There are two subspecies of hellbender: the Eastern and the Ozark. Both once inhabited a vast network of Appalachian rivers and streams that drain into the Mississippi River, and both are now rare. Eastern hellbenders are found in small, isolated territories from the state of New York south to Georgia, Alabama, and Mississippi, and westward to central Missouri and possibly southeastern Kansas. The Ozark hellbender is restricted to small sections of southeastern Missouri and northeastern Arkansas.
The eastern hellbender’s range includes a small part of westernmost Maryland. The species exists in very low numbers in the Casselman and Youghiogheny Rivers and their associated tributaries.
You can see eastern hellbenders on exhibit in the Maryland Wilderness section of The Maryland Zoo, near the otters.
Hellbenders prefer fast-running and fairly shallow water, and are most likely to be found underneath large, flat rocks (called flagstones) or logs in riffle areas of streams and rivers. They take cover during the day and come out to feed at night. They are sit-and-wait predators that eat mainly crayfish but also other small aquatic creatures. They suction prey directly into their wide mouths after a strong sideways jerk of the head.
Hellbenders are fully aquatic amphibians, meaning that they live entirely underwater. Oddly enough, they have working lungs and can surface to breathe, but rarely do. Instead, they mostly “breathe,” or respire, by absorbing oxygen from the water directly through their skin. This is known as cutaneous respiration. The wrinkly flaps running along either side of their bodies increase their skin’s surface area, allowing for maximum oxygen uptake.
Eastern hellbenders are stout bodied, with four short, well-developed limbs and a heavy, laterally compressed tail. The body shape and rudder-like tail help to stabilize the animal in moving water.
Nobody really knows where the name “hellbender” came from, but many have speculated that it was a name given to this salamander long ago by those who first discovered it and were horrified by its odd and primitive appearance. The hellbender looks like a creature that emerged from the depths of hell and is bent on returning there, or so the reasoning goes.
Admittedly, hellbenders do not conform to most people’s standards of beauty. They have been given one nickname after another, and most evoke fear or revulsion: snot otter, devil dog, Allegheny alligator, mud devil, to name a few. Appearances aside, though, the hellbender is very well adapted to its particular ecological niche and is entirely harmless. Despite rumors and assumptions to the contrary, hellbenders are not poisonous, do not bite aggressively, and are beneficial contributors to their ecosystems.
Hellbenders and their larvae are vulnerable to large fish, turtles, water snakes, and humans. Adults put up a formidable defense against predation, though, that includes camouflage and slime. Eastern hellbenders are generally described as dark green or gray dorsally and lighter on the underside. Irregular dark spots – brownish or black in color – are often present on the dorsal surface (back). Their coloration helps them blend almost to the point of invisibility into the bottom of a river or stream.
Hellbenders are also quite slimy. They are covered in mucus that is thought to help protect them from abrasion, parasites, and anyone or anything that tries to grab them. When threatened, they also excrete more of this mucousy substance from their skin, and it is vile tasting to many predators. An animal that grabs a hellbender in its mouth is likely to release it!
Eastern hellbenders breed in late summer and early fall. Normally solitary and reclusive, the males leave their regular hiding places and become more active, even during the day, looking for and sometimes fighting over suitable nesting sites. Males excavate saucer-shaped nests lined with gravel that are often protected by some sort of rock overhang. Males sit at the entrances to their nests, guarding against other males and trying to lure eligible females.
Once in the nest, a female may take up to two days to deposit her eggs, and the male will try to keep her there until she does. Females deposit softball-size masses of about 200 to 400 eggs. Males fertilize the eggs externally. Both male and female will sway back and forth in the nest so that eggs and semen mix thoroughly. After laying eggs, females leave the nests voluntarily or are forced out by the males, who stay behind to protect the eggs and eventually the larvae.
Males will accept more than one gravid (i.e. egg-laden) female into their nests, which means that any male ultimately might protect more than 2,000 eggs! Many eggs are lost to predation, including by other hellbenders, but those that survive will hatch after a gestation period of 68 to 75 days. Hatchlings are initially a uniform gray or brown, and are equipped with conspicuous yolk sacs that provide nourishment for the first few months of life.
Hellbender populations have been in steep decline for several decades now. Overall numbers are dropping, and those populations that remain are having trouble growing. For whatever reasons – and there may be several – there seem to be fewer and fewer juveniles surviving to adulthood.
Scientists studying hellbender decline have identified likely causes but have not yet determined each one’s degree of impact, or the overlapping effects of all. Still, it can be stated fairly that human impact on hellbender habitat in recent decades has hurt the species. Hellbenders, like all amphibians, are extremely sensitive to environmental change and habitat alteration. This is why amphibians are known as environmental indicator species. They will register the impact of a positive or negative environmental change sooner than most species. With hellbenders, changes to water quality and flow have proven detrimental. Damming, channeling, and dumping silt into waterways (a frequent consequence of nearby logging and land development projects) slow the flow of water, making a stream or river less desirable or livable for hellbenders. Pollution caused especially by coal mining and agriculture also has been identified as a cause of severe habitat degradation. To put it simply, hellbenders must have clear, clean, swift water in order to survive. Any change to their water impacts them and their survivability significantly.
Emerging diseases and the introduction of game fish species that can prey upon hellbender larvae and juveniles also may be taking their toll on hellbender populations, but to what extent nobody yet knows.
Many states, including Maryland, have given hellbenders protective status, but these salamanders are not yet listed as federally threatened or endangered. Should they be given federal status, it would open the way for land development regulations that could meaningfully protect hellbenders and their habitat.