Patterns of Prairie Soil Preference and Occupancy for the Threatened Mazama Pocket Gopher in Washington

Abstract

Mazama pocket gophers Thomomys mazama act as ecosystem engineers and are keystone species on the remnant glacial prairies of the southern Puget Sound lowlands. Three subspecies of Mazama pocket gophers are regionally endemic to Thurston County, Washington, and were federally listed as threatened in 2014. We examined patterns of occupancy and habitat, and differences among subspecies for soil type preference. In total, 1,241 Mazama pocket gopher screening surveys, comprising approximately 4,654 hectares, resulted in 165 occupancy parcels. Pocket gophers were detected more often on parcels with more preferred soils than on less preferred soils, though there were differences in occupancy rates among subspecies. Soil type and availability can act as surrogates of gopher habitat availability. Such quantification of habitat availability and potential loss is important given the absence of population estimates. Therefore, the conservation of undeveloped lands with soils identified a priori as preferred is necessary for both the recovery and continued persistence of Mazama pocket gophers.