Swift fox survival and production in southeastern Wyoming

We estimated annual survival rates of swift foxes (Vulpes velox) and documented number of young per pair in a transition zone between shortgrass prairie and sagebrush steppe plant communities in southeastern Wyoming during 1996-2000. Annual adult survival ranged from 40% to 69%, with predation by coyotes (Canis latrans) the primary cause of deaths. Two foxes died of canine distemper virus. Annual survival rates did not differ among years (P>0.12). Nineteen of 24 (79%) swift fox pairs were observed with young over 3 years. Mean minimum litter size was 4.6 based on these 19 litters and 6 others not associated with our radiocollared foxes. Adult survival was similar and litter size slightly larger than observed elsewhere in the species range, suggesting that viable swift fox populations can be supported by sagebrush steppe and shortgrass prairie transition habitat.