Predation on San Joaquin Kit Foxes by Larger Canids

A better understanding of the relationships between endangered San Joaquin kit foxes (Vulpes macrotis mutica) and sympatric larger canids that prey on them is important for conservation efforts toward kit foxes. We used radiotelemetry to monitor the survival and cause of death of 41 San Joaquin kit foxes and 24 coyotes (Canis latrans) on the Carrizo Plain Natural Area, California, during the 1989-1991 drought. The estimated minimum-annual-survival rate for all coyotes was 0.88. Estimated annual-survival rates for juvenile foxes (0.21-0.41) were somewhat less than those for adult foxes (0.58-0.61). Survival rates for foxes were similar across years and sexes. Larger canids accounted for 78% of 23 verified deaths of kit foxes: 15 killed by coyotes; 2 by non-native red foxes (Vulpes vulpes); 1 by a domestic dog. High predation by larger canids, coupled with poor reproduction in kit foxes due to reduced prey availability during the drought, contributed to a significant decrease in density of kit foxes (from 0.24 to 0.12 foxes/ km2) during the study. Although coyotes can have a significant impact on populations of kit foxes, larger non-native red foxes may pose a greater threat in some areas.