Four years ago 41 hellbender salamander larvae from western New York State arrived at their temporary home in New York City. Originally collected as eggs near the Allegheny River, the hellbenders—also known as snot otters or devil dogs—were hatched at the Buffalo Zoo and then transferred to the Wildlife Conservation Society's Bronx Zoo, where they were placed in an isolated, specially built facility. Tiny at the time, the animals have since grown to about 30 centimeters in length, roughly half their eventual size. Last week 38 of the hellbenders were driven six hours from the Bronx and rereleased back into their native habitat.

The release is the latest step in an effort to help boost the wild population of the eastern hellbender (Cryptobranchus alleganiensis alleganiensis), a threatened subspecies of giant salamander that is not yet endangered but faces a shrinking population and what appears to be a dangerously low birth rate in the wild. "We don't have a lot of recruitment of young animals," says Don Boyer, the Bronx Zoo's curator of herpetology, who has watched the hellbenders grow since he joined the organization two years ago and who took the recent journey to western New York for the animals' release. "It seems like the younger stages of the hellbender are more vulnerable," Boyer says. "The head-starting, while it's not a solution, may help get the hellbenders through that critical juvenile phase and put them back in the system."

Boyer explains that multiple factors have probably contributed to the eastern hellbender's decline. The animals depend on clean, cold water and streams with large, flat rocks under which they can hide. Road construction and agricultural practices have muddied the water of many rivers and streams, adding silt that makes it harder for the hellbenders to thrive. Dams and other construction have destroyed habitats or made rivers less hospitable. "If the river gets shallow, it can heat up, because there's less water," Boyer says. Chemicals such as atrazine, the popular herbicide, have also caused problems. "Some chemicals can act as endocrine disruptors and interrupt various phases of hellbender development," he says. "We know it can be a problem for other amphibian populations." Hellbenders have also historically faced persecution (because who won't be threatened by a 75-centimeter salamander?) and overharvesting for the illegal pet trade.

Raising the hellbenders in captivity required carefully mimicking many of their natural conditions. The zoo built a special system that kept the hellbenders' water as clean and cold as a mountain stream. Temperatures and lighting shifted as the seasons changed. "The Bronx Zoo has a really great life-support systems technician who was able to design the system," Boyer says. "The whole thing worked really well."

The hellbenders were not put on exhibit and were kept away from other amphibians in the zoo's collection. "We keep them in a biosecure facility so they're not exposed to novel amphibian pathogens from other parts of the world," Boyer says. Even so, the hellbenders were all tested for diseases and the amphibian-killing chytrid fungus before release. They were also implanted with microchips so biologists studying the subspecies can identify any of the hellbenders they reencounter in the Allegheny Basin.

Although the zoo won't be involved in monitoring the released animals, it may put the three remaining hellbenders on display, and zoo staffers anticipate head-starting another population soon. "We're hoping there will be some eggs harvested this fall," Boyer says. "We'll get some of those fertilized eggs and hatch them at our facility and head-start an even bigger round of hellbenders. We're thinking we can probably do 200 hellbenders next time." That may not solve the problems affecting hellbenders in the wild, but it's a good step for these slimy wonders.

Photos by Julie Larsen Maher, courtesy of the Wildlife Conservation Society

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