Next airing Fri Sep 2, 1 p.m. ET

Urban Jungle

We might think our cities of concrete and steel are immune to the dangers of nature, but buried beneath is a world inhabited by mammals, arachnids and reptiles equipped with an arsenal of predatory and defensive skills. In South America, vampire bats invade human settlements; in Cairo the Egyptian cobra lurks in the back alleys; and the rattlesnake stalks Southern California.