Chapter 2

PLATE 46

PLATE 47

PLATE 48

When moving undisturbed through the woods cottontails usually do not pause to forage or associate with other cottontails, but keep to a straight route except in severe weather, when, as noted above, they find resting places in the woods. Ninety-two per cent of the cottontails captured in live-traps were captured within 100 feet of a woodland edge; six per cent were captured in the woods, more than 100 feet from an edge, and two per cent were captured in grassland more than 100 feet from the edge. In winter, when the air temperature was less than 20° F., 22 per cent of the cottontails were captured in the woods more than 100 feet from the edge.

The maximum distance between two centers of activity of an individual was 700 feet, average 550 feet. If two centers of activity were maintained, the cottontail usually traversed the entire home range every seven to 11 days.

In no case was a cottontail known to have lived in two woodland edges which were separated by open grassland. Cottontails usually did not move more than 75 feet from suitable cover. In winter when herbaceous vegetation was dormant cottontails did not cross open fields.

Forms in grass clumps were the usual resting place for cottontails, but others in brush piles, rock outcrops, and tree stumps were also used. On the average a cottontail maintained 3.5 forms. If disturbed repeatedly at a form, a cottontail would permanently desert it. On seven occasions a cottontail used a form that had been used by another within 24 hours. Three cottontails used the same shelter under a rock ledge in five days; one was under the ledge on December 17, 1955, and another was there on December 18. The first was there again on December 20 and a third was there on December 21. The original cottontail had returned by January 2, 1956. There may be 20 to 30 resting places used by cottontails within a single home range area since five to seven cottontails may live there as co-occupants at one time. Two cottontails, both males, lived together in a _Smilax_ thicket for three weeks, resting within 15 inches of each other. Occasionally a female was present in the same thicket, and rested about three feet from the males.

A male trapped on land adjoining the Reservation and confined overnight at the Reservation headquarters escaped the next day and was seen 32 days later, 1800 feet from the point of escape, back in the area where it was originally captured.

A female confined for observation, escaped and ran in the direction opposite from her home. Subsequently she was seen on four different occasions, over a period of one month, in her original home range, 1,100 feet from the point where she escaped. Both these animals which made homing movements had been removed in cloth bags from their homes.

Another cottontail removed from its home range and taken to the laboratory building to be marked, escaped and ran to a nearby wooded hillside without pursuit where it could be observed because of snow on the ground and lack of leaves on the trees. The animal ran and hopped about over a one-half acre area. Its movements seemed to be unoriented and it frequently stopped and stood on its hind legs in order to look about. After 10 minutes of this behavior, a red-tailed hawk (_Buteo jamaicensis_) screamed as it flew overhead. The cottontail, stimulated by seeing and/or hearing the hawk, ran faster, moving in circles until it disappeared from view five minutes later. When last observed the cottontail was 1,700 feet from its home range and was headed in the opposite direction. It had passed several potential shelters but had not attempted to use them, presumably because it was not familiar with the area. Although for several months afterward traps were operated in the cottontail's home range area and in the area where it escaped, the animal was never recaptured.

SIZE AND SHAPE OF HOME RANGE

Of the 89 cottontails observed in the study, 35 were captured in live-traps only once and were never seen in the field or trailed. The remaining 54 served for calculation of home range by one or more methods. The minimum, maximum and average home ranges for these 54 individuals were calculated by each of five methods. All individuals for which any area was recorded were included in the average. Incomplete home ranges lower the averages. According to the most reliable method (Composite Method) 30 male cottontails had home ranges of between 0.46 acre and 12.19 acres and 24 female cottontails had home ranges of between 0.46 acre and 12.62 acres. The average for males was 5.05 acres and the average for females was 4.81 acres. The average for all 54 cottontails was 4.86 acres.

Because of irregularities in live-trapping and field observation some cottontails were more intensively studied than were others; one cottontail was followed one time only, while another was trapped 26 times, followed three times, and seen in the field six times. It was necessary to determine which cottontails had been studied sufficiently to determine the approximate extent of their home ranges.

