Habitat of Pocket Gophers in Cochetopa Creek Drainage, Colorado

Abstract

Comparisons were made between some characteristics of soils and vegetation for sites supporting Thomomys talpoides and for adjacent sites not occupied by these pocket gophers in alpine, subalpine and shrub-grassland habitats in the Cochetopa Creek drainage, Colorado. Different species of bluegrasses (Poa spp.), sedges (Carex spp.), cinquefoils (Potentilla spp.), and bluebells (Mertensia spp.) occurred in the alpine, subalpine, and shrub-grasslands. There were 16 species of plants common to the alpine and subalpine, three species of plants oc- curred in both the subalpine and shrub-grasslands and two species occurred in both the shrub-grasslands and the alpine. Alpine skyrocket (Androsace septentrionalis puberulenta) occurred in all three habitats. Plant composition was very similar between sites occupied by pocket gophers and adjacent unoccupied sites. Those differences detected did not appear great enough to account for the presence or absence of pocket gophers. Soils in the alpine were shallower where gophers occurred than were soil depths on unoccupied sites, but in the subalpine and shrub-grasslands soils were deepest at sites occupied by pocket gophers. In general, soils were deep enough to support pocket gopher burrows at all sites sampled. There was a decrease in mean soil temperature with an increase in elevation. Soils inhabited by gophers in the shrub-grasslands varied from about 7% to 12% moisture and those in the subalpine and alpine varied from about 25% to 55%. The rock composition of soils occupied by pocket gophers and adjacent unoccupied soils was similar in the subalpine but in both the alpine and shrub-grasslands the unoccupied soils contained more rocks larger than one-half inch in diameter than did soils supporting pocket gophers. Some pocket gopher mounds were made up of 40% rocks (larger than one-fourth inch in diameter) in the shrub-grasslands, up to 31% in the alpine and as much as 16 % in the subalpine. Pocket gopher mounds contained fewer large rocks than did the topsoil at sites occupied by pocket gophers. It appears that pocket gophers could occupy more area in the alpine, subalpine, and shrub-grasslands than they now occupy.