Description The largest salamander in North America. This completely aquatic species reaches adult sizes of 24 to 40 cm snout to vent length (30-74 cm total length) (Dundee and Dundee 1965; Dundee 1971; Petranka 1998).
These salamanders are excessively slimy and are dorso-ventrally flattened. The head is broad and the eyes are tiny and lidless. The large, paddle-like tail is laterally compressed. The skin is loose and wrinkled. The limbs have flaps on the posterior edges, and there is a floppy lateral fold of skin. Adults have a single gill slit on either side of the head and lack external gills. Larvae are stream type with small gills and a low tail fin. Hatchlings are are 25-33 mm total length. The limbs are incompletely developed at hatching (Dundee 1971; Nickerson and Mays 1973; Petranka 1998).
Adult coloration is greenish, yellowish brown or slate gray with black spots or blotches (Petranka 1998).
Two subspecies are recognized based on differences in geographic distribution (see below) and coloration. Cryptobranchus a. alleganiensis, the Eastern hellbender, has small dark spots dorsally and a uniformly colored chin. Cryptobranchus a. bishopi, the Ozark hellbender, has larger black blotches dorsally and a darkly mottled chin region. The spiracle opening is also smaller in C. a. bishopi (Dundee and Dundee 1965; Dundee 1971; Nickerson and Mays 1973; Petranka 1998).
Small larvae are uniformly dark dorsally with a white venter. Older larvae have dark spots dorsally and pigmented venters (Petranka 1998).
U.S. state distribution from AmphibiaWeb's database: Alabama, Arkansas, Georgia, Illinois, Indiana, Kentucky, Maryland, Missouri, Mississippi, North Carolina, New York, Pennsylvania, South Carolina, Tennessee, Virginia, West Virginia
Hellbenders occur from New York to northern Alabama and extreme northeastern Mississippi, and westward to central and southern Missouri and northern Arkansas (Petranka 1998).
Principally associated with tributaries of the Ohio and Tennessee rivers west of the Appalachian Mountains. Disjunct populations occur in the Susquehanna River (New York, Pennsylvania), the upper Savannah River (Georgia), and tributaries of the Missouri and Black rivers (Missouri, northern Arkansas) (Dundee 1971).
Cryptobranchus a. alleganiensis occurs in central Missouri and from southern New York south to northern Alabama and a small portion of Mississippi. Cryptobranchus a. bishopi ocurs in southern Missouri and adjoining portions of Arkansas (Petranka 1998).
The preferred habitat is large streams and rivers with fast-flowing, clear water and a rocky substrate. Individuals are most easily found under large boulders. Water temperature is usually cold (20º C, sometimes as high as 25-30º C) and fairly constant through the year (Dundee 1971; Petranka 1998).
Life History, Abundance, Activity, and Special Behaviors Hellbenders usually breed in the late summer and early fall (September), but eastern hellbenders may breed two months or more earlier than Ozark hellbenders (Dundee and Dundee 1965; Nickerson and Mays 1973; Peterson 1988).
Hellbenders form breeding aggregations in and around nest sites, such as burrows in streamside banks or under large rocks. Males compete for access to mates (Nickerson and Mays 1973; Peterson 1988).
Similar mating behavior has been observed in Andrias japonicus, the Japanese giant salamander, another member of the family Cryptobranchidae (Kawamichi and Ueda 1998).
Fertilization is external, and chemical cues may be important in courtship and mating (Peterson 1988).
Nests have been found containing from 138 - 334 eggs, and a female laid 200 eggs in captivity. Females may share oviposition sites, and over 1900 eggs have been found in a single nest. Males tend the eggs after oviposition and fertilization, and they guard against egg predation by conspecifics (Petranka 1998).
Hatching occurs in late fall after a developmental period of 45 - 75 days, depending on locality (Peterson 1998; Petranka 1998).
Hellbenders forage at night, sometimes on overcast days, and they retreat to crevices under rocks during the day (Nickerson and Mays 1973).
The diet is varied including crayfish, small fish, mollusks, and worms. The slime produced by these animals is noxious to many predators, but they are occasionally preyed upon by large fish, turtles and water snakes. Eggs and larvae are frequently eaten by conspecifics. See Petranka (1998)
for references. Hellbender densities have been estimated at over 400 animals/km of stream, and up to 10 animals/100 m2 (Nickerson and Mays 1973; Peterson 1988).
Hellbenders are fairly long-lived and may reach ages of 20-30 years in the wild (Petranka 1998).
Trends and Threats Siltation and pollution, including thermal pollution, are threats to populations of C. alleganiensis (Dundee 1971; Petranka 1998).
Relation to Humans Many fisherman consider hellbenders to be poisonous and will cut their line rather than unhook them (Conant and Collins 1991).
Native Americans traditionally used this species as a food source (Petranka 1998).
Possible reasons for amphibian decline
General habitat alteration and loss Dams changing river flow and/or covering habitat
Comments Some authors have suggested that the two currently recognized supspecies should be treated as separate species. The ranges apparently do not contact, and the morphological differences suggest reproductive isolation and absence of gene flow between the forms (Collins 1991).
This species was featured as News of the Week on 4 February 2019:
Eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) are entirely aquatic, giant salamanders, which inhabit fast-flowing streams in North America that have clean water and rocky bottoms. Eastern hellbender populations have been experiencing tremendous declines and are currently being considered for listing under the U.S. Endangered Species Act. Wineland et al. (2018) evaluated eastern hellbender population persistence in West Virginia, a poorly studied portion of the species’ range. Using environmental DNA (eDNA), they found that over a third of sites in West Virginia that historically harbored hellbenders no longer do. Of the locations where hellbenders remained, many were in or near the Monongahela National Forest. Statistical models by Wineland and colleagues further suggested a higher density of roads surrounding historical populations may have led to population declines and extirpations. This is likely because roads and other impervious surfaces release substantial runoff that degrades water quality and alters stream flows. This work using eDNA highlights the importance of minimizing future landscape development while also protecting existing forests and reforesting degraded terrestrial landscapes to protect highly sensitive freshwater amphibians like imperiled hellbenders (Written by Max Lambert).
Collins, J. T. (1991). "A new taxonomic arrangement for some North American amphibians and reptiles." Herpetological Review, 22, 42-43.
Conant, R. and Collins, J. T. (1991). A Field Guide to Reptiles and Amphibians: Eastern/Central North America. Houghton Mifflin, Boston.
Dundee, H. A. (1971). ''Cryptobranchus, and C. alleganiensis.'' Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles, 101.1-101.4.
Dundee, H. A., and Dundee, D. S. (1965). ''Observations on the systematics and ecology of Cryptobranchus from the Ozark Plateaus of Missouri and Arkansas.'' Copeia, 1965(3), 369-370.
Kawamichi, T. and Ueda, H. (1998). ''Spawning at nests of extra-large males in the Giant Salamander Andrias japonicus.'' Journal of Herpetology, 32, 133-136.
Nickerson, M. A., and Mays, C. E. (1973). The Hellbenders: North American ''Giant Salamanders''. Milwaukee Public Museum, Milwaukee, WI.
Peterson, C. L. (1988). "Breeding activities of the hellbender in Missouri." Herpetological Review, 19, 28-29.
Petranka, J. W. (1998). Salamanders of the United States and Canada. Smithsonian Institution Press, Washington D.C. and London.