The average area, in acres, of home range was plotted, on a graph, against the number of peripheral points (Figure 1). When a home range had nine or more peripheral points, on an average, the size of home range did not increase significantly with additional captures, observations in the field, or records of trails. Home ranges with less than nine peripheral points were likely to be increased in size with each new observation. A similar situation has been shown by previous authors who have plotted the size of home range against number of captures in live-traps, where only live-trapping was used to gather data. Therefore, in my study, home ranges with nine or more peripheral points were considered to be adequately studied.

Data for eighteen cottontails that had been studied sufficiently to determine the full extent of their home ranges were used to calculate minimum, maximum, and average home range by each of five methods (Table 1). The methods used by Schwartz (1941), Dalke and Sime (1938) and Allen (1939) yielded results which were lower than any others, presumably because only live-trap data were used and because straight lines were used to connect traps in which cottontails were captured. The "composite method" was considered the most reliable because it utilized all data gathered for each individual and because with this method the home range boundaries were drawn to enclose all areas in which the cottontail lived and excluded all areas in which the cottontail was not known to have been. The method used by Fitch (1949) agreed most closely with the "composite method" and suggests to me that the home range of animals can be estimated with reasonable accuracy by this method when field observation or trailing are not feasible. The composite method is superior to others for studying the home range and movements of cottontails.

Of the individuals whose entire home ranges had been thoroughly studied, nine males had home ranges of between 4.72 acres and 12.19 acres with an average of 8.92 acres; nine females had home ranges of between 2.42 acres and 12.62 acres with an average of 7.76 acres. The average size of home range for both sexes was 8.34 acres (Table 1).

TABLE 1.--HOME RANGES, IN ACRES, OF 18 COTTONTAILS ON THE RESERVATION IN 1956, COMPUTED BY FIVE DIFFERENT METHODS.

======================================================================= | | Number of | Average | Maximum | Minimum Method | Sex | individuals| area | area | area ----------------------+-----+------------+---------+---------+--------- Allen (1939), | (M) | 9 | 2.00 | 6.78 | .30 Dalke and Sime (1938) | (F) | 9 | 2.54 | 7.20 | .35 and Schwartz (1941) | all | 18 | 2.27 | 7.20 | .30 +-----+------------+---------+---------+--------- | (M) | 9 | 4.01 | 12.89 | 1.05 Fitch (1947) | (F) | 9 | 5.68 | 11.50 | 1.84 | all | 18 | 4.85 | 12.89 | 1.05 +-----+------------+---------+---------+--------- | (M) | 9 | 7.20 | -- | -- Fitch (1949) | (F) | 9 | 9.00 | -- | -- | all | 18 | 8.40 | -- | -- +-----+------------+---------+---------+--------- Tracking and | (M) | 9 | 8.74 | 11.15 | 3.54 field observations | (F) | 9 | 8.62 | 12.18 | 5.51 | all | 18 | 8.69 | 12.18 | 3.54 +-----+------------+---------+---------+--------- Tracking and field | (M) | 9 | 8.92 | 12.19 | 4.72 observations plus | (F) | 9 | 7.76 | 12.62 | 2.42 live-trapping | all | 18 | 8.34 | 12.62 | 2.42 ----------------------+-----+------------+---------+---------+---------

Cottontails range over a larger area in summer than they do in winter because suitable cover and food is more abundant in summer. One cottontail (Figure 2, upper left) lived in a woodland home range of 4.6 acres in the winter but increased the range to 6.5 acres in summer by crossing the narrow overgrown end of a field to another woodland area. Another cottontail (Figure 3, top part) lived in a woodland home range of 7.9 acres in winter but in summer increased the home range to 9.5 acres by including also a part of an adjacent field. Other cottontails increased their home ranges in summer by five to 15 per cent.

On the average, male cottontails had a larger (by 13 per cent) home range than females probably because of the increased activity of males in the breeding season and the decreased activity of females when pregnant and caring for young. Nevertheless, some of the largest home ranges measured were those of females.

The size of the home range in immature cottontails varies between 0.1 acre and 4.0 acres, depending on the age and size of the individual. Fourteen young cottontails between three and six weeks of age did not leave areas of approximately one acre in each instance. Nine cottontails between six weeks and 18 weeks of age lived in areas of about two acres. By the time cottontails are four to five months old they inhabit a home range of four to eight acres.

