Various interpretations of the Craighead team data on Yellowstone grizzly bears (Ursus arctos horribilis) are reviewed. The Craigheads continue to favor a noncompensatory model that gives the greatest likelihood of population extinction with an increased mortality rate. McCullough (1981) found that recruitment of cubs and survivorship of juveniles were influenced by adult population size. Stringham (1983) reached most of the same conclusions by different methods. McCullough (1981), Stringham (1983), and Shaffer (1978, 1983) all reported negative relationships between adult population size (or adult males only) and percent of females producing litters and mean litter size. Time lags in the density-dependent effect of adults on cub recruitment were treated by Avrin (1976) with slightly different results. All authors have emphasized the susceptibility of grizzly bear populations to overexploitation, although the impact varies with model assumptions. Shaffer (1978, 1983) examined stochastic variables as they influence minimum viable population size. A congruence analysis was done for the McCullough (1981) model in which parameters were run in model simulations to test model responses to observed results for the years of the Craighead study. This analysis reaffirmed the oscillatory behavior of the population and showed that oscillatory behavior decreased as the adult mortality rate increased. Great fluctuations in population parameters make assessment of the current status of the population difficult. An alternate strategy of long-term population monitoring and management based on a systematized aerial count of minimum unduplicated bears is proposed.
- Volume 6
- Issue
- Pages 21-32
- Publication Date 1 January 1986
- DOI 10.2307/3872802
- File Size 461.17 KB
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