Park embarks on cutting-edge hellbender study

With wrinkly skin that comes in various shades of brown, eastern hellbenders aren’t easy to spot. These giant salamanders, which average 20 inches in length, spend most of their lives nearly invisible under rocks on the bottom of cool, fast-flowing streams. In a two-year research project starting this summer, Great Smoky Mountains National Park will use a combination of cutting-edge technology and traditional survey techniques to solve the mystery surrounding the hellbender’s distribution in the Smokies.

“One of the major conservation questions is: Are hellbenders reproducing in our streams?” said Jonathan Cox, wetlands biology technician for the park. “And it’s really hard to find that out because their lifespan is so long that you can have a hellbender detected in a stream for multiple decades, but it may be the same individual.”

Hellbenders can live for 30 years or more, so figuring out whether the adults alive today are reproducing successfully is imperative to securing the species’ future. Hellbender populations have declined significantly over recent decades, leading the US Fish and Wildlife Service to propose that the salamander be listed as an endangered species. A public comment period on the listing proposal is open through February 11.

Data supporting the proposal was gathered prior to Hurricane Helene, which wildlife biologists believe had a devastating impact on hellbender populations in Western North Carolina and East Tennessee, home to some of the healthiest across its range. Though many of the park’s streams are too high in the watershed to provide the volume of water hellbenders need to thrive, the Smokies, which escaped the worst of the hurricane’s fury, still hosts some robust hellbender populations. Given the damage Helene wreaked in neighboring communities, Smokies streams, which are supplied by clean water flowing down from the park’s highest peaks, have become even more critical to the species’ survival.  

“The park is an important reservoir of genetic diversity and healthy habitats and populations that will always be protected and is protected at the highest levels of the headwaters,” said JJ Apodaca, executive director of the Amphibian and Reptile Conservancy, a nationwide nonprofit that supports conservation in the US.

Cox and Apodaca will be closely collaborating on the upcoming research project, which is expected to last for two years and is funded through a $140,000 allocation from the National Park Service’s Natural Resource Condition Assessment Program. Under direction from NPS, Amphibian and Reptile Conservancy researchers will survey hellbender populations within the park and compare their results to baseline data gathered in the early 2000s.

Some new data will be gathered using traditional techniques—snorkeling in wetsuits to search for hellbenders underwater—but the researchers will also be developing a new technique that could greatly decrease the effort involved in surveying hellbender populations, while also multiplying the usefulness of the data.

This method, called environmental RNA, or eRNA for short, involves analyzing genetic material found in water samples from streams thought to contain hellbenders. The process is similar to eDNA, itself a new technique that researchers have been using for several years to identify individuals of a particular species in a given sample. However, while DNA reveals the genetic material that separates one individual from another, RNA goes a step further to show which genes are expressed. By analyzing eRNA, researchers hope to screen samples for specific gene expressions—such as those found only during the hellbender’s larval stage, like tail fins and external gills.

“Through this method, we’ll be able to collect a water sample and say, ‘Yes, there’s larvae in the stream,’ or ‘No, there isn’t,’” Cox said. “It should hopefully be a really good management tool for conservation, and not just in the park.”

If Cox and Apodaca are successful in their use of eRNA, wildlife agencies across the country could benefit from the techniques they develop—as would the hellbenders under their care. At the North Carolina Wildlife Resources Commission, wildlife biologist Lori Williams said that she and one technician are the agency’s only two employees tasked with working on mountain amphibian populations in Western North Carolina.

“I’m all for any technique that we can scale up to make our work more efficient and reveal meaningful information about hellbender populations,” she said.

Currently, the best way to survey for hellbenders is to search for them while snorkeling in the cold water, said Chris Ogle, biodiversity survey manager for the Tennessee Wildlife Resources Agency. It’s a difficult and labor-intensive process, and much-smaller juvenile hellbenders are especially difficult to spot during these surveys. The emerging eRNA technique could prove helpful in those efforts.

“Science is always progressing with new and updated features that allow you to do things more passively, which is a great thing for efficiency but also because every time we put hands on the animal, that’s putting stress on the animal as well,” Ogle said. “A lot of times, that’s the only way to monitor how their populations are doing.”

The Smokies project will seek to answer other hellbender-related questions as well, analyzing the DNA of captured animals to determine their genetic lineage and ascertain whether some populations are becoming isolated, leading to genetic bottlenecking and inbreeding.

“If we know that those streams’ populations are experiencing reduced genetic diversity from geographic isolation, that might change our decision-making when weighing NPS operations like building a new trail or road and bring more intense conservation actions onto the table, like translocations and reintroductions,” Cox said.

He’s particularly interested in the state of hellbender genetics near Fontana Dam, which cuts off the natural flow of streams leaving the park’s southwestern side. Hellbenders aren’t known to travel far during their lives—according to the USFWS, the average home range is between 322 and 23,810 square feet, smaller than half a football field—and dams are thought to be impenetrable barriers to the species’ natural dispersal.

“The last record we have of hellbenders on that side of the park is from 2015 or 2016, so we don’t actually know that they’ve been in any of those streams over the last decade,” Cox said. “Some subject matter experts think they may no longer be over there.”

The project will also take a close look at the Deep Creek area, home to a known population of hellbenders. Anecdotal evidence from the 2010s suggested that activities such as trampling, rock stacking, and damming—all associated with tubing, a popular activity on Deep Creek—might be resulting in death or loss of limbs for hellbenders; researchers will attempt to find out if that’s the case.

“When you see a hellbender, it’s hard to believe that an animal like that exists,” Apodaca said. “But it fits so well into the Southern Appalachians and really represents the region. It’s a good mascot for how ancient these mountains are and how special that biodiversity is.”

But that biodiversity is under threat, as the listing proposal indicates and Helene’s aftermath highlights. Many hellbenders died in the flood, and others passed away later, after their attempts to escape the roiling floodwaters left them stranded without the moisture they needed to survive. Cox is worried that a future flood could flush the park’s hellbenders too far downstream for them to return, leading to extirpation in parts of the Smokies.

It’s unknown how hellbenders fared in Cataloochee, Big Creek, and Raven Fork, the areas of the park that endured the worst damage from Helene. These areas would appear to hold quality hellbender habitat but have no known populations. Some have undergone eDNA surveys but came up negative. The upcoming study will give Cox a more solid baseline to compare against any future floods or other events that shift Smokies hellbender populations.

When completed, the study will join a growing body of research from dedicated scientists looking for ways to better monitor hellbender populations, improve their habitat, and help them reproduce successfully. Despite the challenges facing the species, this gathering constellation of data leaves Cox optimistic.

“I think there’s a lot to be hopeful with on hellbenders,” he said. “There’s so much good research being done, so I think the future is bright in that sense. With all of this research, I think we’ll be able to make a big difference.”