2. Historical Biogeography of the Wolverine
in the United States

We compiled current and historical records of wolverine (Gulo gulo) occurrence in the contiguous United States from published literature, museums, state wildlife agencies, federal resource management agencies and natural heritage databases. Records obtained were of varying degrees of reliability; they included many museum specimens, photos and first- hand accounts of wolverines being trapped (verified records), but were dominated numerically by visual observations of wolverines or their tracks (unverified records). Resulting biogeographic analyses, including assessments of the current and historical distribution of wolverines in the United States, and correlations between elevation and land-cover types varied substantially in accordance with the reliability of occurrence records included in the analyses. Specifically, the geographic distribution of wolverines based only on verified records is much more disjunct and isolated within high-elevation, boreal habitats than is depicted in published range maps. The distribution of verified records also suggests that wolverines have been absent for many years from California, Colorado and the Great Lakes states. We compare inferences resulting from various data sets and discuss the challenges and conservation implications of determining the current and historical ranges of rare and secretive species that have not been surveyed with reliable methods.