Black bears (Ursus americanus) as a novel potential predator of Agassiz’s desert tortoises (Gopherus agassizii) at a California wind energy facility

Abstract

Black bears (Ursus americanus) and Agassiz’s desert tortoises (Gopherus agassizii) rarely interact due to substantial differences in their preferred habitats. In this paper we report a mother and cub black bear investigating an occupied tortoise burrow in a wind energy generation facility in the San Bernardino Mountains northwest of Palm Springs, California. While predation was not observed, bears are known to eat various turtle species around the world on an opportunistic basis. Given the proclivity of black bears to adopt specialized dietary opportunities on a learned, individual basis, the potential exists for predation on desert tortoises. Since black bears were not native to southern California prior to 1933, tortoises would have little experience avoiding black bear predation if it occurred. We review the literature on bears eating turtles worldwide and discuss an example of another novel mammalian carnivore negatively affecting a population of desert tortoises.