Pelage Stages in the Cottontail Rabbit

Abstract

A number of criteria have been employed to determine the age of cottontail rabbits. These include weight measurements, total length measurements, condition of the hymen in females, size of male genitalia, and ossification of epiphyseal cartilage in the bones of the forefeet. Having undertaken a study of reproduction in the cottontail rabbit, Sylvilagus floridanus mearnsi , in Ohio in 1952, I was faced with the problem of accurately aging rabbits in the field. The above methods had the disadvantage of either being impractical for field use or of not being useful in accurately aging young rabbits late in the breeding season. This study was made possible through financial assistance from the Ohio Cooperative Wildlife Research Unit and a grant from the Wildlife Management Institute. For cooperation and assistance during the study I am greatly indebted to many of the faculty and graduate students in zoology at Ohio State University, and to personnel of the Ohio Division of Wildlife, whose names are too numerous to mention here. In particular I should like to acknowledge the invaluable advice and criticism afforded me throughout the study by Dr. Eugene H. Dustman, Leader of the Research Unit. A portion of these data was presented at the 16th Midwest Wildlife Conference. The pelage stages of cottontails have not been adequately described. Nelson (1909) recognized three distinct pelage stages apparently common to all North American hares and rabbits. These were designated as juvenal, postjuvenal and adult pelage. He described Sylvilagus as a genus having only one annual molt. He did recognize that species in the genus Lepus and subgenus Brachylagus experienced two molts annually. Dalke et al. (1942) concluded that adult cottontails experienced a continual molt over a nine-month period, from March to November. Three constituents of the dorsal pelage of cottontail rabbits have been described …