Testicular activity and epididymal sperm collection from American black bears in November

Abstract: Prolonged reproductive behavior of American black bears (Ursus americanus) has been reported in the southeastern United States compared with other regions, but functional spermatogenesis or potential fertility has not previously been described for these bears. Additionally, methods for gamete collection are only in early stages of development for ursids. Testicles were collected from 29 post-pubertal legally hunter-killed black bears in eastern North Carolina, USA, in November 2016. Active spermatogenesis was identified in 48.3% (14/29) of bears via histology. Epididymal sperm collection was attempted via mincing (n = 29), vas deferens flush (n = 24), and percutaneous aspiration (n = 5). Epididymal mincing identified sperm in 78.6%, and vas flush in 53.8%, of bears with spermatogenesis on histology. Percutaneous aspiration was unsuccessful. These findings provide evidence that male bears may maintain reproductive capabilities into the late autumn in this region, and that under the conditions of this study, sperm can be collected via epididymal mincing or vas deferens flush, but not percutaneous aspiration.