The large nocturnal aquatic salamander native to the eastern United States is the hellbender, Cryptobranchus alleganiensis.
Hellbenders are the largest salamanders in North America and live in cool, clean, fast-flowing streams. Their flattened bodies, wrinkled skin folds, and broad tails help them cling to the streambed beneath rocks. Those folds greatly increase surface area for cutaneous respiration, allowing the salamander to absorb much of its oxygen through the skin.
Hellbenders are generally most active at night, with activity often peaking around two hours after dark. They hunt crayfish, fish, worms, and other aquatic prey by probing the stream bottom. During breeding, the male prepares and guards a nest beneath a rock, where the female deposits strings of eggs.
They are sometimes confused with mudpuppies or tiger salamanders, but hellbenders are much larger and spend their entire adult lives in running water. Habitat degradation, siltation, dams, pollution, and disease have contributed to declines across parts of their range.