Home Range And Movements Of The Eastern Cottontail In Kansas Part 1

Home Range and Movements of the Eastern Cottontail in Kansas.

by Donald W. Janes.

INTRODUCTION

A knowledge of the home range and movements of the cottontail (_Sylvilagus florida.n.u.s_) is one of the most important prerequisites for estimating effectively its numbers and managing its populations. By comparing results obtained from different methods, previously used, for determining the size of the home range I have attempted to develop a more valid procedure.

The study here reported upon was made on the University of Kansas Natural History Reservation (Sec. 4, T. 12S, R. 20E), the northeasternmost section of Douglas County, Kansas, approximately 6-1/2 miles north-northeast of the University campus at Lawrence. The 590-acre reservation, situated in the ecotone between the eastern deciduous forests and the prairie of the Great Plains near the north edge of the Kansas River Valley, has been protected as a "natural area"

since 1948 (Fitch, 1952). It consists of tree-covered slopes, and flat gra.s.s-covered hilltops and valleys. Two limestone outcrops follow the contours about five and 20 feet below the tops of the hills.

The 90-acre study area consists of a valley bordered on the north by a wooded slope and on the southeast by another wooded slope adjacent to a narrow hilltop, east of which is another wooded slope. The area is thus an alternating series of three wooded slopes and two gra.s.s-covered, relatively level areas.

The wooded slopes rise from the valley for about 125 feet at a grade of approximately 16 per cent. There is a sharp increase in grade to 36 per cent 100 feet below the top of the hills. A natural terrace 50 feet to 100 feet wide parallels the hilltop at the base of the 36 per cent incline.

The vegetation of the northwest-facing wooded slopes has been described by Packard (1956). It consists of American elm (_Ulmus americana_), s.h.a.gbark hickory (_Carya ovata_), chestnut oak (_Quercus muehlenbergii_), black oak (_Quercus velutina_), and black walnut (_Juglans nigra_), in that order of dominance. Honey locust (_Gleditsia triacanthos_) and hackberry (_Celtis occidentalis_) are also present.

Shrubs and herbs of the lower story include greenbriar (_Smilax hispida_), wild grape (_Vitis vulpina_), Virginia creeper (_Parthenocissus quinquefolia_), coralberry (_Symphoricarpos...o...b..culatus_), gooseberry (_Ribes missouriense_), bluegra.s.s (_Poa pratensis_), sedges (_Carex_ sp.), poison ivy (_Rhus radicans_), and white snakeroot (_Eupatorium rugosum_).

The flat hilltops are covered by a mixture of gra.s.ses and forbs but are dominated by awnless brome (_Bromus inermis_). Foxtail (_Setaria glauca_), false redtop (_Triodia flava_), and panic gra.s.s (_Panic.u.m clandestinum_) also occur commonly. Awnless brome is dominant in the valley (Pl. 46, fig. 1; Pl 47, fig. 2) except in the eastern end where bluegra.s.s is dominant (Pl. 45).

Near the tops and bottoms of the slopes barbed wire fences separate the woodlands from the gra.s.slands, which were grazed until 1948. The borderline between woods and gra.s.slands is well defined but woody plants are rapidly encroaching into the gra.s.slands. Young Osage orange (_Maclura pomifera_), American elm, and hackberry are common trees encroaching on the gra.s.slands. The edge vegetation between woods and fields (Pls. 45 and 47) includes smooth sumac (_Rhus glabra_), coralberry and wild plum (_Prunus americana_). The lowland edges are characterized by blackberry (_Rubus argutus_), greenbriar and elderberry (_Sambucus canadensis_). Plates 45, 46 and 47 all show local habitat in situations where traps were actually operated. Fitch (1952:8-22), Leonard and Goble (1952:1015-1026) and Martin (1956:366-372) have described parts of the Reservation that include the study area.

I am grateful to Professor Henry S. Fitch for guiding my work, to Professor Rollin H. Baker for suggestions and encouragement in the early part of the study, to Mr. Robert L. Packard for certain trapping records that supplemented my own, and to Professor E. Raymond Hall for valuable suggestions. Norma L. Janes, my wife, typed the ma.n.u.script.

