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International Journal of Ecology
Volume 2010 (2010), Article ID 924197, 5 pages
http://dx.doi.org/10.1155/2010/924197
Research Article

Trend of the Yellowstone Grizzly Bear Population

12528 W. Klamath Avenue, Kennewick, WA 99336, USA
2National Marine Fisheries Service, National Marine Mammal Laboratory, 7600 Sand Point Way NE, Bldg. 4, Seattle, WA 98115, USA

Received 4 March 2010; Accepted 8 April 2010

Academic Editor: Mats Olsson

Copyright © 2010 L. L. Eberhardt and J. M. Breiwick. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Yellowstone's grizzlies (Ursus arctos) have been studied for more than 40 years. Radiotelemetry has been used to obtain estimates of the rate of increase of the population, with results reported by Schwartz et al. (2006). Counts of females with cubs-of-the-year “unduplicated” also provide an index of abundance and are the primary subject of this report. An exponential model was fitted to such counts, using nonlinear leastsquares. Estimates of the rate of increase, r, were about 0.053. 95% confidence intervals, were obtained by several different methods, and all had lower limits substantially above zero, indicating that the population has been increasing steadily, in contrast to the results of Schwartz et al. (2006), which could not exclude a decreasing population. The grizzly data have been repeatedly mis-used in current literature for reasons explained here.