Home Range Dynamics in a Population of Heteromyid Rodents

Seasonal, sexual, and temporal aspects of home range for pocket mice (Perognathus formosus and P. longimembris) and kangaroo rats (Dipodomys merriami and D. microps) were analyzed from records accumulated over 7 years of monthly censuses of the rodents in three 9-hectare enclosures and one similar area not enclosed in the Mojave Desert. The density function was used as a standard expression (in terms of sigma) to compare home ranges of different individuals, groups or species, or over time. Detailed analysis of 340 P. formosus in one enclosure showed that 16 shifted locations of their home range during the course of this study, and 99 were detected to make one or more long-distance excursions beyond their home range. Compilation of all data gives an average representation of home range for this species in this environment to be a circle of radius 31 meters, which will encompass 86 per cent of the animals' activity. This radius is the 2 sigma value computed from the data. Size of home range differs between sexes and among years, with significant year by sex interaction. There is an inverse relationship between population density and size of home range. Home range size is not related to body size in the four species studied, which presumably occupy the same trophic level of the system. Shifts in home range and excursions outside the established home range occurred most frequently in males and most frequently in the reproductive season.