Will Ternes, an ectotherm keeper at the zoo, said exhibiting hellbenders can be problematic because their skin is photosensitive. Hellbenders like to live under large, flat rocks and the creatures react if any part of their body is exposed to sunlight. The new exhibit attempts to accommodate both the hellbenders’ desire to remain hidden and the visitors’ desire to view these seldom seen salamanders.
Ternes added that the natural homes of hellbenders are clean, well-oxygenated streams at mid-level elevations. Public lands are important to the survival of these creatures, which are threatened by habitat fragmentation.
The Chattanooga Zoo has taken an interest in hellbenders because conservation of biodiversity in this geographic region is important, according to zoo officials. Nearby Polk County, by the way, has the greatest population of hellbenders in the area.
Dams are perhaps the greatest ongoing threat to hellbenders. The structures, which created the vast number of reservoirs in the Southeast, change stream flow and temperature. Hellbenders prefer 58 – 60 degrees (F). Warmer reservoir water means less dissolved oxygen, and less chance for the hellbenders to survive. Hellbenders also prefer shallow water and can’t survive the deeper waters behind dams. The dams are also a barrier to dispersal and genetic diversity for long-term success.
Siltation from agriculture is another threat. It often pollutes streams and fills in den sites, which harms the survivability of hellbenders and their prey species. Stream bank restoration and good land-use policy encourages healthy streams and healthy hellbenders.
The Chattanooga Zoo joined with the United States Department of Agriculture in a regional conservation partnership for hellbenders. That effort was delayed due to COVID-19, but talks are resuming.
The eggs that hatched five years ago came from the Nashville Zoo at Grasmere. The Nashville Zoo collected them from the Duck River for restoration projects. The Chattanooga Zoo has resumed close communication with the Nashville Zoo as the hellbender project moves forward. Restoration started at the St. Louis Zoo, which is known as the gold standard for hellbender research and restoration.
The zoo also has an older group of hellbenders from Cherokee National Forest watersheds, which are 10 to 11 years old. They are still under 5 pounds and have yet to reach full length. Hellbenders are relatively long-lived species and individuals 30 years old or more are not unusual.
For long-term survival of the eastern hellbender, Ternes said the most important step is to maintain the epicenter populations at Mark Twain National Forest in Missouri (the only population to be listed for protection under the US Endangered Species Act), the Allegheny Mountain population, and the Cherokee National Forest population. He also suggests restoring the habitat in other, less mountainous areas.
The hellbender’s presence means a stream is healthy. They also keep populations of crayfish and other small species under control. Their bodies have not changed much in 150 million years, and hellbenders are the only North American species of large salamanders. He said that he has never seen any of the three Asian species of giant salamanders, much larger than the Hellbender. The Cincinnati zoo has an exhibit of the related giant Japanese salamander.