Abstract
Nineteen wild male Siberian weasels (Mustela sibirica coreana), collected from August 1997 to April 2011 in Tsushima Islands, were used for this study. The testes and baculum were measured, and testicular samples were autopsied and observed histologically. In the subadult, testes size and seminiferous tubule diameter tended to increase rapidly from November, peaking around February. In the adult, testes size and seminiferous tubule diameter tended to be large from February to June, and small from September to around January. Because young animals contain spermatozoa in the epididymis after April, they appear to attain sexual maturity around April of the year after birth. The baculum of the adult of this species has developed a hook-shaped distal tip and spatulate base.
