Seven females known to be pregnant or lactating were not observed to move more than 100 feet away from their centers of activity. Their nests were never found. At the same time the males were moving over much larger areas. The cottontail is most active in the evening or early morning. Of those for which time of capture in live-traps was known 70 per cent were captured in the evening between dusk and 11:00 P.M., 10 per cent were captured between 11:00 P.M. and dawn, and 20 per cent were captured after dawn. Nocturnal rodents and carnivores often stole bait in the night; the percentage of capture of cottontails after dawn might have been larger had bait remained in all the traps. Except for those flushed, cottontails were seldom seen by day. In walks through the study area approximately three times as many cottontails were flushed at night as in the daytime. On cloudy days cottontails were active longer than on bright days. On dark nights more cottontails were captured in live-traps between 11:00 P.M. and dawn than on bright moonlight nights. Cottontails were more active (as determined by trap success and frequency of observation) at temperatures between 0 deg. F. and 33 deg. F. than at temperatures between 33 deg. F. and 55 deg. F. Activity of the cottontail increased as the temperature of the air decreased. Activity increased in proportion to the percentage of ground covered by snow. Activity of the cottontail decreased as precipitation increased; there was less activity in rain than in snow and less activity in wet snow than in dry snow. Activity did not vary significantly with depth of snow until snow was more than 8 inches deep, when activity decreased abruptly. The average of the longest distance traveled between captures for cottontails whose entire home ranges were thought to have been sampled was 900 feet for males and 684 feet for females. The average of the maximum distance across the home range for cottontails whose home range had been thoroughly sampled was 1019 feet for males, and 936 feet for females. The home range is used by the cottontail in different ways, depending on the needs of the individual and the condition of the habitat. In uniform habitat the home range is roughly circular and is used most near its center and least toward its periphery. The entire home range is traversed every four or five days. The center of the home range has been called the "center of activity" (Connell, 1954). In habitat of alternating woodland and grassland, such as that on the University of Kansas Natural History Reservation, two centers of activity often developed in the home range of a cottontail, at opposite edges of a tract of woodland. The individual concentrated its movements near one center for three to five days then moved to the other center. Pursuit by a predator, random movement, or other cause may be responsible for shift from one edge to another. PLATE 45