Comparative endocrine investigations in three bear species based on urinary steroid metabolites and volatiles

In order to improve breeding of in situ populations of bears, a comprehensive study of reproductive physiology in Brown (Ursus arctos), Spectacled (Tremarctos ornatus) and Giant panda bears (Ailuropoda melanoleuca) was performed. The objective was to perform non-invasive analyses of urinary and fecal steroid metabolites. In addition, we investigated the presence of reproduction-related urinary volatile substances of these bears that might trigger the reproductive behavior. Urinary estrogen concentrations, routinely used to monitor follicular activity in Giant panda, were inappropriate for monitoring follicular activity in Spectacled bear. In addition, no estrogen peak related to mating activity was observed in Brown bear. Further contrasting Giant panda, although urinary pregnanediol analyses failed to indicate luteal activity in either Spectacled or Brown bears, urinary (Spectacled bear) and fecal (Brown bear) concentrations of progesterone were an appropriate indicator of luteal activity. The Giant panda had volatile components (medium-chain fatty acids) in their urine that increased simultaneously with the seasonal increase of estrogens. These fatty acids were also detected in the Brown during estrus and Spectacled bear. Further studies on the behavioral relevance of these fatty acids are required to determine if they are pheromones.