Area-restricted search by the plains pocket gopher (Geomys bursarius) in tallgrass prairie habitat

Because pocket gophers have the high energetic cost of excavating burrows and an inability to detect distant food items through the soil, I hypothesized that individuals within established burrow systems would use area-restricted search as a foraging strategy. To examine this hypothesis I compared gopher foraging effort over a 10-month period between areas in which overall plant densities were experimentally varied. Gophers expended approximately 50% of their foraging effort in areas with the highest plant density, even though these made up only 33% of the available area in experimental plots. In large, gridded areas sampled for an entire season as well as in small areas in which gophers foraged for less than 1 week, gopher foraging effort was related to the density of a single leguminous plant species, Psoralea argophylla. In small plots where this plant species was at high density, gophers created more tunnel branches, thereby intensifying their search effort. Thus, area-restricted search appears to increase the rate of encounter with the patchily distributed Psoralea plants.