Spatial relationships between swift foxes and coyotes in northwestern Texas

Abstract

Interspecific competition among canids can result in mortalities and spatial displacement of smaller canids by larger canids. To investigate mortalities and spatial relationships of swift foxes (Vulpes velox) and coyotes (Canis latrans), we captured and radio-tracked both species at Rita Blanca National Grasslands in northwestern Texas. At least 89% of swift fox mortalities were caused by coyotes, resulting in a relatively low annual survival of 0.47 for swift foxes. Annual home ranges of swift foxes occurred near the periphery and outside coyote home ranges, and did not overlap or only slightly overlapped coyote core areas. Thirty-three of 36 known swift fox dens occurred outside coyote core areas. When swift foxes established dens within coyote core areas (n = 3), they were killed by coyotes shortly thereafter. Our data indicated that spatial displacement of swift foxes was not due to behavioral avoidance of coyotes but rather to increased killing of swift foxes within coyote core areas. Most mortalities caused by coyotes occurred in the immediate vicinity of swift fox dens, suggesting that coyotes made an active effort to kill swift foxes.