Photographs were taken by me. The State Biological Survey of Kansas provided funds, equipment, and transportation.

METHODS AND TECHNIQUES

Schwartz (1941), Dalke and Sime (1938), Dalke (1937 and 1942), Hendrickson (1936), and Allen (1939) estimated the home range of the cottontail by drawing, on a map, straight lines that connected all marginal points of capture in live-traps. The resulting home ranges were polygonal figures. Haugen (1942) altered this method by drawing lines that connected points midway between the actual points of capture and the next outermost traps in the grid. Fitch (1947) used a method for enclosing all points of capture in a circle or ellipse that represented the home range boundaries and expressed home range as the diameter of these figures. Another method, which has been used to determine the home range of birds, is to map the movements of an individual as it is observed. Stebler (1939) suggested the use of tracking records to determine home range. Connell (1954) expressed home range of cottontails as the average distance traveled from a computed center of activity. The method was originally proposed by Hayne (1949).

The methods used by other investigators to calculate the home range of the cottontail have yielded estimates varying from 0.1 acre to 100 acres. Such wide variations in the estimated size of home range may result from the use of different methods and from insufficient data.

The data obtained from live-trapping are not fully adequate because traps cannot sample, in time and s.p.a.ce, the entire home range of an individual. Also, "trap habit" or "trap shyness" may distort the apparent shape of the home range. In order to compare these methods I have calculated home range from my data by each of five different methods. The results are shown in Table 1.

No two methods yielded exactly the same results. To utilize all available data for each individual, I recorded on a map the locations of capture in live-traps, nests and forms, locations where the animal was observed in the field and the routes that it took between them. At the end of the study a line was drawn on the map to enclose the areas where the cottontail was known to have been.

Live-traps were operated intermittently at 130 stations between December 8, 1954, and February 10, 1956. Sixteen cottontails were marked in the same area by Robert L. Packard in 1954. Data from 7850 trap nights were used in this study. The traps were set at fifty-foot intervals and the pattern approximated that of a grid in habitat favorable for cottontails such as at edges of woodland. In wooded areas traps were placed at fifty-foot intervals parallel to the edges. Traps were not set on areas of poor habitat where neither cottontails nor their sign were observed.

The traps were operated eight to twelve days and closed for two to five days intermittently throughout the trapping period except in the months of April to August, 1955, when trapping was unsuccessful because the cottontails then were not attracted by bait.

Two kinds of traps were used in my study: those made by the National Live Trap Company and those described by Fitch (1950). Both types performed well and were serviceable under ordinary field conditions.

Experiments were made periodically throughout the trapping period to determine which bait was most attractive to cottontails and least attractive to birds, rodents, skunks, racc.o.o.ns, and opossums. All of these animals hindered operations by stealing bait and springing traps.

Corn, scratch-feed, carrots, parsnips, tomatoes, lettuce, apple, cabbage, raisins, sorghum, sugar candy, and onions were used as bait.

Corn and scratch-feed attracted cottontails best in all seasons. Corn was superior to scratch-feed, which was quickly stolen by small birds and rodents. Eighty-nine cottontails (40 females, 49 males) were captured in the course of the study.

Cottontails were marked individually at the time of first capture. When necessary, the markings were renewed at later captures; in all such instances the same color codes and numbers were retained for each.

Markings were of four types: numbered ear tags, colored ear ribbons, colored tail fur, and colored feet. It was intended to make each individual cottontail recognizable in a trap or in the field.

Occasionally when a predator had killed and eaten a cottontail the tail and feet remained and, when dyed, they provided important clues to the ident.i.ty of the individual. However, the color of the feet is not ordinarily discernible in the field while the rabbit is alive.

Monel metal ear tags (size No. 4, National Band and Tag Co.) were punched through the lateral or posterior fold of the ear close to its base (Pl. 48), one in each ear as insurance against possible losses.

However, only three tags were pulled out of the ears and lost in the course of this study. In no instance was ident.i.ty of an individual cottontail lost. The tags caused no damage to the ears over a period of 21 months.

