 The Key Largo Woodrat, Key Largo Cotton Mouse, Schaus Swallowtail butterfly, Florida semaphore cactus are listed as endangered, and the Stock Island Tree Snail and Eastern Indigo Snake are listed as threatened.All six species retain a precarious foothold in North Key Largo.Due to the once almost unrestricted commercial and residential development of the Florida Keys, the size and number of fragmented tropical hardwood hammock habitat have been reduced.