Hualapai Mexican Vole
Hualapai Mexican Vole
Microtus mexicanus hualpaiensis
|Listed||October 1, 1987|
|Family||Muridae (Mice and Rats)|
|Description||Cinnamon-brown, mouse-sized with a short tail and long fur rodent.|
|Habitat||Wet, woodland meadows.|
|Threats||Low numbers, livestock grazing, erosion, recreation.|
The Microtus mexicanus hualpaiensis (Hualapai Mexican vole) is a cinnamon-brown, mouse-sized rodent with a short tail and long fur that nearly covers its round ears. It is distinguished from its eastern relative, M. m. mogollonensis, by its paler back color, shorter body, shorter and broader skull, and longer tail and hind foot. It is distinguished from M. m. navaho, found to the northeast, by its generally larger size, a longer and broader skull, and a longer tail, body, and hind foot.
The Hualapai vole's life history and reproductive biology have not been studied. Voles are active day and night and are good swimmers; they eat grass, bark, seeds, and roots. Their voice is a high-pitched squeak.
This species inhabits meadows of grasses, sedges, and forbs within ponderosa pine forests on steep mountain slopes. It is currently restricted to moist areas around springs and seeps but may be capable of occupying drier areas where ground cover is suitable. Habitat elevation is between 5,397 and 8,400 ft (1,645 and 2,560 m).
This vole was first described from specimens collected near the summit of Hualapai Peak in northwestern Arizona in 1923. Only 15 confirmed Hualapai voles have ever been captured, all from the Hualapai Mountains; the last was collected in 1984. Besides these confirmed individuals, other suspected Hualapais have been found elsewhere—in the Music Mountains 50 mi (80 km) north and Prospect Valley 90 mi (145 km) northeast of Hualapai Peak. These disjunct sites may represent a relict vole population that survived when the Pleistocene glaciers retreated. The rare Hualapai vole has one of the most restricted ranges of any mammal in North America. It currently occupies isolated patches of meadow around widely separated seeps on Hualapai Peak. Most sites where evidence of the vole have been found occur on lands managed by the Bureau of Land Management (BLM) as part of a regional grazing allotment. Other parcels of potential habitat are owned by Mohave County, the Santa Fe Pacific Railroad Company, and private owners. During a 1984 survey biologists located the vole or its sign at three sites, totaling less than 1 acre (0.4 hectare) in area. In 1991, the Arizona Game and Fish Department (AGFD) conducted surveys (funded by the Fish and Wildlife Service under Section 6 of the Endangered Species Act) to locate voles in Mohave and Coconino counties, Arizona. The surveys focused on the Hualapai and Music Mountains and the Hualapai Indian Reservation. Twenty-eight voles were found during the surveys—20 in the Hualapai Mountains, four in the Music Mountains, and four on the Hualapai Indian Reservation. The 1992 AGFD spring surveys found five voles in two new locations in the Hualapai Mountains, and summer surveys found 17 individuals located in two old and two new sites in the Hualapai Mountains.
Erosion, caused by poor land management practices and periods of drought, have degraded much of the vole's habitat. The shallow soils of the region are maintained by the grassy ground cover. Grazing cattle have denuded large tracts of grasses and forbs, leading to loss of topsoil. Remaining habitat springs attract livestock, but also campers and off-road vehicle enthusiasts, who have damaged plants and contributed to erosion. Mohave County land is nominally protected as a county park, but cattle from adjacent pastures graze there as well. The county is also considering constructing a lake in the area, which would increase the number of recreational visitors. Of the three known habitats not currently showing signs of vole activity, one has been degraded by sediments washed into the habitat by flood events, and another receives heavy recreational use that has degraded vole habitats there. All habitats were diminished by drought conditions in the past decade.
Conservation and Recovery
Because most of the Hualapai vole's habitat is on BLM lands, that agency's cooperation will be critical to the survival of the species. The BLM is currently reexamining its land use policies and may restrict future cattle-grazing allotments and water allocations. The 1991 Recovery Plan for the species calls for the protection of existing populations through habitat protection and identification. Until the serious declines in both habitat and population levels are controlled, long-term recovery is not achievable.
Arizona Game and Fish Commission. 1982. Threatened Native Wildlife in Arizona. Arizona Game and Fish Department Publication, Tucson.
Goldman, E. A. 1938. "Three New Races of Microtus mexicanus." Journal of Mammalogy 19:493.
Hoffmeister, D. F. 1986. Mammals of Arizona. The University of Arizona Press, Tucson.
U.S. Fish and Wildlife Service. 1991. "Recovery Plan for the Hualapai Mexican Vole." U.S. Fish and Wildlife Service, Albuquerque.