Eastern hellbenders are the largest salamander in North America. Adults can reach 29 inches in length, though most individuals are typically 11-24 inches long. The hellbender has short limbs and a widely flattened head and body. A fleshy fold of skin extends along the sides of the body between the front and hind limbs, giving them an overall wrinkly appearance. This bunched up skin has led some to refer to the hellbender as "old lasagna sides."
Hellbender body color varies from greenish to yellowish brown with dark spotting along the back and tail. Although adults are quite large, they are rarely seen since they spend most of their time hiding beneath large, flat rocks during the day. At night they forage for crayfish.
Young (larval) hellbenders differ from adults in several ways: they possess external gills, visible yolk sacs, and lack functioning limbs. Newly hatched larvae are generally less than an inch in length. They are typically uniform in color with a dark back and light belly. Larvae rely on their yolk sacs for nutrition for the first several months of life before slowly switching to small aquatic insects (macroinvertebrates). The young remain in the larval stage for approximately two years before undergoing a partial transformation.
This transformation changes their physical appearance as well as their beahvior. Dorsal spotting begins to form at 6 months (~2 – 2.5 inches) and becomes more prominent when the hellbender reaches one to two years of age (~4 – 5 inches). This is also when the external gills are lost. The small, transformed juveniles will spend the next few years hiding under small stones in gravel beds. They will require another three to four years to reach sexual maturity.
Hellbenders are long-lived compared to other amphibians, typically surviving for more than 30 years!