干旱区生态环境知识资源中心

Native and nonnative red foxes (Vulpes vulpes) reportedly occur in North America, although the origin and taxonomy of many populations often are unknown and disputed. To help elucidate the origin and taxonomy of red fox populations in North America, we conducted a literature review that focused on the historical distribution of native red foxes, known populations of nonnative red foxes, range expansions during the 1900s, taxonomic and ecological differences between native and nonnative red foxes, and impacts of nonnative red foxes on native species. Our review indicated that native red foxes are a boreal species that historically occurred in the northern regions of North America and in the southern refugia of montane habitats at higher elevations throughout the western United States. Nonnative red foxes, from European origin, were introduced throughout the eastern United States and in lowland areas in the Pacific coast states. From a source population in the eastern United States, red foxes expanded westward throughout the central United States and Canada during the 1900s, indicating that these red foxes were nonnative. Nonnative red foxes thrive in human-altered habitats such as urban and agricultural areas and have invaded diverse ecosystems ranging from desert to arctic tundra. Nonnative red foxes have negative impacts in many ecosystems where they now occur because they are generalist predators that attain relatively high densities. Nonnative red foxes likely replaced native red foxes throughout all northern boreal regions and may threaten remaining native populations at higher elevations in the western United States. The taxonomy of red foxes in North America needs to be re-evaluated. Although native and nonnative red foxes in North America are considered conspecifics, there are substantial differences in coloration, morphology, behavior, and habitat requirements between these 2 types.