Population fragmentation of grizzly bears in southeastern British Columbia, Canada

The distribution of grizzly bears (Ursus arctos) at the southern edge of theirNorth American range includes 5 mountain peninsulas extending from the contiguous northern distribution. In several cases, these peninsulas cross into the conterminous United States. The long-term survival of these populations may depend on the retention of demographic links to the contiguous northern distribution. We investigated whether a major transportation corridor fragments the population of grizzly bears in the Central Rocky Mountain Ecosystem. Using non-invasively obtained hair samples collected in 1996-99, we generated 15-locus microsatellite genotypes for 220 bears, 120 to the north, 98 to the south, and 2on both sides of the highway corridor. We used a population assignment test with a related genetic distance measure to determine the amount of gender-specific connectivity between areas directly north and south of the highway corridor. We found evidence of 1 female and 3 male grizzly bears moving across BC (British Columbia) Highway (Hwy) 3 using the population assignment test, and we DNA-captured 2 males on both sides of the highway. Our use of individually based genetic measures, coupled with a large sample of bears from 2 immediately adjacent populations, allowed us to efficiently examine the ecological questionsof dispersal and fragmentation across a potential fracture. Our data suggeststhat female movement across the human transportation corridor has been negligible and male movement has been reduced from historic levels.