Livestock Grazing Influences Habitat and Local Extirpations of the Arizona Montane Vole in New Mexico

Abstract The montane vole Microtus montanus is a locally abundant rodent that is associated with grassy areas that provide cover for its runways. The Arizona montane vole Microtus montanus arizonensis is a subspecies restricted to the White Mountains region of east-central Arizona and adjacent areas of New Mexico, where it is listed as endangered. The goal of this study was to determine the distribution of the vole in New Mexico and identify habitat characteristics. We surveyed for the vole in New Mexico during 2004 and 2020. In addition, we collected landscape scale habitat and microhabitat data during surveys for voles in New Mexico, as well as during a separate small mammal study conducted in Arizona during 2008 and 2009. We documented voles at 11 new sites in New Mexico based on field surveys and examination of museum specimens. In 2020 we only detected voles at one site where it was historically documented, representing an 83% decline. There was moderate evidence that stream reaches where montane voles were captured had higher vertical cover and suggestive evidence that these reaches had more cover of shrubs than reaches where they were not captured. Microhabitat at capture locations had saturated soil, low canopy cover, high vertical cover, and ground cover dominated by sedges. Vertical cover was higher and Arizona montane voles were more likely to be captured at sites where livestock grazing was not permitted. We conclude that livestock grazing management has resulted in the near extirpation of this small mammal from New Mexico.