One cottontail (Figure 2, lower left) born in July, 1954, was estimated to have wandered over approximately 0.25 acre at an age of three weeks. In September this cottontail occupied a home range of one and one-half acres. By December it was five months old and occupied an area of about eight acres. In the next year it enlarged its home range to 11.5 acres.

The cottontail usually settles down in one area and stays there until it dies. Changes from one home range to another are unusual, but minor shifts, in response to changes in vegetation and weather, are common. In one exceptional instance (Figure 2, right) a male cottontail, occupying a home range of 11.2 acres in a woodland, suddenly shifted to a new area that barely overlapped its former home range at one edge. Two months after the change was first noticed the cottontail was living in a new home range of 6.6 acres 300 feet from its original home range. In changing from one home range to the other the cottontail traveled along a dry stream bed and was captured there three times.

Maps of the home ranges of four of those 18 cottontails for which sufficient data were collected to determine the size of home range are shown in the lower part of Figure 3.

SUMMARY AND CONCLUSIONS

The home range and movements of the cottontail were studied on a 90-acre area of the University of Kansas Natural History Reservation from February, 1954, to March, 1956. Eighty-nine cottontails were identified in the field 59 times, trailed 70 times and captured in live-traps 326 times in 7,850 trap nights. Home range of the cottontail was calculated by five methods, using the same set of data, and the results were compared. A composite method was used, which permitted the use of more data than any other one method.

The maintenance of a home range is of survival value to the cottontail. Knowledge of the home range is of value to man when control or propagation of cottontail populations is desired. Cottontails establish a home range where they are born and enlarge it to nearly full size the first winter. Home ranges of cottontails are overlapped by those of others regardless of sex or age. No territory is maintained.

The cottontail makes movements to forage, to seek cover from predators and the weather, to reproduce, build nests, care for young, keep pace with changes in vegetation through the year, and escape unusually severe climatic conditions. Movements may be caused by desire for acquaintance with surroundings and other animals, escape from undesirable surroundings or animals, or merely release of nervous energy.

When foraging, cottontails moved 175 to 325 feet per day, mostly near woodland edges, and used from 10 to 20 per cent of the home range. When escaping from predators cottontails moved 30 to 1200 feet and used 5 to 70 per cent of their home ranges, depending on the type of pursuit. Some cottontails that were followed, ran in almost circular courses for as far as 3000 feet and covered as much as 90 per cent of their home ranges. Paths or runways were not used except in deep snow or very dense vegetation. Movements were limited by deep snow. When temperatures were unfavorably high or low, cottontails sought cover deep in the woods or under rock outcrops, and in dry stream beds. In moderate weather resting places in grass forms, brush piles and thickets were used.

Both males and females moved farther in the breeding season than in the rest of the year, but females that were caring for young in summer and late spring moved shorter distances than they did when not so engaged in autumn and winter.

Cottontails were most active at dawn and especially, dusk, and were more active on dark nights than on moonlight nights. Cottontails were most active when the air temperature was between 0° F. and 33° F. and when rain was not falling. Activity increased as the percentage of ground covered by snow increased and as the abundance of food decreased. Activity did not vary with physiological condition except that as body weight decreased activity increased--probably because of lack of food.

The home range is used most intensively near centers of activity that are near woodland edges or in other areas of good cover. Cottontails often ranged through the woods and along edges but did not cross open areas more than 75 feet wide. Cottontails use their home range most intensively in winter when they are forced to move long distances in poor cover, searching for food. More than one cottontail may use sites of good cover at the same time and two or three used the same resting place at different times.

Two instances of homing were observed; cottontails moved 1,100 and 1,800 feet to return to their home ranges, but one cottontail that escaped 1700 feet from home failed to return.

The average home range of 18 cottontails for whom adequate data were gathered was 8.34 acres. The home ranges of males averaged 1.16 acre larger than those of females. In summer, cottontails increased their home ranges 5 to 15 per cent by taking advantage of cover provided by the more abundant vegetation. Cottontails three weeks to five months of age lived in home ranges of between 0.1 and 4.0 acres and enlarged their home ranges almost to their ultimate full size in the first winter.

LITERATURE CITED

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