Document Type

Dissertation

Abstract

Polar bears (Ursus maritimus) are threatened by climate change in the wild, and experience poor to moderate reproductive success in zoos. If current climate change trends continue, the species is unlikely to persist in Alaska by the end of the 21st century due to the loss of sea ice habitat. Polar bears are a seasonally polyestrous species that exhibit embryonic diapause and pseudopregnancies, making characterization of female reproductive status difficult. The purpose of this dissertation project was to investigate a suite of understudied hormones associated with reproduction, with the goal of improving reproductive monitoring in zoo-housed and wild polar bears, and emphasizing hormones that may help predict reproductive success. I investigated the long-term fecal excretion of dehydroepiandrosterone sulfate (DHEAS) and the glucocorticoid corticosterone in the feces of female zoo-housed polar bears, and a cross-section of serum samples from wild and zoo-housed female polar bears for DHEA, the active form of DHEAS, the reproductive steroid testosterone, and cortisol using enzyme immunoassay techniques. I found that although short-term increases in DHEAS concentrations were associated with estrus, chronically elevated DHEAS concentrations, particularly after breeding, were associated with reproductive failure. Elevated fecal corticosterone concentrations, even before breeding, were also associated with reproductive failure. Significant correlations between DHEA/DHEAS, cortisol/corticosterone, and testosterone suggest that three hormones interact with each other to influence reproductive success. Although the role of DHEA/DHEAS in reproduction remains unclear, including it along with corticosterone and traditionally monitored reproductive hormones could improve reproductive monitoring and predictions of pregnancy success in polar bears for both zoo and wildlife managers.

Publication Date

5-17-2023

Handle

http://hdl.handle.net/11122/13231

Download

Share

COinS