Hellbenders are easily recognized by their dorso-ventrally flattened bodies, flat heads, and fleshy folds of skin along the sides of their body. They attain lengths of up to 74 cm and can weigh more than 1 kilogram. Hellbenders are usually brown to gray with darker blotches on their backs, but in some West Virginia streams a high percentage of individuals are bright orange in color. They hide under large, flattened rocks during the day and become very active at night, walking the stream bottom in search of crayfish beginning just after the onset of darkness.
Hellbenders require very specific habitats.
These include fast flowing, clear, cold, and clean streams with numerous large rocks and very little siltation. Courtship, nest building, and egg deposition occurs in late August to early September in West Virginia. During the breeding season, the male digs a nest under a large rock and waits at its entrance for a female. Fertilization takes place externally. After the female has deposited her eggs under the rock she leaves and the male guards the nest until hatching.