Part 4

(7.) This male was first caught in June, 1949, as a juvenile probably between two and three months old (weighing 96 grams) and hence probably still at the maternal house. In September, grown to adult size, he was caught twice, still at this same place. In October, November, December, and in February, 1950, he was caught 11 times at eight places all within a 90-foot radius of his original location. In April, 1950, he was caught at points 550 feet WSW and 700 feet SW. In October he was caught within 150 feet of the original location. In November, 1950, and in March and April, 1951, he was caught four times at a place 900 feet SW from his original location.

(8.) This subadult male was first caught at the hilltop outcrop on October 4, 1949. Two days later he had moved 160 feet north along the outcrop. A month later he had shifted 600 feet south; in three more days 1040 feet north. On November 15 he was 105 feet south of the November 8 location; on November 16, he had moved 70 feet north. On November 17 he had moved 900 feet back south, but had returned on the 18th to the November 16 location. On November 22, he had again shifted 900 feet south. All capture sites were at the hilltop outcrop.

(9.) This male was caught as a juvenile (75 grams) on October 8, 1950. On November 9 he had moved 220 feet, from the lower outcrop to the upper, and he was recaptured at or near this same site on November 10, 28 and 29, and on January 11 and February 9, 1951. On November 21, 1951, grown to maximum adult size, he was caught at a new location 1080 feet from the original.

(10.) This male was caught as a subadult twice at the same place on November 30 and December 14. By the following autumn he had shifted to a new location 180 feet south along the outcrop, and he was caught there on September 22 and October 18, 1951, and on January 20 and February 2, 1952.

Females

(11.) This female was captured 27 times over a span of 211 days. She moved back and forth considerably between two houses 40 feet apart but made only one substantial movement of 245 feet; at this time she was in breeding condition. Nearly seven months after the first capture she was seen for the last time only 16 feet from the original site of capture. It was assumed she fell prey to spotted skunks which were raiding traps.

(12.) First captured on March 24, 1951, she remained on the area 105 days in which period she was live-trapped 25 times. Sixty per cent of the total captures were at the same house and the longest movement recorded was only 56 feet. She was last caught in a trap 25 feet from the site of original capture.

(13.) This young adult remained at her house at the rock fence approximately four months. In this period she was captured 11 times. On March 16, 1952, she had moved 410 feet to a house at the eastern section of outcrop, probably searching for a male. She was never seen again.

(14.) This subadult female moved from the site of original capture to a house 253 feet away on the same outcrop. She was probably in search of a new home when caught the first time. She was recorded at another house 40 feet away on one occasion.

(15.) Over a span of 90 days and 15 captures this female was not recorded as making any movement. She was living in one of the woodland houses. Mature males were numerous in the area and she was visited by at least two.

(16.) This female was also living in the woodland section and was first caught on March 30, 1952, in one of the less favorable houses. She was trapped 17 times over a period of 85 days. One movement of 68 feet to a new home site was recorded, but the area of foraging probably did not change. She was caught here four times and then disappeared.

(17.) This female was first trapped as a subadult on October 5, 1948, at a house in brush on the upper part of a north slope. On November 24 she had shifted 590 feet to the bottom of the slope and was living in the recess beneath an undermined honey locust on a gully bank. On November 25 she was caught in a similar situation 100 feet farther east along the gully bank. She was recaptured at the gully on November 26 and 30, December 1, 3, 22, and March 8 and 9, and in all she shifted six times between the two gully-bank dens.

(18.) This female was first trapped as an adult on November 18, 1948, in a gully-bank den. She was recaptured at this same place a year later, on November 18 and 30, 1949. On February 19, 1950, she was caught at a hollow sycamore 650 feet farther up the gully, and she was recaptured there on February 25 and April 7, and on June 15, 1951. On August 6, 1951, she was caught at a house in a thicket on the gully bank, between the first and second locations and 150 feet from the latter.

(19.) This female was recorded only twice; on October 15, 1948, she was at a hilltop rock outcrop. On July 14, 1950, she had moved 1480 feet and was living in a rock pile at the base of the slope, near the same hollow sycamore where female No. 18 had been caught.

(20.) This female was first caught as an adult on April 5, 1950, at a large boulder of a hillside rock outcrop. On October 7, 1950, she had shifted 110 feet to a house at an osage orange tree on the hilltop rock outcrop. On November 9 she was back at the first location and on November 28 she had moved 70 feet south along the hillside outcrop. On January 11 and February 9, 1951, she was back at the original location. On November 9, and 21, 1951, she was again at the site 70 feet south, and was still there at her last capture on February 3, 1952.

Ordinarily each house that is in use harbors only a single woodrat. To a greater degree than any other kind of mammal on this area woodrats show intraspecific intolerance. On various occasions when captives were placed in the same or adjacent cages, they focused their attention on each other with evident hostility, the more powerful or aggressive individuals attacking or pursuing. Several times the confinement of two rats in the same live-trap or cage resulted in the death of the weaker individual, and seemingly this is the normal outcome unless the attacked rat is able to escape. On various other occasions two or more rats have been caught in the same trap simultaneously but in every instance these were either: a pair of adults, the female appearing to be in oestrus; a lactating female and one or more of her young; or young less than half-grown, that were obviously litter mates. Older woodrats, especially males, often have their ears torn and punctured from fighting.

