Sex differences in reproductive investment influence space use patterns of many animals. In polygynous mammals, male space use reflects distribution of females and female space use reflects relative distribution of food. We used radiotelemetry to examine seasonal patterns of home-range size, overlap, and distance traveled by male and female Chiricahua fox squirrels (Sciurus nayaritensis chiricahuae) from 2002 to 2003. Male and female home-range and core-area size varied little between nonmating and mating seasons. Female core areas had a greater percentage overlap by males than by females during mating and nonmating seasons. Males traveled farther in the mating season and females showed little variation between seasons. Extreme spatial and temporal fluctuations of food experienced by Chiricahua fox squirrels may result in space use patterns that differ from those of tree squirrels living in forests with a greater abundance of food.