Modeling for Endangered-Species Recovery: Gray Wolves in the Western Great Lakes Region

Abstract

The Federal Endangered Species Act is intended to conserve endangered and threatened species and their habitats and to improve the species' status so that they no longer need protection under the Act. In the process of planning the recovery of threatened or endangered species, the U.S. Fish and Wildlife Service increasingly uses demographic models to predict population growth and risk of extinction, investigate the factors responsible for species endangerment, and examine the relative effectiveness of alternative management options for species recovery. Demographic models range from simple matrix models for estimating population change (Getz and Haight 1989) to complex, spatially explicit, individual-based models of population dynamics (Dunning et al. 1995). Such models require at a minimum an understanding of the age, stage, and social structure of the population and estimates of reproductive success and survivorship for different life stages. The purpose of this chapter is to describe an example of the construction of a demographic model with application to questions associated with the recovery and management of the endangered gray wolf (Canis lupus) population in the western Great Lakes region of the United States.