Grizzly Ursus arctos and black bear U. americanus densities in the interior mountains of North America
Garth Mowat, Douglas C. Heard, Dale R. Seip, Kim G. Poole, Gord Stenhouse & David W. Paetkau
Mowat, G., Heard, D.C., Seip, D.R., Poole, K.G., Stenhouse, G. & Paetkau, D.W. 2004: Grizzly Ursus arctos and black bear U. americanus densities in the interior mountains of North America. - Wildl. Biol. 11: 31-48.
We collected hair samples from bears and used microsatellite genotyping to identify individual bears on three study areas near the Canadian Rocky Mountains. We estimated density of grizzly bears Ursus arctos in eight different ecosystems across five study areas, including the reanalysis of two previously published data sets. We also estimated black bear U. americanus density for two ecosystems in one study area. Grizzly bear density was lowest in boreal and subboreal plateau areas, moderate in the Rocky Mountain east slopes and highest in the Rocky Mountain west slopes. Presumably these gross differences are related to ecosystem productivity. In the Rocky Mountain west slopes, grizzly bear density was lower in populations that were partially isolated from the continuous bear population to the north. Presumably, these differences have more to do with human impacts on habitat and survival than ecosystem productivity, because productivity in partially isolated areas was similar to productivity in adjacent continuous populations. We show that large differences in bear density occur down to the ecoregion scale; broader ecosystem classes such as Banci’s (1991) grizzly bear zones, ecoprovinces or ecozones would include areas with major differences in density and are therefore too coarse a scale at which to predict grizzly bear density. There appears to be little movement across ecoregion boundaries further suggesting that this may be an appropriate scale at which to extrapolate density. Differences in density across finer-scale ecosystems are likely due to seasonal movements and not population level differences in density. Average bear movements were longer in less productive ecosystems. Female grizzly bears did not appear to leave their home ranges to fish for salmon Oncorhynchus spp., and extra-territorial movements by males appeared to be rare, in both ecosystems which supported spawning salmon.
Key words: carrying capacity, closure, ecosystems, movements, population size, Ursus americanus, Ursus arctos
Garth Mowat, Aurora Wildlife Research, RR 1, Site 14, Comp 8, Crescent Valley, BC V0G 1H0, Canada - e-mail: email@example.com
Douglas C. Heard, British Columbia Ministry of Water, Land, and Air Protection, Fish and Wildlife Branch, Omineca Subregion, 1011 4th Ave., Prince George, BC V2L 3H9, Canada - e-mail: firstname.lastname@example.org
Dale R. Seip, British Columbia Ministry of Forests, 1011 4th Ave., Prince George, BC V2L 3H9, Canada - e-mail: email@example.com
Kim G. Poole, Aurora Wildlife Research, 2305 Annable Rd., Nelson, BC V1L 6K4, Canada - e-mail: firstname.lastname@example.org
Gord Stenhouse, Alberta Sustainable Resource Development, Fish and Wildlife Division, Box 6330, Hinton, Alberta T7V 1X6, Canada - e-mail: email@example.com
D. W. Paetkau, Wildlife Genetics International, Box 274, Nelson, BC V1L 5P9, Canada - e-mail: firstname.lastname@example.org
Corresponding author: Garth Mowat
Received 30 December 2002, accepted 3 February 2004
Associate Editor: Joel Berger