ST. LOUIS — Inside the Ron Goellner Conservation Center at the St. Louis Zoo, slimy creatures 2 feet long hide under rocks in separate tanks. These solitary creatures are the largest amphibians in North America, giant salamanders known as hellbenders or "snot otters."
Hellbenders have been on the federal endangered species list since 2004.
• The hellbender (Cryptobranchus alleganiensis) is a giant salamander, native to North America.
• They inhabits large, swiftly flowing streams with rocky bottoms. Most can be found under rocks in shallow rapids.
The largest hellbender in captivity was measured at 2 1/2 feet, but most adults are 2-feet long.
• They can live for 30 years, perhaps longer in the wild.
• Hellbenders have been classified an endangered species in Missouri, Illinois, Indiana, Maryland and Ohio, and "rare" or "of special concern" in Georgia, Kentucky, New York, North Carolina, Virginia and West Virginia.
• Since the 1970's U.S. populations have declined an average of 77 percent.
Yet these salamanders, native to streams and rivers, call the Missouri River Valley and Ozark regions home. In fact, Missouri is the only state to have supported both the eastern hellbender and Ozark hellbender.
An estimated 500 hellbenders are left in the wild, and without the proper propagation methods, the creatures will be gone by 2020, according to the Missouri Department of Conservation.
The St. Louis Zoo is a leader in hellbender conservation. The propagation work there is funded by the U.S. Fish and Wildlife Service and the Missouri Department of Conservation.
Through a head-start and reintroduction program, the zoo is working to harvest the eggs, raise the amphibians to maturity and let them loose in the wild. Otherwise, unfavorable conditions in their habitat are threatening the hellbenders' survival.
Hellbenders need clean, cool water to survive, and many waterways are losing the vital ecosystems to support their needs.
Like other amphibians, hellbenders breathe through their skin. They have evolved folds of skin with millions of micro-capillaries that help them take in oxygen from the water.
Mark Wanner, the zoo's manager of reptiles, said the adaptation has proved to be detrimental because the increased surface area of the folds allows the creature to take in more oxygen, as well as more contaminants.
Wanner pointed to a number of factors that contribute to the animals' problems with water temperature and loss of habitat. Endrocine disrupters in water, siltation, insecticides, pesticides, overcollecting and amphibian chytrid fungus have all contributed to problems, Wanner said.
The chytrid fungus is the newest and most serious threat to hellbenders, as well as all amphibians, Wanner said. The fungus attacks the keratin in the nails, feet and mouth of the hellbender. It can cause infertility in males and females and also affects the skin, making it hard for the animals to breathe.
Hellbenders affected by the fungus can be found with open sores and missing limbs, and there is no current treatment.
"We don't know for sure what’s causing all of these abnormalities and missing limbs," said Jeff Briggler, state herpetologist for the Missouri Department of Conservation in Jefferson City, who has been working with hellbenders for 10 years. "We still haven't determined the exact cause of their decline."
Chytrid has been found across the country and in all Missouri waterways. A specialist in Queensland, Australia, Ross Alford, professor of tropical biology at James Cook University at Townsville, said the chytrid fungus is also a threat to amphibians worldwide.
"There's really no continent where amphibians occur nowadays that the fungus doesn't occur," Wanner said.
The fungus may have originated in African clawed frogs sold around the world during the 1930s. Although the frogs were carriers of the fungus, they were not affected by it.
One theory poses that the fungus spread when the frogs were flushed down toilets and deposited in local streams where chytrid became deadly for other species of amphibians.
Another factor in hellbender decline is the presence of endocrine disrupters in river systems. When a person takes a hormonal medication, such as birth control pills, not all of the hormones are absorbed into the body. The remaining hormones are released during urination. Sewage treatment facilities are not designed to remove these hormones, so they remain in the water, flowing into the world's rivers.
These excess hormones affect amphibians directly, said Charlie Scott, the field supervisor at the Columbia Fish and Wildlife Service. Because of its permeable skin, the hellbender is affected even more than the average aquatic animal.
Scott said he believes there is hope for the hellbender through a proposal for polishing wetlands in Columbia. This is an innovative process created in 1990 in which aquatic plants in man-made wetlands help remove chemicals and minerals before water is released into streams. Scott believes the hormones are somehow eliminated in the process, which could be the key to saving the amphibians.
“This fungus is a global threat," Scott said. "It is spreading across the Earth. There are already amphibians extinct in New Zealand and Australia.”
The animals are not safe in captivity, either. Scott said half the population of hellbenders in zoos have died because of exposure to the fungus.
Wanner said losing the hellbender could mean trouble for humans who rely on them for food-chain balance. He hopes to prevent this extinction, and give these animals a fighting chance.
Conservation efforts at the St. Louis Zoo and elsewhere are moving forward quickly to prevent the extinction of the species.
"In the 1970s, several scientists — biologists doing field work with hellbenders — they would find, let's say, 100, 200 a day, on a good day on the river," Wanner said. "Since the 1970s, they've probably declined about 80 to 85 percent, to the best of our knowledge."
"If you lose amphibians, you're gonna probably have a rise in some of the unbeneficial animals, just because amphibians are a huge predator of any of our (aquatic) larval type insects,” he said.
"Once that balance (in the food chain) is disrupted, ... I don't think we really know what that outcome will be. Unfortunately, we may find out one day."