Biology of Penned Cottontail Rabbits

Abstract

Cottontail rabbits (Sylvilagus floridanus) were raised in 25x 60-foot game-bird rearing pens during 1961-63 at Poynette, Wisconsin. Conception dates of first litters were less synchronized than those of Missouri cottontails. Nests were constructed from a week before to the day of parturition. Usually a new nest was built for each litter. Maternal care to young seemed to be limited to nursing and covering the nest after feeding. A mean of 2.9 litters per summer with an average of 4.9 young per litter was obtained in the study. Forty-four percent of the young died in their first month. Myiasis by the flesh fly (Wohlfahrtia vigil) was the most serious mortality factor during June and July. Adults had an average monthly mortality rate of 2.8 percent. Summer was the period of highest adult mortality. This paper reports on nesting, reproduction, and mortality of cottontail rabbits reared in 25x 60-foot pens at the Wisconsin Conservation Department Game and Experimental Farm, Poynette, during the summers of 1961-63. Cottontail rabbits have been raised in captivity in a variety of pen sizes and with varying degrees of success (Gerstell 1935, 1937; Stuber 1938; Dalke 1942; Atzenhoefer and Martin 1949; Sheffer 1957a, 1957b, 1958; Grant 1959; Marsden and Conaway 1963). Reproduction in my study, although probably lower than in the wild, was sufficiently high to provide animals for experimental purposes. Survival was probably higher in the pens than is normal in the wild. Information for this report was obtained while I was developing a technique for marking mammals with calcium-45 (Rongstad 1965). For advice throughout the course of this study, I am indebted to R. A. McCabe, J. J. Hickey, and L. B. Keith. MATERIALS AND METHODS Sixty-six pens arranged in three rows were used. The main section of each pen was 25 x 60 x 5 feet and was connected to a brooder house (about 12 x 8 feet) by a smaller pen (12 x 6 x 5 feet) for a total area of 1,674 square feet (0.038 acre) (Fig. 1). The sides of the pens were 1-inch-mesh poultry wire buried in the ground about 12 inches, and the tops were covered with 2-inch-mesh poultry netting. Each pen contained a good growth of quack grass (Agropyron repens) or Kentucky bluegrass (Poa pratensis), or a combination of these. The pens originally were made for rearing pheasants (Phasianus colchicus), and were modified only to make the doors rabbit-proof. The bottom 6-12 inches of the pen should have been covered with boards or a finer-mesh wire, since young that had just left their nest could get through the 1-inch mesh. One shelter was constructed for each adult in the pen. A 2-foot section of snow fence bent into a U shape with the open side down, and covered with a generous thatch of hay or straw, was durable and simple to construct. Shelters were used at all times of the year but were probably most necessary in winter. The brooder houses were used little as loafing places unless boxes or other objects were in the house for the animals to hide under or