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Using radiotelemetry, we studied home range and movements of 32 adult female and 16 adult male Mohave ground squirrels (Spermophilus mohavensis) in the western Mojave Desert of California during 1990 and from 1994 to 1997. In 3 of the 5 years of study (1990, 1994, and 1996), early winter precipitation (October-January) was <30 mm, and no reproduction occurred at the study site. Postmating home ranges of females varied considerably among years, with annual medians for minimum convex polygons ranging from 0.29 to 1.90 ha. Females used the largest home ranges both during years of ample rainfall and reproduction (1995 and 1997) and during the year of most extreme drought and no reproduction (1990). We hypothesize that variation in home-range size among drought years may result from varying levels of food availability. In 1997, we also studied movements of adults during the mating season, from mid-February to mid-March. During this period, adult males made extensive movements, resulting in median minimum convex polygons much larger (6.73 ha) than those of females (0.74 ha). Such movements would have made it possible for males to locate adult females soon after their emergence from hibernation. Patterns of variation in home-range size and movements observed during this study may reflect adaptive responses of this small herbivore to a highly variable, and environment.