An American alligator is seen among mongrove in the Everglades National Park in Florida, the United States, Oct. 27, 2013. Everglades National Park is the largest designated sub-tropical wilderness reserve on the North American continent. At the southern tip of Florida, the park has been called 'a river of grass flowing imperceptibly from the hinterland into the sea'. The exceptional variety of its water habitats has made it a sanctuary for a large number of threatened species. (Xinhua/Zhang Jun)