Movement of Rocks by Northern Pocket Gophers

Abstract
The relationship between composition of sizes of rocks in soils and digging behavior of Thomomys talpoides was studied in southwestern Colorado. Comparisons were made of the size-classes of rock in 1) the topsoil, 2) the soil mounds pushed to the surface in summer by pocket gophers, and 3) soil casts formed in winter by pocket gophers. Pocket gophers tended to avoid rocks larger than 2.5 cm diameter. They moved relatively fewer rocks to the surface when the soil was dry, and when the soil contained only a few large rocks. Rocks that were from 0.6 cm to 2.5 cm diameter were more abundant in mounds and casts than they were in the topsoil.