This year’s International Society of Wildlife Endocrinology Conference was held in Corbett National Park, India, on 6-9 November 2023. The AnthroBear project results on male brown bears reproductive glands were presented as a poster in the Reproductive Function Section, among reports on reproductive biology of several species, including okapi (Okapi johnstoni), large spotted genet (Genetta tigrina), bontebok (Damaliscus pygargus), fin whale (Balaenoptera physalus), blue whale (Balaenoptera musculus), and mugger crocodile (Crocodylus palustris).
The brown bear is a seasonal breeder with a mating season occurring in spring, and the timing of active spermatogenesis well coincides with the high reproductive activity. However, there are reports on mating taking place also in Autumn. Some studies also indicated that the male reproductivity generally lasts longer than the female receptivity. Maintenance of spermatogenesis requires high testosterone. However, males are reported to produce spermatozoa actively despite low plasma testosterone concentrations and out of mating season. Within the project, we aimed to determine the factors that regulate testosterone production and contribute to differences in spermatogenetic activity, morphological, histological, and endocrinological changes. We measured brown bear males’ testicular mass, volume, body mass, and testosterone concentrations in testicular tissue (using LCMS/MS technique) and hair samples (using EIA technique). Additionally, immunohistochemical methods were used to investigate the localization and immunohistochemical staining intensity of the 11β-hydroxysteroid dehydrogenase and androgen receptor (AR). We observed significantly higher seminiferous tubules diameter in spring, as well as an increase in testicular mass and volume in adult males. Our ongoing analyses will investigate the relation of spermatogenesis, testosterone biosynthesis, and other factors contributing to testicular activity in brown bear.