Tracking the wildlife in Ankarana, a "true lost world" in northern Madagascar, where jagged, 1000-foot ridges wall off lush forests. The rulers of Ankarana: Nile crocodiles, sun lovers that nonetheless live in caves that honeycomb the ridges. The reason why they do intrigues French scientist Olivier Behra. Meanwhile, American biologist Luke Dollar is interested in the fossa, a "superpredator" he likens to "a mongoose on steroids." A fossa is seen here stalking Madagascar's signature animal, the lemur, primative primates that some people believe have human souls.