Northern Prairie Wildlife Research Center
We studied swift fox (Vulpes velox) on the Piñon Canyon Maneuver Site (PCMS) in southeastern Colorado from March 1986 to September 1987. Mean minimum convex polygon home range size of adult swift fox was 29.0 km2 (n = 5, range = 12.8 to 34.3 km2). Although home ranges of family groups showed appreciable overlap with adjacent groups, 50% harmonic mean activity areas were almost entirely exclusive. Swift fox diet consisted primarily of small mammals (monthly mean % volume = 64%), arthropods ( = 19%), and small birds ( = 8%). Mean litter size (n = 5) was 3.4 (range = 2 to 5) and not all females produced litters. Predation by coyotes (Canis latrans) was the primary cause of fox mortality over the course of the study. We conclude that where coyotes are abundant, predation by coyotes is a significant source of mortality for swift fox and that den availability might be an important aspect of swift fox management.