Michael K. Phillips

WOLF–BISON INTERACTIONS IN YELLOWSTONE NATIONAL PARK

Abstract We studied interactions of reintroduced wolves (Canis lupus) with bison (Bison bison) in Yellowstone National Park. Only 2 of 41 wolves in this study had been exposed to bison before their translocation. Wolves were more successful killing elk (Cervus elaphus) than bison, and elk were more abundant than bison, so elk were the primary prey of wolves. Except for a lone emaciated bison calf killed by 8 1-year-old wolves 21 days after their release, the 1st documented kill occurred 25 months after wolves were released. Fourteen bison kills were documented from April 1995 through March 1999. All kills were made in late winter when bison were vulnerable because of poor condition or of bison that were injured or young. Wolves learned to kill bison and killed more bison where elk were absent or scarce. We predict that wolves that have learned to kill bison will kill them more regularly, at least in spring. The results of this study indicate how adaptable wolves are at killing prey species new to them.

Defining Recovery Goals and Strategies for Endangered Species: The Wolf as a Case Study

Abstract We used a spatially explicit population model of wolves (Canis lupus) to propose a framework for defining rangewide recovery priorities and finer-scale strategies for regional reintroductions. The model predicts that Yellowstone and central Idaho, where wolves have recently been successfully reintroduced, hold the most secure core areas for wolves in the western United States, implying that future reintroductions will face greater challenges. However, these currently occupied sites, along with dispersal or reintroduction to several unoccupied but suitable core areas, could facilitate recovery of wolves to 49% of the area in the western United States that holds sufficient prey to support wolves. That percentage of the range with recovery potential could drop to 23% over the next few decades owing to landscape change, or increase to 66% owing to habitat restoration efforts such as the removal of some roads on public lands. Comprehensive habitat and viability assessments such as those presented here, by more rigorously defining the Endangered Species Acts concept of “significant portion of range,” can clarify debate over goals for recovery of large carnivores that may conflict with human land uses.

Normativity and the Meaning of Endangered: Response to Waples et al. 2007

There has been increased interest recently in better understanding the meaning of endangered species as defined in the 1973 U.S. Endangered Species Act (ESA). Waples et al. (2007) provide an account that is, in part, a reaction to a position presented by us in Vucetich et al. (2006). Here, we extend this discussion with comments focused on Waples et al. (2007). In the ESA an “endangered species” is defined as one “in danger of extinction throughout all or a significant portion of its range” (SPOIR). Although we (Vucetich et al. 2006) claim that the term SPOIR is fundamentally normative, Waples et al. develop a specific definition for the critical phrase significant portion of its range (SPOIR) and suggest that the “apparently normative language” can be a “largely scientific exercise.” If their definition is used to replace the SPOIR wording in the ESA’s definition of an endangered species, then an endangered species would be defined as one “in danger of extinction throughout all [of its range or in] geographic area(s) that contains population unit(s) that, if lost, would cause the entire species to be in danger of extinction or likely to become so in the foreseeable future.” Waples et al. appear to be motivated, at least in part, by what may be a common misunderstanding among scientists of the nature of normativity. First, however, we identify one independent concern with the solution presented by Waples et al. At the very least, the awkward and obfuscating grammar of the definition of Waples et al. is problematic. Accepting the interpretation by Waples et al. of SPOIR, however, might allow endangered species in the ESA to be redefined as a species that is either (1) “likely to become in danger of extinction in the foreseeable future” or (2) “in danger of extinction.”