Owens Valley Vole Research

Lead CDFW biologist: Alisa Ellsworth, Steve Parmenter, Brett Parmenter

The Owens Valley vole (Microtus californicus vallicola) is a little known subspecies of California vole located in the Owens Valley of California. It is a California State Species of Concern, but very little is known about the status of the population and threats to its existence. Pleistocene climate change and mountain barriers are thought to have geographically isolated this subspecies from the other California voles for more than 14,000 years. Multiple factors such as natural aridity, land cultivation, construction of highways and canals, and local urbanization have fragmented the subspecies into an unknown number of subpopulations (USFWS 1998).

Fragmentation and small population size are risk factors for population bottleneck, genetic drift, and potential loss of fitness (Nuewald 2002, H' glund 2009). A study was initiated in the summer of 2011 to investigate potential environmental impact by humans on the Owens Valley vole through genetic analysis. Genetic variation and population structure of the Owens Valley vole were used to assess divergence among subpopulations, and to test for potential recent losses of genetic diversity due to anthropogenic impacts. Understanding past disturbances to voles through genetic characterization will allow wildlife managers to define appropriate conservation management units, specific treatment areas for the protection of the species. Evidence of recent (human-caused) erosion of genetic diversity will forewarn managers of jeopardized population viability and the need to establish protected areas, migration corridors, and/or genetic monitoring.

Three trapping sites were selected that represented the northernmost and southernmost known portions of the Owens Valley voles range as well as a site in the middle. These sites were Fish Slough Ecological Reserve, Black Rock on the Owens River and Cartago Springs Wildlife Area. All voles were trapped using standard techniques using Sherman live traps. The trapped voles were weighed and measured and genetic samples were taken before being released. Genetic samples were later analyzed at the Museum of Vertebrate Zoology at U.C. Berkeley. Allelic richness is roughly equal across the range of the Owens Valley vole.

Analysis of the genetic material from the three sites yielded some interesting insights into the Owens Valley Vole. Two species were detected co-existing at Fish Slough Ecological Reserve, the Owens Valley vole and Montane vole (Microtus montanus). Genetic richness is roughly equal across the range of the Owens Valley vole. There appear to be healthy breeding populations throughout the range of the vole.