Dispersal in a Population of Desert Rodents

Dispersal of two species of kangroo rats and two species of pocket mice in the Mojave Desert was examined by live-trapping intensively an 8-ha ( 20-acre) area, and by setting rows of live-traps at 152-m (500 ft) intervals out to 914 m (3000 ft) from the area. Dispersal distances of Perognathus formosus were arranged in a frequency distribution. Dispersal appears to be nonrandom. There were too many moves to great distances and too few to intermediate distances for dispersal to be considered random. The results support the hypothesis that some members of the population have an instinct to disperse, and that their moves are long distance ones. Both young and old animals made dispersal movements, some more than once. We estimate 25 to 30% of the P. formosus made dispersal movements during the period of 1 year. Kangaroo rats wander during the non-breeding season, but our sampling was not adequate to evaluate dispersal of these rodents.