|
Journal Publications
Philip D. McLoughlin, Mitchell K. Taylor, H.
Dean Cluff, Robert J. Gau, Robert Mulders, Ray L. Case, Stan Boutin, and
François Messier. Demography of barren-ground grizzly bears. Can. J. Zool.
81: 294–301 (2003)
(PDF =
193 KB)
Abstract:
Between May 1995 and June 1999, we
equipped 81 barren-ground grizzly bears (Ursus arctos) with satellite radio
collars within a study area of 235 000 km2, centred 400 km northeast of
Yellowknife, Northwest Territories, Canada. We used data from radiotelemetry
to estimate survival rates, reproductive parameters, and the finite rate of
increase of the population (λ). The annual survival rate of adult females
was estimated at 0.979 (95% confidence intervals (CI) = 0.955–0.998), while
the survival rate of adult males was 0.986 (95% CI = 0.942–1.0). The cub
survival rate was 0.737 (95% CI = 0.600–0.844) and the yearling survival
rate was 0.683 (95% CI = 0.514–0.821). Cub litter size averaged 2.23 (SE =
0.13, n = 35), while yearling litter size decreased to a mean of 1.86 (SE =
0.12, n = 35). The mean litter size of females with 2-year-olds was 1.85 (SE
= 0.15, n = 20). The mean birth interval was 2.8 years (SE = 0.3 years,
n =
17). The mean reproductive interval, which is calculated by excluding the
loss of whole litters from the sample, was 3.9 years (SE = 0.4 years, n =
9). Mean litter size divided by mean birth interval yielded an annual
natality rate of 0.81 cubs per adult female per year. The mean age at first
parturition was 8.1 years (SE = 0.5 years, n = 10). We believe the
population to be currently stable or slightly increasing (λ = 1.033, 95% CI
= 1.008–1.064). |
