The island fox shares the Urocyon genus with the mainland gray fox, the species from which it is descended. Its small size is a result of insular dwarfism, a form of allopatric speciation. Because the island fox is geographically isolated, it has no immunity to parasites and diseases brought in from the mainland and is especially vulnerable to those that the domestic dog may carry. In addition, predation by the golden eagle and human activities devastated fox numbers on several of the Channel Islands in the 1990s. Four island fox subspecies were federally protected as an endangered species in 2004, and efforts to rebuild fox populations and restore the ecosystems of the Channel Islands are being undertaken. Radio collars are being attached to foxes in an effort to track and locate the young foxes. To date these efforts have been largely successful.