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The Chattanooga Zoo’s Hellbender Project is about the whole ecosystem.
We work with this species at the Chattanooga Zoo and we study it in the wild. It is an aquatic ambush predator that’s resided in the waterways of Eastern North America for at least 7 million years, and its predecessors in Asia for 170 million or more. Its two closest relatives survive today in China and Japan. It does not have gills and does not put the rudimentary lungs it does have to much use.
This prehistoric creature was more widely known a generation ago, when people lived a little closer to the land, and when there were much larger populations of the North American Giant Salamander—better known as the Hellbender.
Hellbenders are also known as Allegheny Alligators, Snot Otters and Devil Dogs. The largest specimen ever recorded was 29 inches long and was caught in the Smoky Mountains in the 1930s. The United States is home to two varieties of Hellbender. We have the more abundant (relatively speaking) Eastern Hellbender here in Tennessee. Missouri and Arkansas are home to the endangered Ozark subspecies which, at this point, is only found in three streams.
Hellbenders are a largely forgotten species. To those of us that work with them, it certainly seems like bad timing—as people have spent the last few decades losing their knowledge of wild things, Hellbender populations have simultaneously undergone catastrophic population collapse throughout most of their range.
There are many things that have contributed to this collapse: pollution, acidification of streams from mining activities (think Ocoee River and North Chickamauga Creek), and the notion that they were bad for fish populations. Those are certainly unfortunate, but the single worst contributing factor has been siltation; in other words, dirt and soil running off into our streams. Human activities throughout the last century in agriculture, logging and construction have turned many clear, cool, rocky-bottomed streams into mud-filled ditches. Creeks and rivers in the Tennessee Valley look nothing like they did a century ago.
This is important to the Hellbender for many reasons. First, they find refuge underneath large rocks on stream bottoms. This is where they defend themselves, ambush their prey, lay their eggs, and guard their young. As our streams have filled with mud, the diversity of fish and aquatic invertebrates has decreased. Mud has infiltrated many of the old swimming and fishing holes in streams all over the Tennessee Valley, and as those streams became shallower, water temperatures got higher. Since they have no gills and don’t use their lungs, Hellbenders absorb the oxygen they need through their skin. Higher temperatures in streams means lower oxygen content, which is bad for benders—and many other species.
Yet, you can still find Hellbenders in these severely compromised streams. They can survive in them, but there are not enough places for egg laying, nor rocky habitat for the small offspring. So an adult population dwindles over time, a few solitary individuals lingering for decades, until at last, they pass on. Such is the situation for most of the population in our region. There were robust populations in Middle Tennessee as recently as the 1980s, the streams coming out of the plateau, and the Tennessee Valley historically would also have had good populations.
Now, the Hellbender is what we call functionally extinct over most of the region. Northeast Mississippi, Northern Alabama, and Northwest Georgia have also seen the species vanish.
I grew up hearing stories from my father about catching them in South Chickamauga Creek. Every time we crossed South Chick on Brainerd Road, I’d crane my head to look down into the creek from the car window, hoping to catch a glimpse of one. In 2010, a young fisherman caught one in the South Chick in North Georgia. I went to see it and verify what it was, then let the Georgia Department of Natural Resources know about it. They were excited because this was the first record of the species in that stream in 50 years. We followed up together and did surveys in the area but didn’t find any others.
For nearly a decade, study on the part of many academic field biologists and zoo herpetologists has tried to assess the status of our wild populations. The Chattanooga Zoo has been part of this field research effort since 2009. At this point, our state has six streams, that have healthy, self-sustaining, populations of Hellbenders. As a matter of perspective, though, these are relatively small sections of these streams. String all of Tennessee’s high-quality sections of Hellbender habitat together, and the distance would not reach from Chattanooga to Cleveland, Tennessee. All six of these streams are in the mountains along our border with North Carolina, the last stronghold of Eastern Hellbenders.
The streams and rivers of the Appalachian Mountains, especially in North Carolina, are some of the most protected streams in our country. That’s why there are still good Hellbender populations there. Bad practices in regards to watersheds are everywhere, though, and North Carolina is no exception.
What makes extreme East Tennessee, Northeast Georgia and Western North Carolina such good habitat? Without question, it is the fact that these are National Forest lands with large amounts of intact forest cover, that have a higher degree of protection—but logging and resource extraction are still threats. We were able to showcase Tennessee’s great habitat last year when we co-hosted the sixth meeting of the Hellbender Symposium along with Lee University and the Nashville Zoo. Ninety-five Giant Salamander researchers from across the U.S. and Japan came to Chattanooga to spend time in the field and share the latest in their research.
Something that we do not hear enough about around here is our native biodiversity. We have more species of animals and plants here where we live, than anyplace else on Earth outside of the tropics. That’s why snorkeling in our best rivers is like reef diving—the fish diversity is amazing. The Southeast is the global center for crayfish, salamander and freshwater mussel species diversity. But our rich ecology is not defined by park boundaries, and extinction, already visited upon numerous species in the Southeast, continues to loom for one third to one half of aquatic species here where we live.
The Chattanooga Zoo is doing its part to change that. The field research component of our Hellbender Project, for its first five seasons, focused on following up on historical and anecdotal records of Hellbenders in East Tennessee. It has mostly been a story of verifying the absence of Hellbenders in numerous streams, with a few happy exceptions. This season we were awarded the Cryptobranchid Interest Group Ron Goellner Conservation Fund Grant. It helps fund our study of eight Cumberland Plateau streams over the next year. What we want to determine is: 1) Do these streams still contain Hellbenders? 2) If they don’t, could they support the species?
Habitat structure makes Cumberland Plateau streams very hard to survey for Hellbenders. So, this season, in addition to traditional methods, we will be using a newer survey method that has been utilized and refined over the last several years.
Environmental DNA (or eDNA) is an amazing technology that allows us to pump a liter of water through a paper filter, and send it off to be tested for Hellbender DNA. It is proving a very useful tool to researchers by detecting bits of DNA in the water column from shed skins and fecal material. We can literally determine the presence of the species without seeing it. Several states have undertaken Hellbender reintroduction projects, but right now, there are no formal plans at the Tennessee Wildlife Resources Agency for reintroduction of Hellbenders in different locations—but down the road, there almost certainly will be, and we want to be ready.
The Chattanooga Zoo’s Hellbender Project also has a husbandry component. We have constructed a 40-foot-long, indoor stream with the goal of breeding Eastern Hellbenders in captivity. The St. Louis Zoo bred the Ozark subspecies for the first time in 2011, and the Nashville Zoo has bred Eastern Hellbenders with assisted reproductive technology. An unassisted breeding at the Chattanooga Zoo would be a first for Eastern Hellbenders.
We have two local conservation partners for the Chattanooga Zoo’s Hellbender Project, Terminal Brewhouse and Mohawk Canoes. Steve at the Terminal has crafted a fine seasonal beer they have dubbed “Hellbender Hefeweizen”, which is on tap now. Ten percent of sales go directly to support our field research efforts. They have also made Hellbender Hefeweizen shirts again this season. This is the third year of our partnership with the Terminal. Greg and Richard at Mohawk Canoes have been essential in providing gear when we need it in the field, and supporting the educational component of our Hellbender Project. Our conservation outreach focuses on the paddling and outdoor rec community. If a stream is good for paddling and trout fishing, it is typically good for Hellbenders.
Our economy is better when our biodiversity is protected. How we treat the rich ecosystems we have here, is ultimately how we treat ourselves and our children. We share habitat with these ancient giants. We are part of the ecology, not separate from it.
And we owe it to the system and ourselves to protect and reclaim it.