Territoriality involves, primarily, defense of the house itself. An individual that ventures into an occupied house may be quickly routed by the occupant even though the latter is smaller. Chasing has been observed occasionally, but it is doubtful whether any individual is able consistently to defend the entire area over which it forages. Because each rat spends most of its time within the shelter of its house, an intruder might venture onto its home range unchallenged and undetected, so long as it did not enter the nest cavity.

An adult female was live-trapped on October 14, 1951, beside her house at the outcrop. As soon as she was released, she disappeared within the house. After approximately two minutes, a soft, high pitched whine was heard and immediately another woodrat dashed into view closely followed by the female. The chase continued for several seconds in the vicinity of the house, but the woodrat being chased soon left the area via the outcrop. Probably this intruder had moved into the house in the night while the female was in the trap.

On June 17, 1952, an adult male was found in a live-trap set at one of the brush pile houses in the woodland area. This house was occupied by an adult female. He ran into the house after release, and immediately there was a loud squeal. He ran outside and paused under some limbs approximately 15 feet from the house, and remained there for 15 minutes before clipping off an ironweed 12 inches long, which he carried to the house. He did not enter the house but stopped beneath overhanging sticks at the edge, eating leaves from the plant. He made another attempt to enter the house but loud squeals and rustling followed and he returned to the ironweed plant and was still eating when observations were halted. In another instance, squeals and rustling indicated that the occupant and intruder were in combat.

Although home ranges may overlap to some extent, intraspecific intolerance tends to maintain a certain minimum interval between houses. The arrangement of twelve houses along a hedge row 1170 feet long is diagrammatically represented in Figure 2. The average interval was 78.5 feet (minimum 42; maximum 171). The habitat was uniform. Home ranges probably overlap somewhat, and the spacing is the expression of the need for an otherwise unoccupied area in which there is sufficient space to live. Because individuals tend to fight whenever they meet, there is probably a psychological tendency for sequestration which results in spacing of houses and reduces social contact thereby avoiding a depletion of energy that would be detrimental to the population. Whereas condition of the hedge row determines whether or not it will be inhabited by woodrats, length determines the number of occupants. The spacing of houses in a hedge row must be attributed to something other than restriction of sites because the number of sites available always exceeds the number that are in use. Although rock outcrops situated in areas of uniform habitat have not been observed to the extent that hedge rows have, a similar spacing seems to exist and the sites available for houses always exceed the actual number found. This behavior pattern limits the number of houses and is probably advantageous to the species through preventing overcrowding and possible critical depletion of the food supply.

Eleven of the young that weighed 100 grams or less when originally captured and were presumably still living at the mothers' houses, were recaptured repeatedly over periods of weeks or months, providing a limited amount of information regarding dispersal. They followed no definite pattern. In seven instances (five males and two females) the young stayed on at the house beyond the age when they were completely independent of the female. In at least two instances the female was known to have moved away while the young remained. One female shifted to a house 58 feet from the one where she had reared her litter of two, and was accompanied by the young male, while the young female stayed on in possession of the maternal house. Two months later this young female was caught at a house 90 feet away, and an adult male was in possession of her former house. One young male shifted to a house 220 feet from his original home and remained there several months, but was recaptured once back at the original location. Another male made a series of moves over a period of weeks and finally settled in a house 490 feet from his first home. One male who stayed in the maternal house all summer, and reached adult size there, later moved several times, and was last recorded 900 feet away. One young female shifted 110 feet. In several instances juveniles appeared abruptly in houses known to have been unoccupied previously, and some of these houses were in poor repair. These young had wandered from their maternal houses, for unknown reasons. On one occasion a young woodrat was caught in a mouse trap set in a meadow, a habitat into which adult woodrats would scarcely be expected to venture.

Feeding

Rainey (1956) has listed 31 food plants that are used by the woodrat in northeastern Kansas. He has emphasized that each rat usually obtains its food from plants growing in the immediate vicinity of its house, and that individuals thus differ greatly in their feeding, according to the local vegetation. Therefore, with a sufficiently large number of observations, the list of food plants might be greatly expanded, to include most of the local flora, with the exception of the relatively few kinds that have developed strongly repellent properties rendering them unpalatable to herbivores in general.

At the quarry where one or more woodrats usually lived beneath metal strips, as described previously (under the heading of "Commensals"), the situation seemed to be especially favorable, despite the fact that the metal offered no insulation from extremes of heat in summer and cold in winter. Perhaps the rat had an alternative nest among nearby boulders, to use when temperature was unendurable beneath the metal.

The rat itself, the stored food, and other details of its home life, could be observed with a minimum of disturbance by raising one side of the metal strip momentarily, then carefully lowering it into place. The following observations made in the summer and autumn of 1948 give some idea of the range of food plants stored at any one time and the change as the season progresses.

July 12: Bundles of leaves of carrion-flower (Smilax herbacea); 15 green pods of honey locust (Gleditsia triacanthos) with seeds eaten out; several green fruits of osage orange (Maclura pomifera), and several seeds of coffee-tree (Gymnocladus dioica).

July 24: Bundles of green leaves of osage orange and carrion-flower; many pods of honey locust.

August 30: Three large clusters of the fruits of pokeberry (Phytolacca americana).