Hellbender

Eastern Hellbender

Photo obtained by Dr. Robert Sprackland and the Virtual Museum of Natural History

SCIENTIFIC NAME: Cryptobranchus alleganiensis alleganiensis

OTHER NAMES:  Mudpuppy, Mud-dog, Waterdog, Devil Dog, Allegheny Alligator.

DESCRIPTION:  Eastern Hellbender is a large, totally aquatic salamander (20-74 cm [12-29 in] long).  Adult females tend to be larger than males.  The head and body are flattened, dorso-ventrally.  The tail is long and flattened from side to side, with a distinct keel.  Hellbenders have four short, but well developed legs.  Each foreleg has four toes while the hind legs have five toes each.  The toes of a hellbender end in a rough pad that aids in traction as it moves along stream bottoms.  Loose skin folds extend along each side between the front and hind leg.  The folds of skin are used in respiration; capillaries in the folds diffuse oxygen into the blood.  Larval Hellbenders have external gills.  At approximately 18 months of age, larval hellbenders go through a complete metamorphosis, at which time they loose their gills.  Adult Hellbenders usually retain a single pair of external gill openings on either side of the neck.  Hellbenders have very small eyes located on the top of the head that can detect light but are not very good for forming images.  Coloration typically varies from brown to grayish overlaid by irregularly shaped dark blotches.  Some individuals have brownish to yellow-orange blotches.  The belly area is typically lighter in color, with few markings.

DISTRIBUTION:  Southern New York to northern Georgia and Alabama, and extending westward through southern Ohio to southern Illinois, western Kentucky and Tennessee and northeastern Mississippi.  Disjointed populations of Hellbenders also occur in Missouri and northern Arkansas.  Hellbenders found in these areas represent a distinct subspecies, the Ozark Hellbender (C. a. bishopi).  In Alabama, the Eastern Hellbender (C. a. alleganiensis) is restricted to the Tennessee River drainage system.

HABITAT:  Hellbenders are normally found in medium to large, fast flowing streams and rivers with rocky bottoms and relatively clear water.  Small creeks are occasionally inhabited, especially during the months of September through April.  Riffle areas and upper pool reaches are most often preferred.

FEEDING HABITS:  Hellbenders emerge at night to forage for food using the lateral line system to detect its prey.  Crayfish comprise the bulk of their diet, with small fish, salamanders, and aquatic invertebrates (worms, insects, mollusks) comprising the remainder.  Prey items are captured by means of suction feeding.  Fishermen occasionally report catching Hellbenders on minnows or earthworms.

LIFE HISTORY AND ECOLOGY:  Eastern Hellbenders are well adapted to moving stream environments.  Their flattened heads and bodies tend to prevent them from being swept away in heavy currents.  Hellbenders prefer to walk along the bottom and their powerful tails aid them when moving against a current.  Hellbenders flattened heads also make it easier for them to crawl under flat rocks, ledges and logs that serve as daytime shelters.  The availability of appropriate shelters has been reported as a limiting factor in some Hellbender populations.  Adults will defend a shelter, especially males during the breeding season.  Males and females are known to cannibalize Hellbender nests, including their own.  Breeding season lasts from September through early November in Alabama.  During August, males dig shallow depressions under some form of overhead cover.  Gravid females are either attracted to or corralled into nest sites by the males.  Females simultaneously deposit two long strings of eggs, in a softball-sized yellowish mass onto the nest bed.  Several females may lay in the same nest.  Eggs are fertilized externally as they are being deposited.  The eggs range from 5-7 mm in diameter and number between 130-450 per egg mass.  Males then drive out the spent females and remain within the nest site to brood and safeguard the eggs until they hatch, some two to four months later.  Brooding males may rock back and forth, or undulate their skin folds to increase water flow over the eggs.  Larvae at hatching are approximately 25-32 mm (1-1 ¼ in.) long and retain a large yolk sac.  Little of larval habits and survivorship is known, as very few are ever encountered in the field.  Hellbenders become sexually mature in approximately 5-7 years and can live up to 30 years.

Folklore has it that Hellbenders smear fishing lines with slime, drive game fish away, and inflict poisonous bites.  Despite its large size and rather repulsive appearance Hellbenders are not poisonous.  They avoid game fish altogether, as they would risk being eaten otherwise.  This unfounded folklore has lead to unwarranted persecution of this species by the uninformed.

REFERENCES:

Cline, J. R.  2004.  Eastern Hellbender Cryptobranchus alleganiensis alleganiensis.  Pp. 20-21 in R. E. Mirarchi, M. A. Bailey, T. M. Haggerty, and T. L. Best, eds.  Alabama Wildlife, Volume 3, Imperiled amphibians, reptiles, birds and mammals.  The University of Alabama Press, Tuscaloosa.

Herman, J. 2000. “Cryptobranchus alleganiensis” (On-Line), Animal Diversity Web. Accesses April 12, 2005 at animaldiversity.ummz.umich.edu.

Mount, R. H., 1975.  The Reptiles and Amphibians of Alabama.  Ala. Agri. Expt. Sta., Auburn Univ., Auburn, AL.  347 pp.

Author: Ron Eakes, Wildlife Biologist, May 2005