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.