Meet the hellbender: North America's largest amphibian that faces an uncertain future

One Earth’s “Species of the Week” series highlights an iconic species that represents the unique biogeography of each of the 185 bioregions of the Earth.

In the cool, clear rivers of the eastern United States, a creature with prehistoric roots lives mostly unseen. The hellbender (Cryptobranchus alleganiensis) is a fully aquatic salamander that spends nearly its entire life beneath large, submerged rocks in fast-flowing streams. Its flattened body allows it to wedge into narrow crevices, where it lies still for hours, waiting for nightfall to hunt.

Found from southern New York to northern Georgia and west to Missouri and Arkansas, this ancient amphibian is a sign of a healthy stream. If hellbenders are present, the water is likely clean, cold, and rich in oxygen. Exactly what this reclusive species needs to survive.

Unmistakable appearance and unique adaptations

The hellbender is the largest salamander in North America, reaching up to 74 centimeters (29 in) in length and weighing as much as 2.5 kilograms (5.5 lbs). Its flattened body and rudder-shaped tail allow it to navigate strong river currents, while loose folds along its sides increase surface area for breathing through the skin. Though equipped with lungs, hellbenders rely on cutaneous respiration, absorbing oxygen directly from water through capillaries in their wrinkled skin.

This species is often mistaken for mudpuppies, but can be distinguished by its lack of external gills and the five toes on its hind feet. Its eyes are small, its coloration varies from brown to gray to nearly black, and its body is covered in irregular blotches that help it blend with the riverbed.

Where the name “hellbender” comes from

The origins of the name “hellbender” are steeped in folklore. Early European settlers reportedly believed its grotesque appearance evoked visions of the underworld. One theory is that its undulating skin reminded observers of “horrible tortures of the infernal regions,” while another suggests it was “bent on returning to hell.” Despite the dramatic nickname, this reclusive salamander is completely harmless.

Other vernacular names include snot otter, lasagna lizard, devil dog, mud devil, mud dog, water dog, grampus, Allegheny alligator, and leverian water newt.

Its scientific name, Cryptobranchus, is derived from the Ancient Greek kryptos (hidden) and branchion (gill). “Hidden gill,” is a nod to the small gill slits retained by juveniles and the hidden mode of respiration that defines the species.

The art of suction feeding

Hellbenders are nocturnal predators, using smell and water vibrations to detect prey. Their diet consists primarily of crayfish, which they consume in large quantities during the warmer months. In colder seasons, when crayfish become less active, they shift to small fish and aquatic insects.

Hellbenders often use suction to pull in larger prey, opening their mouths rapidly to create a vacuum. They have also been known to cannibalize eggs…sometimes even their own, especially when food is scarce or habitat quality declines.

How hellbenders shape the ecosystem

As both predators and prey, hellbenders help maintain the balance of stream ecosystems. Their presence limits crayfish populations, which in turn affects the availability of food and shelter for other species. In early life stages, they are eaten by bass, snakes, turtles, and otters. As adults, their only real threats come from larger predators like raccoons and minks.

Because hellbenders are highly sensitive to pollution, siltation, and changes in water temperature, they are considered an indicator species. Their long lifespan, up to 30 years in the wild and potentially 50 in captivity, allows scientists to monitor stream quality over time.

A life lived in solitude and father guardians

Hellbenders are solitary and highly territorial. Once a salamander claims a rock, it rarely strays far. During breeding season, from late summer to early fall, males create saucer-shaped nests beneath rocks and wait for females to approach. After mating, the male fertilizes the eggs externally and guards them fiercely for up to two months, fanning water over them with his body to keep them oxygenated.

Females can lay up to 200 eggs, and some nests may contain thousands due to multiple females choosing the same male. Sadly, many eggs do not survive due to predation and environmental pressures. 

Hatchlings emerge about two months later with external gills, which they lose around two years of age. Sexual maturity is reached between six and eight years.

The many threats facing the hellbender

Hellbenders face mounting threats across their range. Habitat loss from dams, deforestation, and mining buries or removes the rocks they need for shelter and nesting. Pollution from agriculture and industry degrades the water quality required for their survival. Misconceptions about the species have led to unnecessary killings, while illegal collection for the pet trade has removed many individuals from the wild.

Emerging diseases like chytridiomycosis and the potentially devastating Bsal fungus pose additional risks. Though not yet found in North America, Bsal has severely impacted salamander populations in Europe and could prove catastrophic if introduced.

Conservation efforts and a glimmer of hope

The IUCN lists the hellbender as Vulnerable, and the Ozark subspecies is federally endangered. Across its range, population declines have exceeded 70% in some areas. Conservation groups and government agencies have launched initiatives to protect and restore hellbender populations.

The St. Louis Zoo successfully bred Ozark hellbenders in captivity for the first time in 2011, and head-start programs in states like Indiana, New York, and Ohio raise hatchlings from wild eggs to be released when they are less vulnerable. In Pennsylvania, students helped pass legislation naming the eastern hellbender the state amphibian to raise awareness about clean water and amphibian conservation.

Research organizations are now using environmental DNA (eDNA) to detect the presence of hellbenders in streams without disturbing their habitat. With increased public awareness and coordinated conservation efforts, there is still hope for the future of these ancient amphibians.

A call to protect our rivers

Hellbenders are not just a quirky oddity of freshwater biology. They are living testaments to the health of the waters they inhabit. Protecting the hellbender means protecting the clean rivers and streams that people, wildlife, and entire ecosystems depend on.

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