Daniels, J.M. 1980. Field study on Microtus chrotorrhinus. Final report submitted to the Minnesota Department of Natural Resources. 20 pp.
The study of Microtus chrotorrhinus, the rock vole or yellow-nosed vole, was designed to meet two objectives. The first objective was to test the hypothesis that water, in the form of humidity and available free water, is a limiting factor in habitat selection by M. chrotorrhinus. The second objective of the study was to locate additional populations of the species in northeastern Minnesota and supply this information to the Minnesota Natural Heritage Program. Protection of these colonies may be necessary due to the rarity of the species in Minnesota and the limited and unique habitat in which it exists.
To test the hypothesis that water is a limiting factor in habitat selection by M. chrotorrhinus, I proposed to compare the water requirements of M. chrotorrhinus with two closely related species: Clethrionomys gapperi and Microtus pennsylvanicus. Field work was to include trapping to determine species distribution and various population parameters and measurement of several microclimate parameters at the two sites throughout the summer.
Following the discovery of three new colonies of M. chrotorrhinus, it may be suggested that this species is more widespread in northern Minnesota than originally believed. The populations of these colonies, however, do not appear very large and it may be further suggested that although this species is widespread, it is not abundant in the state. Habitat preference of M. chrotorrhinus in Minnesota appears to follow the general pattern reported throughout its range. In the sites investigated, relatively high moisture levels, cool temperatures and adequate herbaceous cover appear to be most important. Though a wide diversity of forbs were common to the Minnesota sites, evidence of nibbling was found principally on blueberry and bunchberry plants. Boulders were abundant at all new sites but their significance is unclear.