Hellbenders are large aquatic salamanders. They have a wide, flat head with tiny eyes and a broad and vertically compressed, rudderlike tail. The body and legs are covered with prominent folds of skin.
Missouri is the only state that contains both recognized subspecies of North American hellbenders. Both have experienced marked declines and are species of conservation concern. The current taxonomy of hellbenders will likely be changed soon with the elevation of additional species and subspecies.
The Ozark hellbender (subspecies) is a large, permanently aquatic salamander that has a broad and flattened head with small, lidless eyes. The sides of the body, and often the legs, have pronounced wrinkled folds of skin. The tail is vertically flattened and rudderlike. A gill opening, although often hidden, is located on each side of the head. Body color varies from gray brown to olive green with large dark markings and blotching in both juveniles and adults. Black or dusky markings over a large part of the lip and chin are often present. The belly is a uniform dark tan or gray brown and is lighter in color than the rest of the body.
Similar species: The eastern hellbender subspecies (Cryptobranchus alleganiensis alleganiensis) is very similar. Its adult size averages slightly larger (13–23 inches) (as opposed to 10–21 inches for Ozark hellbender); it is gray to reddish brown above, and the body is uniform in color, with few to no dark markings. Perhaps the easiest way to distinguish it is by its different geography: it occurs in north- and northeast-flowing rivers in the northern Missouri Ozarks (as opposed to south-flowing rivers in the southern Missouri Ozarks).
Also similar to hellbenders are mudpuppies (Necturus spp.); mudpuppies, however, have external gills, which are red and plumelike, behind the head on both sides. They have 4 toes on each foot. As adults, mudpuppies reach only 8–13 inches in length. Hellbenders lose their external gills once they reach 4 or 5 inches long, they have 4 toes on the forelimbs and 5 toes on the hind limbs, and their total length may reach 24 inches.
Adult length: usually 11–21 inches; they have been known to reach 22 inches. (Thus, on average, they are slightly smaller than the eastern hellbender subspecies.)
The Ozark hellbender (subspecies) is restricted to the southern Ozark Highlands in spring-fed sections of the Black River system and the North Fork of the White River system. Globally, this hellbender only occurs in southern Missouri and adjacent sections of northern Arkansas. Its distribution is different from that of the eastern hellbender subspecies and thus is a key ID character.
Habitat and Conservation
Hellbenders are well suited for an aquatic existence. The flattened head allows this salamander to crawl under large rocks or within bedrock crevices along the stream bottom. Its streamlined body reduces water resistance, allowing easier movement while walking on the river bottom. Numerous wrinkly folds of skin along its sides provide increased surface area for respiration.
Ozark hellbenders prefer rivers cooled by natural springs that contain large amounts of limestone rock for shelter. Some of the largest known populations of hellbenders were historically found in southern Missouri streams. Because of their nocturnal and secretive behavior, these salamanders are seldom observed by the casual visitor of Ozark streams.
Hellbenders are declining and are listed as an endangered species. They need clean, clear, cool rivers to survive, and they should never be harmed or removed from the wild.
Hellbenders mainly feed on crayfish, although small fish, snails, and insects are occasionally eaten. Little is known of the food choices of larval Ozark hellbenders. In the wild, they apparently feed on various aquatic insects similar to the eastern hellbender.
Both subspecies of hellbenders that occur in Missouri are listed as endangered by both the state of Missouri and by the federal government. They may become extinct in our state in less than 20 years. None may be taken from the wild for any use. Ozark hellbenders are often caught by anglers. If caught on hook-and-line, hellbenders should be released unharmed.
Recent surveys of Missouri’s populations of Ozark hellbenders have shown a 70 percent decline, with little to no observations of young individuals. The specimens observed were larger, older adults. Because of these findings, the Missouri Department of Conservation classified the Ozark hellbender as state endangered in 2003. In 2011 the U.S. Fish and Wildlife Service listed it as a federally endangered species.
The primary threats to this salamander are habitat alteration and degradation, over collecting, disease (mainly amphibian chytrid fungus), predation, and degraded water quality. Hellbenders are long-lived, slow-to-mature amphibians that seldom venture far within the river; therefore, changes in substrate conditions where increased sediment eliminates rocky habitat should be avoided. Because of the significant population decline of the Ozark hellbenders and the threats they face, hellbenders are being zoo bred and reared at the Saint Louis Zoo. The animals raised at the Saint Louis Zoo are being released back into their native river to ensure the Ozark hellbender remains a part of the Missouri landscape.
Taxonomy: Recent genetic studies seem to show that the eastern hellbender and the Ozark hellbender should both be elevated to full species status.
These fully aquatic salamanders take in oxygen through their skin. By day, they hide under large flat rocks; by night, they walk slowly along the stream bottom, hunting.
Breeding is mainly in October, with adults walking on the bottom of the river to move to breeding sites. Fertilization is external, about 80–350 eggs may be deposited into the nest, and the males guard the eggs. The eggs hatch in about 45 days. The larvae lose their external gills after about 1½ or 2 years.
Hellbenders are a major indicator of the overall health of a river or stream. If there is something in the water causing their numbers to decline, it can affect other species as well, including us.
In 2019, the hellbender was designated as the official endangered species for the state of Missouri. At the time that legislation passed, Missouri had 70 species of plants and animals listed as state-endangered, 27 species on the federal endangered list, 15 species on the federal threatened list, and 1 species being considered as a candidate for federal listing.
A number of organizations, including MDC, are partnering with the Saint Louis Zoo in a captive breeding program for hellbenders, reintroducing them into the wild, with an aim to increasing their numbers in wild populations and ensure this animal remains a part of Missouri's biodiversity.
Hellbenders are part of a healthy natural aquatic environment, and they play an important role in maintaining crayfish populations.
Hellbenders have been on our continent for more than 6 million years and are a unique part of our wildlife heritage.
North America's hellbenders are members of only two genera in the family Cryptobranchidae. The other genus, Andrias, occurs strictly in Asia and comprises only two living forms, the Chinese and Japanese giant salamanders (A. davidianus and A. japonicus, respectively); members of the Asian genus may grow to 5 feet in length. The Chinese species is critically endangered.