Post by warsaw on Nov 6, 2011 1:36:48 GMT -9
A search for evidence in a northern
alpine ecosystem
Lambert Koizumi, Catherine1 (cathlambert@ualberta.ca), A. E. Derocher1
1 Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9
Grizzly bears (Ursus arctos) may exhibit varying degrees of carnivory depending on various factors, including
body mass, litter size, population density, and prey availability. To assess whether grizzly bears in the Richardson
Mountains, Canada, prey and feed on a Dall sheep (Ovis dalli dalli) population, we investigated the habitat use
and home range overlap of the two populations, stable isotope ratios of grizzly bears and several
food sources, and interviewed 23 Gwich’in and Inuvialuit elders and harvesters on their traditional ecological
knowledge. Spatial analyses revealed a substantial overlap between the two populations, with a third of core areas
intensively used by Dall sheep also used intensively by 6 of the 15 collared grizzly bears. Stable isotope analyses
support the hypothesis that grizzly bears in the area have a high level of carnivory, although other prey like moose
(Alces alces) and caribou (Rangifer tarandus) have an isotopic signature close to Dall sheep; so the species consumed
may not be distinguished without further analyses. Knowledge shared by Gwich’in and Inuvialuit interviewees
bring mixed evidence and varied among them. Some participants mentioned that Dall sheep are hard to catch
and believed grizzly bears rather feed on berries, arctic ground squirrels (Spermophyllus parryii), and fish. Other
participants were convinced that the bears commonly rely on Dall sheep and reported events of both scavenging
and predation. Based on the carnivory level of grizzly bears in this ecosystem, on their overlap with Dall sheep
home range, and on testimonies by aboriginal interviewees, our research supports the premise that Dall sheep are
indeed part of the grizzly bears’ diet.
alpine ecosystem
Lambert Koizumi, Catherine1 (cathlambert@ualberta.ca), A. E. Derocher1
1 Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9
Grizzly bears (Ursus arctos) may exhibit varying degrees of carnivory depending on various factors, including
body mass, litter size, population density, and prey availability. To assess whether grizzly bears in the Richardson
Mountains, Canada, prey and feed on a Dall sheep (Ovis dalli dalli) population, we investigated the habitat use
and home range overlap of the two populations, stable isotope ratios of grizzly bears and several
food sources, and interviewed 23 Gwich’in and Inuvialuit elders and harvesters on their traditional ecological
knowledge. Spatial analyses revealed a substantial overlap between the two populations, with a third of core areas
intensively used by Dall sheep also used intensively by 6 of the 15 collared grizzly bears. Stable isotope analyses
support the hypothesis that grizzly bears in the area have a high level of carnivory, although other prey like moose
(Alces alces) and caribou (Rangifer tarandus) have an isotopic signature close to Dall sheep; so the species consumed
may not be distinguished without further analyses. Knowledge shared by Gwich’in and Inuvialuit interviewees
bring mixed evidence and varied among them. Some participants mentioned that Dall sheep are hard to catch
and believed grizzly bears rather feed on berries, arctic ground squirrels (Spermophyllus parryii), and fish. Other
participants were convinced that the bears commonly rely on Dall sheep and reported events of both scavenging
and predation. Based on the carnivory level of grizzly bears in this ecosystem, on their overlap with Dall sheep
home range, and on testimonies by aboriginal interviewees, our research supports the premise that Dall sheep are
indeed part of the grizzly bears’ diet.