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. They sometimes eat their own eggs and egg predation by other hellbenders may be common. The eggs are deposited in strands of several hundred and are about 2-3 cm in diameter. Hellbenders were probably once very common in West Virginia, though their range has probably been greatly diminished by alterations to stream ecosystems by humans. Many of the streams in West Virginia apparently only contain small, isolated populations of hellbenders associated with areas of remaining rapids due to heavy siltation in other areas of such streams.