Reproduction in the Mountain Cottontail Rabbit in Oregon

• Published in: The Journal of wildlife management 1971-10, Vol.35 (4), p.605-613
• Main Authors: Powers, Roger A., Verts, B. J.
• Format: Article
• Language: English
• Subjects: Breeding; Breeding seasons; Embryos; Litter size; Rabbits; Rats; Reproduction; Spermatozoa; Testes; Wildlife damage management
• ISSN: 0022-541X; 1937-2817
• DOI: 10.2307/3799763

Reproductive tracts of 269 mountain cottontail rabbits (Sylvilagus nuttallii) collected in Deschutes and Jefferson counties, Oregon, between May 28, 1968, and August 28, 1969, were excised and examined. Sex ratios of specimens collected by shooting, and of embryos more than 25 mm in length, were not significantly different from 1:1. Adult males appeared to be in breeding condition in the interval January-July. Juvenile males apparently did not attain breeding condition in the year of their birth. Adult females began to breed in late February and ceased to breed in early July in 1969. Most adult females probably produced four litters in 1969; some may have produced five litters. Thirty-one adult females shed an average of 5.0 ± 0.2 ova per pregnancy, of which an average of 4.6 ± 0.2 were implanted, and an average of 4.3 ± 0.1 were viable embryos at the time of collection. Only 1 of 15 juveniles collected during the breeding season was pregnant. Productivity of the population of mountain cottontails in central Oregon was considerably less than that reported for eastern cottontails (Sylvilagus floridanus) in Missouri or Oregon but apparently was considerably greater than heretofore thought possible for the species.