Observations of recognizable brown bears (Ursus arctos) at McNeil River State Game Sanctuary (MRSGS) during 1963-91 provided long-term data on population size, sex and age composition, reproductive success, and survival rates. Bears using MRSGS increased from 66 (SE = 5.8) during 1969-84 to 113 (SE = 8.5) during 1987-91. Adult sex ratio averaged 121 males/100 females. This reflected a low exploitation rate and greater seasonal movements of male bears. Adult survival rates averaged 0.94 for males and 0.93 for females. Since 1963, 31% of 168 cubs disappeared between 0.5 and 1.5 years of age. Kaplan-Meier estimates of summer survival rates were 0.67 for cubs and 0.89 for yearlings. Twenty females, observed for a total of 242 bear-years, raised 83 yearlings in 47 litters. Lifetime recruitment for 11 females observed from sexual maturity to presumed death averaged 2 (range 0-8) yearlings. Despite the high ratio of adult males to females and increased population size, we did not detect a density-dependent suppression of cub production or survival.
- Volume 9
- Issue
- Pages 283-293
- Publication Date 1 January 1994
- DOI 10.2307/3872712
- File Size 430.67 KB
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