Genetic variation and relatedness in grizzly bears in the Prudhoe Bay region and adjacent areas in northern Alaska

The Prudhoe Bay region of northern Alaska has large oil fields and hunting on adjacent lands, and there are concerns about potential effects on grizzly bears (Ursus arctos) in this region. Because effects on grizzly bear populations may include loss of genetic variation, we assessed the genetic variation and family relationships among grizzly bears in this region as part of a long-term research and monitoring project. We determined genotypes at 14 microsatellite DNA loci for 78 bears from the Prudhoe Bay region from samples collected 1990-2002. The genetic data identified one or both potential parents of 33 offspring. Potential parent-offspring and siblings had pair-wise relatedness indices ofapproximately 0.5, as expected. The entire sample of related and unrelated bears in the Prudhoe Bay region had a mean pair-wise relatedness index of approximately zero. Approximately 5.3% of the bears had relatedness indices within the range of first-order relatives (parent-offspring or siblings). Genetic differentiation is low (F-st = 0.0225) among the bears in the Prudhoe Bay region and neighboring areas of the western Brooks Range and the Arctic National Wildlife Refuge. Bears in the Prudhoe Bay region have a high level of genetic variation relative to some other areas in North America. High genetic variation and low relatedness among individual bears in the Prudhoe Bay region are probably maintained by a stable population size with gene flow across the North Slope of Alaska. Our data indicate that reduction of genetic variation in the grizzly bears in the Prudhoe Bay region is not presently a management concern.