TOWNSEND, Tenn. — It would be several hours before the first wave of tubers floated by.
On this summer morning, researchers had the Little River all to themselves. They were in the Great Smoky Mountains National Park in Tennessee looking for hellbenders, the largest salamander in North America, an amphibian whose size is exceeded only by the giant salamanders of China and Japan.
Wearing wet suits, they snorkeled against the current, turning over rocks in the crystal-clear water. A four-inch crayfish — a favourite hellbender snack — scooted across the bottom, and in some places, the snorkelers had to struggle to hold their position.
This summer, investigators with the University of Tennessee and the Knoxville Zoo are collecting hellbenders to test for a pathogenic fungus linked to the sharp decline of frogs and other amphibians throughout the world.
The fungus, Batrachochytrium dendrobatidis, was first identified in 1998 after it caused widespread frog deaths in Australia and Central America. Scientists now believe it may have entered North America as early as the 1970s, and likely was introduced by infected African clawed frogs sold in pet stores and used in research.
The fungus causes a disease that infects not just frogs, but salamanders, too. So far, it has only been identified in the Ozark hellbender, a subspecies from Arkansas and Missouri.
In Tennessee, hellbenders are listed as a species of special concern. They’re found in clean, cool streams throughout the Eastern United States, and they’re considered an indicator species thanks to their sensitivity to siltation and other stream impairments.
Marcy Souza, assistant professor in the Department of Comparative Medicine at the UT College of Veterinary Medicine, said there is no evidence at this point that the fungus has spread to hellbenders in the Southeast.
“At this point, we don’t think they’re susceptible,” Souza said. “It’s a unique species, and if we don’t look, we won’t really know.”
The project’s goal is to collect 50 hellbenders from the Little River in the Smokies and the Hiwassee River in the Cherokee National Forest over the next three summers. So far, they have captured and released 22 specimens, most of them from the Hiwassee.
An hour into the survey, one of the snorkelers caught a juvenile hellbender 5.4 inches long. An inflatable raft carried all the lab equipment. A microchip was inserted under the skin to identify the hellbender in case of a recapture, and they swabbed its skin to test for the fungus.
They also took a tiny skin sample to test for a virus that is contributing to the global amphibian decline.
After they were finished, the research team released the hellbender and resumed their search.
In 2004, an international convention of amphibian experts determined that 32 percent of all amphibian species — frogs, toads, salamanders, newts — are threatened with extinction. By comparison, 12 per cent of birds and 23 per cent of mammals are threatened.
Biologists say the decline has occurred worldwide over the last three decades. In addition to disease, a range of causes including habitat loss, pesticides, climate change and increased ultraviolet radiation are believed to be involved.
Just before lunch, Michael Ogle, a herpetologist at the Knoxville Zoo, nabbed what turned out to be the largest hellbender collected this summer. Through his face mask, he spotted about two-thirds of the body hidden beneath several rocks, with the rest of the hellbender barely exposed.
Hellbenders have earned their share of colorful nicknames, including “mud devil,” “water dog” and “walking catfish.” Grabbing the hellbender, Ogle immediately understood why they’ve also been called “snot otters.”
“It was real slippery,” Ogle said.
A full-grown adult, the hellbender weighed just more than 1 pound and measured 16 inches long. It had blotchy skin and small, beady eyes with starburst pupils similar to a snapping turtle’s. From its flat head to its long, powerful tail, every anatomical detail suggested a creature adapted to life on the bottom of fast-moving streams. One of the team members that morning was Phil Colclough, curator of herpetology for the Knoxville Zoo, ranks hellbenders among his favourite critters.