Before Lewis and Clark explored the Louisiana Territory in 1804, little was known about the land or animals of that vast region, but President Jefferson directed the expedition to collect specimens and record observations, and the explorers' reports stimulated interest in the new land. More than 175 years later, continued observation of nature has brought greater awareness of the complex relationships between plants and animals in this unique swamp habitat, where inhabitants have developed physical and behavioral characteristics that enable them to live in harmony. Reptiles long inspired fear among settlers and rural residents, and swamps were once avoided on foot, but scientific study has shown their value to the swamp habitat and the wider environment. Cottonmouths, the most common poisonous snakes in the swamp, feed on frogs and fish and are usually unobtrusive unless molested, while diamondback watersnakes are harmless snakes that also feed on frogs and fish and can be distinguished by head shape and skin patterns. Common snapping turtles, though vicious when handled, act as swamp scavengers by feeding on dead animals, and the American alligator, once considered endangered, is increasing in number, occurs in eastern Arkansas, and has been spotted in this swamp. Trees and shrubs provide food and shelter for other swamp residents, with more than nine species visible from the boardwalk, including button bush, bald cypress, swamp cottonwood, swamp chestnut oak, and water tupelo. Birds are the swamp's most conspicuous residents, including pileated woodpeckers, which feed on larvae and grubs from dead and living trees and are known for their drumming and repeated calls; wood ducks, which nest in tree cavities and feed on aquatic plants and insects; and prothonotary warblers, common in wooded swamps near water, which nest in tree cavities over low water and sing a loud, clear song.