Dynamics of a grizzly bear population during a period of industrial resource extraction. III. Natality and rate of increase

Abstract

Reproductive parameters and rate of increase were estimated for a grizzly bear (Ursus arctos) population in southeastern British Columbia during a period of timber harvest and gas exploration, 1979–1987.I hypothesized that these activities would be detrimental to the population and predicted a negative rate of increase. There was an average of 2.26 cubs in 31 litters. The average of nine interbirth intervals was 2.67 years, and the average age at which five females produced their first litter was 6 years. The population's annual reproductive rate calculated by three methods averaged 0.86 cubs per adult female. By iteration of the Lotka equation, the best estimate of the exponential rate of increase was 0.081. Industrial activities did not appear to have a significant detrimental effect on the grizzly bear population in the Flathead Valley during the period of study but the roads built provided easy access for hunters and poachers.