An investigation into the effect of individual personality on re-introduction success, examples from three North American fox species: swift fox, California Channel Island fox and San Joaquin kit fox

Summary

Three imperiled North American canids, the swift fox (Vulpes velox, Threatened in Canada), the Endangered San Joaquin kit fox (Vulpes macrotis mutica), and the Critically Endangered Catalina Channel Island fox (Urocyon littoralis catalinae), were the subjects of a multi-project study testing whether individual boldness predicts reintroduction success and should inform release strategy. Researchers calculated boldness scores using novel-object tests for 34 captive-bred swift foxes released onto Montana's Blackfeet Indian Reservation and for 11 captive Catalina Channel Island foxes released in a predator-free environment, and used handling and novel-object tests to score free-living San Joaquin kit foxes in both urban and rural habitats of California's San Joaquin Valley as potential future reintroduction sources. Radio-collared swift foxes with higher boldness scores in a habitat with predators showed significantly higher mortality and moved farther from the release site, while bolder Catalina Island foxes, released into a predator-free setting, instead trended toward higher reproductive output; among free-living kit foxes, urban individuals were consistently bolder than rural ones, and within the rural population bolder animals had both higher mortality and, among survivors, larger litters and earlier first reproduction. Difficulties included incomplete monitoring data where stakeholders restricted trapping, adapting personality tests designed for captive animals to free-living foxes, limited staff time, and small sample sizes constraining statistical power. The project rates itself successful, crediting broad institutional and financial partnerships, and concludes that matching an individual's boldness to a release site's predator risk could improve future reintroduction outcomes.