. Dens,_Beds, and Resting Places Seton (1925) believes that, as a rule dens are seldom used in winter. However, he also reports that others have noted foxes using dens in the winter. In this study active dens were found in January, and on through the end of March. Tracks indicated that these dens were used quite frequently. On one occasion I found a den with the fox in it. Of 15 dens I found, only four or possibly five were used regularly. Of these five, three were used frequently. The dens were found in a variety of situations: four just inside the woods, three under stumps, two in small brush and shrubbery, four dug in the sides of hills, one under a brush pile, and one under a windfall. Two of these dens had three openings, one den had two openings, and allthe others had only one opening. The openings were kept clear, with very little signs of addi- tional work being done on the three most permanent dens. Ten of the fifteen dens are believed to be temporary dens, or dens being investi- gated for future use. These were all deep enough and large enough to conceal a fox. Some of these may have been more permanent, but a close observation.was not kept of these dens. From.approximately the middle of February, several places were found where a fox would dig down through the snow to the earth, dig a shallow hole and then abandon it. The openings into the dens averaged approximately 12-15 inches high and 10 inches wide, they had deep entrances through the snow (Fig. 3). In some dens the entrance path was deeply indented (Fig. 4). Other dens 26 Fig. 3.--Foxes made deep openings in snow to keep dens open. 27 Fig. 4.--Deeply indented entrance path to den indicating constant winter use. 28 were only visited at intervals and these were not dug out each time that they were visited. Foxes do not seem to lie down or sit down to rest very often in the course of a night's hunt. Beds that were found seemed for the most part to be used throughout the day. Sheltered spots, and elevated points of vantage were almost invariably used for beds. There seemed to be no specific effort to make a bed in areas frequented by prey animals. Prey animal tracks were noted near beds but it is believed that this is a matter of chance. On a few occasions beds were found in fairly open hardwoods with practically no cover. These spots were probably temporary resting beds of short duration. The beds used during the day, the semi-permanent beds, were all located at some vantage point, probably to insure comparative safety. Several beds were found in the vicinity of dens, or immediately above a den. In all cases, when the fox was jumped, it ran off, away from the den. In no case did any of these foxes go into the den. Ridges, overlooking considerable area, were popular spots for beds. Other beds were found in very thick brush, such as speckled alder (Alnus incana). In these instances the beds were on elevated logs, or mounds of snow. The beds are small and round, formed as the fox curls up and pulls its feet in under the body. Most of the beds were melted down into the snow a few inches (Fig. 5). In many beds were bits of fox fur, frozen to the bed and pulled out. In no case were remnants of food eaten by the foxes found near beds. It was noted on several occasions that a fox moved its bed as many as three times to remain in sunlight. Also, in adverse weather, foxes tended to bed down on the lee side of knolls. Three foxes were ‘l'l’llflllEE-‘E‘ll‘r‘(ri 29 Fig. 5.-'Fox bed located on knoll. (Ill {.5 II‘II’E. Jlll I! l . 30 jumped under these circumstances. On all three occasions, it was snowing heavily, thus muffling almost all of my sound. Tracks were almost obliterated and filling in with snow. Each time the fresh bed was found with fresh tracks leading away from.the bed. None of these animals were observed on the beds or leaving them. Thus it seems that the foxes depend on olfactory senses at such times, as the fresh snow made my movement almost noiseless. Foxes tend to bed down near each other when traveling together. On only one occasion did I observe more than two animals bedded down together. On that occasion five beds were found located close together. However, two animals bedding down close together was not unusual. Due to early family break-up, groups of more than two foxes together are very unusual during the winter. Movement in Relation to Vegetation Types Foxes tend to meander in their travels and investigate several cover types in the course of their daily (or nightly) travel. During the period of January through March, 1955, I followed 54 fox trails for a total of 173,163 yards or 98.4 miles. The foxes changed cover types 359 times during that distance, or an average of a new cover type every 482 yards. They exibited a tendency to use cover type edges, meandering in and out of adjacent cover types. Foxes seldom traveled for more than 1,000 yards in any one cover type. (Fig. 6). As the study area was well interspersed with several cover types, the vegetational cover types were grouped into nine main categories (Table l). Foxes tended to pass from one cover type to another in a random manner. 31 Number of occurrences up med oouoaco no: on»» coaowpouob panacea cuckoo ooaaaup one: noxou mouse a“ cocaoean seawammammammmmmmmmm metamaaaamaaaamaammt 3%im3mmmn2mmm.niss )ihiflishi # .moohu cowumuowo> canoes mowoowoumo moomumfio ow mHHmou xom mo monsoonooo mo hoaonvoow om>uomoo onHun.o .wwm 0H ON on 0: (queo 19d) seoueaanooo JO Tousnbaag 32 TABLE l.--Winter habitat use by red foxes during 98.4 miles of tracking in central Upper Peninsula of Michigan - 1955 Linear Distance Per Cent Vegetational Types in Yards of Use Upland hardwoods 75,964 43.9 Open areas 35,947 20.7 Mixed hardwood conifers 17,426 10.1 Semi-open 7 16,788 9.7 Marsh, lowland brush, streams. 9,470 5.5 Coniferous swamps 15,431 8.9 Pine plantations 999 0.6 Upland brush 761 0.4 Roads 377 0.2 Total 173,163 100.0 Four sections (2,560 acres) in Alger County were chosen as typical of the study area. Foxes were trailed through this area on several occasions. The diversity of habitat and percentage of individual vegetational types are representative of this study area. A cover map was made of this area to determine the approximate amount of each cover type available for use by foxes (Fig. 7). In this study the foxes trailed hunted fairly uniformly through the available cover types (Table 2). There seemed to be some preference for coniferous swamps, semi-open areas, and the mixed hardwood-conifer timber types. The upland hardwood type, although the most prominent cover present, was not used in proportion to its availability. Move- ment in relation to cover types are discussed as follows: 33 Sections 2, 3, 10, 11 Town 45 N, Range 21 West N A L \\ _ . ; ’7 [/1 / /[ fl \ \ \i . \ - _ Scale 2-1/4" = 1 mile 1...... = Open in“ = Swamp Conifer .L__, = Upland Hardwood = Upland Brush '-- Semi-Open = Stream-Lowland Brush Hardwood-Conifer [5 Farm Sites Fig. 7.--Cover map of 2,560 acres considered most typical of the study area. ‘Illll f‘illlli i [I III- l I. I 34 TABLE 2.--Habitat availability as determined from 2,560 acres considered most representative of the study area, and fox use during 98.4 miles of tracking Per Cent of Per Cent Cover Type Area in Type Use Open areas 22.5 20.7 Semi-open 8.8 9.7 Upland hardwood 52.1 43.9 Mixed hardwood ‘ conifers 9.2 10.1 Coniferous swamp 5.3 8.9 Marsh, lowland brush streams 0.5 5.5 Upland brush 0.6 0.4 Roads 0.1 0.2 Open The open areas consisted of pastures, hay fields, and abandoned idle fields. These fields are generally interspersed throughout the other vegetational types and are generally not more than 40 to 60 acres in size. Foxes used such areas 21 per cent of the tracking distance in this study. Foxes used this type habitat 98 times during the winter with the average trail being 367 yards long. As in the other vegeta- tional types, the foxes tended to meander across the fields in an attempt to find food. Foxes tended to stay fairly close to the edges of the openings while searching for food. Seldom were small openings passed up in the course of the travel. One attempt to capture prey each 1,239 yards was the average, with one kill per 7,189 yards recorded (Table 3). 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