The sexual cycle of the male long-tailed weasel (Mustela frenata)

1 litter a year usually in April. Young male does not reach adult weight in 1st year and is immature; young female will mature and be mated in 1st year by older male. By early November young male distinguishable only on weight of baculum, but in early spring all males show rapid changes in genitalia, spermatogenesis begins in March. Ap-July testes max size, 7-8 times seize of regressed testes. Regression Aug-Oct. Oct, begin molt to white in northern populations, and white coated animals always sexually inactive.

Author P. L. Wright
Year 1947
Secondary title Journal of Mammalogy
Volume 28
Number 4
Pages 343-352