Population Fragmentation of Grizzly Bears in Southeastern British Columbia, Canada

Proctor, Michael; McLellan, Bruce; Strobeck, Curtis

The distribution of grizzly bears (Ursus arctos) at the southern edge of their North 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 2 on 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 questions of dispersal and fragmentation across a potential fracture. Our data suggests that female movement across the human transportation corridor has been negligible and male movement has been reduced from historic levels.

Population Fragmentation of Grizzly Bears in Southeastern British Columbia, Canada

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