Trailing in snow is an effective method of studying the daily activities. The record preserved by the tracks becomes somewhat confused after the snow has lain on the ground for more than one night, and after the third night it is impossible to read the surface of the snow. The first day of thaw usually ends tracking because the investigator loses the trail when it crosses a patch of bare ground.

The use of a dye on the feet of the individual to be trailed eliminates much of the difficulty of determining which tracks are to be followed.

One or more feet can be dyed when the investigator handles the animal in releasing it from the trap. The trail of dyed footprints is distinguishable from all other rabbit tracks in the area. Even when only patches of snow remain, the animal can be followed by checking the edges of the snow for the emerging footprints of the marked rabbit. The same dye is used to color the tails. The color persists in the footprints for about three hours, over a distance of 600 to 800 yards.

The animal leaves only a small spot in each footprint, but when it pauses, the mark is large. Red dye makes the most conspicuous mark in the snow.

Thirty-one rabbits were trailed 68 times with one to six records for different individuals. Almost two-thirds of the trailing records pertain to males, which were caught more easily than females while snow was on the ground.

The trail, for both s.e.xes, in those individuals released and followed immediately was longer than in individuals released and allowed to move away before they were followed. The area ranged over by a trailed individual was not significantly greater in either case. The area ranged over was greater by day than by night. Individuals continued to move while being followed in the day, but stopped to forage and look about at night.

Records were obtained by identifying cottontails that I flushed from forms as I walked through the study area, sometimes using a noise-making device or dragging a rope. Regular search was made along the hilltop rock outcrops, under which hiding cottontails could be identified with the aid of a flashlight. Forms in brush piles, and thickets were visited and the inhabitants identified. Other persons, working on the study area, supplied some of the records of cottontails that were seen alive or found dead. Also through binoculars or a telescope I watched movements of undisturbed individuals. Twenty-three individuals were identified 59 times. Nine females were seen 28 times and 14 males were seen 31 times. Sixty-five other individuals were seen, but could not be identified in the field.

MOTIVATION AND EXTENT OF MOVEMENTS

The home range is an area in which an animal carries on its normal activities of eating, resting, mating, caring for young, and escaping from predators. The cottontail establishes a definite home range and may live its entire life within this area, which permits familiarity with food sources, hiding places, and escape routes.

The cottontail usually establishes its home range in the area where it was born, being semi-gregarious and tolerant of crowding. Eight cottontails that were captured and marked as young remained in the area of original capture after becoming adults. Two of them lived 17 months in the same area, two lived 14 months, two lived 13 months, one lived 12 months and one lived eight months. No young were observed to have moved to another home range after they matured, although some may have moved off the study area and thereby escaped observation.

Young become independent and are seen foraging and moving about by the time they weigh 200 to 300 grams, at an age of four to six weeks. They a.s.sociate with other young of the same litter and neighboring litters, and frequently frolic together. When two to three months old and weighing 400 to 700 grams they begin to live a more solitary life and usually rest alone in forms. Fourteen young between one and six weeks of age never were recorded to have moved more than 150 feet.

The population reaches its peak in August or September; home ranges varying in size from one-half acre (in young ranging in size from 150 grams to 800 grams) to 12 acres, in adults, are superimposed upon each other. In a woodland area of approximately 21 acres 33 cottontails were living together in September, 1955.

As the growing season ends and winter approaches, the amount of food available to the cottontail decreases and the cover becomes spa.r.s.er (Pls. 45 and 46); predators, disease, and weather take their toll of the young. The survivors must move farther to find adequate food and cover. The home range of the cottontail in the first winter is overlapped by the home ranges of the other members of the same litter, and members of other litters, as the home range is enlarged to approximately its full size. By April the population reached its annual low point; nine of the original 33 cottontails were known to have survived on the 21-acre area of northwest-facing wooded slope south of the pond.

Foremost among the needs of the cottontail are food and cover. Daily movements motivated by these needs are the most frequent and most extensive that it makes. Movements such as are a.s.sociated with courting and mating, escaping severe weather, escaping from predators, and caring for young are seasonal or irregular in occurrence.

