Using Genetics to Verify Sex of Harvested Polar Bears: Management Implications

Schliebe, Scott; Evans, Thomas; Fishbach, Anthony; Cronin, Matthew

Polar bear (Ursus maritimus) occur at low densities in the southern Beaufort, Chukchi, and Bering seas of Alaska. Populations have a low intrinsic rate of increase. Therefore, excessive harvest of adult females may result in population declines. Accurate sexing of harvested bears is important to make informed management decisions. We determined sex of harvested bears by analyzing chromosomal DNA to assess accuracy of reported sex. Sex was incorrectly 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 of bears varied by sex and age class. A bootstrap resampling analysis determined that sub-adult females had a greater chance of being incorrectly sexed than adult females and that only sub-adults had a bias toward misreporting females as males. At the current harvest level and estimated population size, the misidentification of sex does not result in an overharvest of females. 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 teaching morphologic identification techniques, requiring that bacula of males be presented upon tagging, and conducting genetic analysis of harvested polar bears when sex is otherwise uncertain.

Using Genetics to Verify Sex of Harvested Polar Bears: Management Implications

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