EFFECTS OF SPECIES, SEX, AGE, AND HABITAT ON GEOMETRY OF POCKET GOPHER FORAGING TUNNELS

Abstract

Home-range size and shape are influenced by cost–benefit relationships associated with acquiring resources. Subterranean animals may be particularly affected by food availability and soil conditions because of the close coupling of their activity to soil and the high energetic expense of digging. We examined foraging tunnel length, area, and geometry (e.g., number of branches and turning angles) of 3 species of pocket gophers (Geomys attwateri, Geomys bursarius, and Thomomys bottae) in their natural habitats, which differed in food abundance and soil characteristics. Burrow features (except length and area) were similar among species, sexes, ages, and habitats. However, burrows of adults were longer and occupied larger areas than those of juveniles, and burrow system length and area decreased with increasing vegetation biomass and with increasing soil clay content of soil (i.e., increasing expense of digging). Our findings reveal common patterns of burrow geometry, which suggest that there may be an underlying strategy defining geometric features of burrows within this family of subterranean rodents.