The Okefenokee Swamp includes low, sandy ridges, wet, grassy savannas, small islands (called hummocks) surrounded by marshes, and extensive “prairies,” or dark water areas covered by undergrowth and trees. Vegetation is dense in the swamp and includes giant tupelo and bald cypress trees festooned with Spanish moss, brush, and vines; where sandy soil is above the water, pine trees predominate. Meandering channels of open water form an intricate maze. Exotic flowers, among them floating hearts, lilies, and rare orchids, abound. The swamp is populated with diverse and abundant wildlife, with about 175 species of birds and at least 40 species of mammals, which include raccoons, black bear, white-tailed deer, bobcats, fox, and otter. Alligators are also present.