Ecological and morphological relationships of subspecies of Peromyscus maniculatus near St. Mary, Montana

Glazier, Ronald

For a period of five months between June 22 to September 7, 1967 and from June 27 to September 5, 1968, a live trapping study was undertaken near the St. Mary region, Glacier National Park, Montana, to determine the ecological distribution and analyze morphological variation of two subspecies of Peromyscus maniculatus, P_. m. artemesiae and P. m. osgoodi. Morphological measurements were taken on adult mice only. Mean lengths of tail, ear, hind foot and skull are significantly greater in P. m, artemesiae than P. m. osgoodi. Body length, nasal length and mastoid breadth are not reliable measurements for distinguishing between individuals of populations of the two subspecies, Nine individuals of intermediate measurements are classified as suspected hybrids. Three general habitats are found in the study area, grassland, aspen groveland and coniferous forest. Allopatric P.m. osgoodi populations are found in the grasslands and meadows and disturbed areas of the aspen groveland. Allopatric P_. m. artemesiae populations are found in the coniferous forest and the meadows in that forest. The sympatric area corresponds roughly to the narrow groveland-coniferous forest ecotone. Regardless of general habitat the mice are found in those areas where ground vegetation is light but places for concealment are abundant. Although contact was found between the subspecies in three areas, contact in general appears to be limited by the dense vegetation along the sympatric contact line. Hybrids may occur, but they are limited in number. Isolating mechanisms other than habitat selection may be involved.