Because the abundant vegetation of summer provides adequate food and cover, movements made while foraging and seeking concealment are less extensive than those made in winter when leafy vegetation is absent and food is scarce. The average length of trails of foraging cottontails was 175 feet per day in summer (11 individuals observed without disturbance) and 325 feet per day in winter (22 individuals trailed or observed without disturbance).

In the spring and summer cottontails forage mostly near woodland edges for gra.s.s and herbs, and usually wander no more than 40 feet into the gra.s.slands from the protection of woodland edges and thickets. In autumn and winter cottontails forage in woods and along woodland edges for bark of trees and shrubs and for fallen fruits of trees. Ninety-two per cent of all fecal pellets found in gra.s.sland were within 40 feet of cover suitable for cottontails.

Movements made by the cottontail while foraging appear aimless; typical behavior consists of progression with a hesitant gait of two or three hops, a stop to eat, another series of hops and another stop.

Footprints made by this movement are about 12 inches apart. With occasional spurts of hopping the individual moves perhaps ten to twelve feet where it stops and begins to eat again. The area in which the individual forages is usually elongated with its long axis parallel to the edge except in areas of uniform habitat (such as large patches of coralberry) where the area covered tends to be more nearly circular.

Cottontails observed foraging were estimated to utilize 10 to 20 per cent of the home range area in one evening. Paths or runways are not ordinarily utilized by foraging cottontails.

In seeking protection from predators or from the weather, cottontails move farther in winter than in summer. The average length of trails of cottontails flushed by me in the study area was 80 feet in summer and 210 feet in winter.

When cottontails were released from live-traps they ran an average of 30 feet before stopping to look about. Cottontails always ran toward the densest cover within 50 feet of the point of release. Ten per cent of the cottontails released from live-traps did not stop running until out of sight (always more than 30 feet).

Movements made by cottontails escaping from predators differ from movements made while foraging. The gait is a full run, often eight to ten feet between footprints in snow; the trail is either straight or slightly zig-zag. If possible, the individual will take refuge in a hiding place such as a rock outcrop, brush pile, or thicket. Eight cottontails emerged from such hiding places an average of 22 minutes after the disturbance ceased.

If unable to find a hiding place a pursued cottontail will run 600 to 1200 feet while circling and returning to the area from which it ran.

If not closely pursued, it will usually (in 68 per cent of the instances) not enter hiding places, but continue to run ahead of the pursuer. Of 70 released from live-traps and followed, 23 sought refuge in hiding places. The others ran slowly (4 to 7 feet between footprints in the snow) with frequent pauses to look and listen; they usually succeeded in keeping out of my sight. Twelve times the trails of cottontails followed in this manner pa.s.sed near a form, or other resting place; always the cottontails had paused at the resting place, and twice the individual went into the resting place and ran out again when I approached. Resulting trails were almost circular, covering most (70-90 per cent) of the home range; sometimes three or four complete circuits were made. The trails made when I pursued cottontails ranged in length from 800 to 3,000 feet. A trail recorded for an individual on one night was almost identical with another trail for the same individual recorded another night. The cottontail is not easily driven out of its home range. Paths or runways are used by cottontails escaping from predators in dense vegetation along fence lines, in thickets, or brush piles, or in snow that is eight or more inches deep.

Most of the year cottontails rest in forms of gra.s.s or brush near woodland edges but in extremely cold or hot weather they seek the greater protection of the woods. Movements are limited to the woodlands in severe weather, especially when deep snow makes travel difficult.

Hilltop rock outcrops on the area provide excellent protection for the cottontail especially from low temperatures and freezing rain or blowing snow. Eighty per cent of the cottontails resting under the rock outcrops were found in severe winter weather. Fifteen per cent were found in severe summer weather, and five per cent were found at times when the weather was not severe. Undercut creek banks and exposed tree root-systems in eroded gullies were favorite hiding places. Brush that had acc.u.mulated in the ravines and stream beds also was used for cover by the cottontail.

In heavy rain a cottontail may move along, neither hopping nor running, with its body close to the ground, head low, ears laid back. Losing its customary alertness it may pa.s.s a person without seeing him. At times, I have been able to approach almost close enough to seize one of the miserable creatures. In deep snow cottontails may progress with long bounds carrying them high enough vertically, to clear the surrounding snow.