AREA-RESTRICTED SEARCH BY THE PLAINS POCKET GOPHER (GEOMYS-BURSARIUS)IN TALLGRASS PRAIRIE HABITAT

Because pocket gophers have the high energetic cost of excavating burr ows 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 hyp othesis I compared gopher foraging effort over a 10-month period betwe en areas in which overall plant densities were experimentally varied. Gophers expended approximately 50% of their foraging effort in areas w ith the highest plant density, even though these made up only 33% of t he available area in experimental plots. In large, gridded areas sampl ed for an entire season as well as in small areas in which gophers for aged for less than 1 week, gopher foraging effort was related to the d ensity of a single leguminous plant species, Psoralea argophylla. In s mall plots where this plant species was at high density, gophers creat ed more tunnel branches, thereby intensifying their search effort. Thu s, area-restricted search appears to increase the rate of encounter wi th the patchily distributed Psoralea plants.