Appraising status of the Yellowstone grizzly bear population by counting females with cubs-of-the-year

Abstract

The grizzly bear (Ursus arctos horribilis) in the lower United States was declared threatened in 1975 under the Endangered Species Act of 1973 (16 U.S.C. 1531-1544). According to that Act, the U.S. Fish and Wildlife Service had to prepare a plan to recover populations to levels where the species could be conserved and delisted from its threatened status. The Recovery Plan (U.S. Fish and Wildlife Service 1993) uses counts of distinct females with cubs-of-the-year as a recovery parameter in several grizzly bear ecosystems. The total number of these females is assumed to be the minimum number with cubs born in the current year. To our knowledge, this technique, its methodology, and value as a population indicator have never been adequately explained or discussed. Thus, we describe the methodology and assess its potential for continued use in the Yellowstone ecosystem.