Using genetics to verify sex of harvested polar bears: management implications

Polar bear (Ursus maritimus) occur at low densities in the southern Beaufor t, Chukchi, and Bering seas of Alaska. Populations have a low intrinsic rat e of increase. Therefore, excessive harvest of adult females may result in population declines. Accurate sexing of harvested bears is important to mak e informed management decisions. We determined sex of harvested bears by an alyzing chromosomal DNA to assess accuracy of reported sex. Sex was incorre ctly determined for 19 of 139 (13.7%) bears. More incorrectly sexed animals were recorded as males when they were Females, resulting in an overall 12% underestimate of females in the harvest. Probability of incorrect sexing o f bears varied by sex and age class. A bootstrap resampling analysis determ ined that sub-adult females had a greater chance of being incorrectly sexed than adult females and that only sub-adults had a bias toward mis reportin g females as males. At the current harvest level and estimated population s ize, the misidentification of sex does not result in an overharvest of fema les. However, if harvest levels increase or population levels decline, male bias in reporting could result in an overharvest of females. We recommend minimizing sex misidentification by reaching morphologic identification tec hniques, requiring that bacula of males be presented upon tagging, and cond ucting genetic analysis of harvested polar bears when sex is otherwise unce rtain.