| Pease, Mattson | Craig M., David J. | Demography of the Yellowstone grizzly bears. | 1999 | Ecology 80(3):957-975 |
This paper contrasts with others that estimate a more optimistic growth rate for the Yellowstone grizzly bear population (e.g., Eberhardt et al. 1994, Eberhardt 1995, Boyce 1995).
Excerpts from the abstract:
"We undertook a demographic analysis of the Yellowstone grizzly bears (Ursus arctos) to identify critical environmental factors controlling grizzly bear vital rates, and thereby to help evaluate the effectiveness of past management and to identify future conservation issues. We concluded that, within the limits of uncertainty implied by the available data and our methods of data analysis, the size of the Yellowstone grizzly bear population changed little from 1975 to 1995. We found that grizzly bear mortality rates are about double in years when the whitebark pine crop fails than in mast years, and that the population probably declines when the crop fails and increases in mast years
"We calculate that [the mean population growth rate] = 1.00 from 1975 to 1983 (four mast and five nonmast years) and 1.02 from 1984 to 1995 (seven mast and five nonmast years). Overall, we find that [the mean population growth rate] = 1.01 +/- 0.04 (mean +/- 1 SE) from 1975 to 1995.
"Our models suggest that future management should concentrate on the threats to whitebark pine, such as those posed by white pine blister rust, global warming, and fire suppression. As is currently widely recognized by Yellowstone land managers, our model also suggests that future management must compensate for the increased grizzly bear mortality that is likely to be caused by an increasing number of humans in Yellowstone.