While wild polar bear populations continue to face threats from melting polar ice as a result of global warming, captive polar bear populations in North America are also in a state of decline, and we are at a critical point in our efforts to maintain sustainable captive populations. This is due in part to an aging captive population and a shrinking pool of reproductively viable animals. Additionally, even though nearly all females of reproductive age are paired for breeding, only ∼10% of these females produce cubs. The North American polar bear Species Survival Plan is currently focused on morbidity/mortality reviews, understanding and improving reproductive health and viability, and intensified collaborations with field research scientists to help with the study and understanding of wild and captive polar bear populations.
Scientists at the Center for Conservation and Research of Endangered Wildlife at the Cincinnati Zoo & Botanical Garden have monitored 60 captive polar bears from 30 zoological institutions throughout North America. Regular non-invasive fecal steroid metabolite monitoring has documented seasonal shifts in testosterone concentrations in adult male polar bears, whereas progesterone and testosterone metabolites have provided insight into ovarian activity, pregnancy and pseudopregnancy of females.1,4 Differential analyses of fecal proteins have uncovered several specific peptides excreted in higher concentrations by pregnant versus pseudopregnant females and current research aims to confirm their use as diagnostic biomarkers of pregnancy.2 A rapid, field-friendly method of semen collection has been validated for this species and sperm cryopreservation trials resulted in the establishment of a polar bear sperm bank, preserving valuable genetics. Endeavors investigating the use of exogenous hormones in females indicate that ovulation may be induced for scheduled artificial insemination procedures; however, no cubs have been produced to date.3
1. Curry E, Roth TL, MacKinnon KM, Stoops MA. Factors influencing annual fecal testosterone metabolite profiles in captive male polar bears (Ursus maritimus). Reprod Domest Anim. 2012; 47 Suppl 6:222–5.
2. Curry E, Stoops MA, Roth TL. Non-invasive detection of candidate pregnancy protein biomarkers in the feces of captive polar bears (Ursus maritimus). Theriogenology. 2012; 78(2):308–14.
3. Curry E, Wyatt J, Sorel LJ, MacKinnon KM, Roth TL. Ovulation induction and artificial insemination of a captive polar bear (Ursus maritimus) using fresh semen. J Zoo Wildl Med. 2014; 45(3):645–9.
4. Stoops MA, MacKinnon KM, Roth TL. Longitudinal fecal hormone analysis for monitoring reproductive activity in the female polar bear (Ursus maritimus). Theriogenology. 2012; 78(9):1977–8.