The desert tortoise is a threatened species throughout much of its range which includes both the Sonoran and Mojave deserts. Recently the desert tortoise was split into 2 separate species.The Agassiz's desert tortoise (Gopherus agassizi) lives in the Mojave deserts of California, Nevada, Utah, and Arizona west of the Colorado river. The Morofka's desert tortoise (Gopherus Morafkai) resides in the Sonoran deserts of Arizona east of the Colorado river and Mexico. The 2 species can interbreed and many of the captive tortoises in the Phoenix area are hybrids, which can only be determined by genetic testing.
Wild desert tortoise populations are threatened by development and destruction of natural habitat. In the meantime, captive tortoises have the opposite problem and have become over-populated. Large numbers of tortoises now sit homeless in sanctuaries throughout the southwest US. Wildlife officials are unable to return these captive to the wild because many are hybrids and there is a high risk of exposing wild tortoises to any diseases carried by these pet tortoises.