Dispersal and Survival of Subadult Black Bears from the Kenai Peninsula, Alaska

Schwartz, Charles; Franzmann, Albert

Movements, dispersal, and survival rates of subadult black bears (Ursus americanus) are poorly documented in North America. Consequently, we studied timing of family breakup, post-breakup range use, timing and distances of dispersal, and survival of subadult black bears from 2 areas on the Kenai Peninsula, Alaska. One study area was burned in 1947 and the other in 1969, representing different aged stands of boreal forest. Timing of family breakup was not different between the 2 areas (P = 0.86), so data were pooled. Among 28 family groups, no yearlings separated from their mothers by 7 May, but all had by 25 June. Of 28 family groups, 26 remained separated, but 2 reunited. Timing of family separation did not differ (P = 0.79) for females producing their first litters versus those producing subsequent litters. Likewise, litter size did not influence timing of separation (P = 0.20), although there was a tendency for large litters to remain together longer. Of 51 subadults, all males dispersed; whereas 97% of females remained in the areas occupied by their mothers. Only 14-17% of subadult males, but 30-48% of subadult females, survived to adulthood. Behavioral differences between subadult male and female black bears must be considered when managing heavily harvested populations or those populations that are geographically isolated. In continuous habitat, local overharvest of females can reduce sustained yields; whereas in fragmented habitats an adequate reservoir of females must be maintained to ensure population stability.

Dispersal and Survival of Subadult Black Bears from the Kenai Peninsula, Alaska

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