Matching the color of excavated soil: Cryptic coloration in the plains pocket gopher (Geomys bursarius)

The plains pocket gopher (Geomys bursarius) is a fossorial rodent noted for having a wide range of pelage colors that tend to match the color of soil in which it lives. This phenomenon is considered adaptive as concealing coloration. If being well camouflaged is advantageous, then natural selection should favor a pelage color that specifically matches the color of soil that surrounds pocket gophers when they are most often exposed to the surface. We tested the hypothesis that dorsal coloration of G. bursarius matches color of moist, freshly excavated soil from its burrow more closely than color of drier soils that surround newly formed mounds. Our study examined 5 subspecies that live in soils having different colors (black, dark brown, reddish brown, yellowish brown, and white). The degree of cryptic coloration was quantified using methods that do not reflect biases of color perception by humans. At all locations, color of the pocket gophers' heads was closer to color of dark moist soil than to the color of pale dry soil. The same was true for their backs, except for a brown individual from the black soils of Illinois.