UK studies where Kentucky’s hellbenders live and what they need to survive

A new University of Kentucky study used environmental DNA (eDNA) to search 90 sites across 73 rivers for Eastern hellbenders — large, secretive salamanders nicknamed “snot otters” and “lasagna lizards” for their mucous secretions and the skin folds that help them breathe.

Now, a UK Martin-Gatton College of Agriculture, Food and Environment (CAFE) study published in Freshwater Biology reveals a correlation between the presence of hellbenders and clean, rocky stream bottoms. Where fine sediment fills the spaces under rocks, hellbenders are far less likely to be found.

The project was led by Sarah Tomke, Ph.D., during her doctoral studies in the Department of Forestry and Natural Resources, working with department interim chair Steven Price, Ph.D. This work was supported by the McIntire-Stennis Cooperative Forestry Research Program of the United States Department of Agriculture (USDA) National Institute of Food and Agriculture (NIFA) along with funding from the Kentucky Department of Fish and Wildlife Resources.

Tomke and field crews collected water, filtered it and tested for a gene specific to the hellbender. This approach enables biologists to focus their searches without turning over heavy rocks or spend days snorkeling. The team detected hellbender DNA at 22 sites statewide, including 12 with historic records, then used a statistical “occupancy” framework to separate two questions: where are hellbenders present and when is their DNA easiest to detect?

“Seeing a hellbender is incredible, and holding one is next level,” Tomke said. “But my favorite part was the occupancy results. We could clearly tie stream habitat quality to where hellbender DNA turns up. It brought the science together and showed what managers can do on the ground.”

Hellbenders can reach two feet long. They hide under broad, flat rocks in cool, well-oxygenated rivers across the Ohio River basin and Appalachian region. They were once widespread in Kentucky but are now difficult to find.

“They’re especially hard to spot here,” Price said. “They live under big rocks. Lifting those safely takes time, people and care. When you see one in the wild in Kentucky, it’s special.”

The study found that local habitat mattered more than broad water chemistry or land cover. Hellbender occupancy rose with more cobble, gravel and bedrock in the streambed and with larger stream size; occupancy declined when fine sediment clogged the gaps under rocks. The researchers also found that higher total organic carbon in the water made eDNA harder to detect, a useful clue for planning eDNA surveys.

“Fine sediment is a big problem,” Tomke said. “It fills potential nest sites and the small spaces that larvae use for shelter. Without that space under rocks, animals can’t reproduce or survive for long.”

The team sampled across seasons and shows that early fall — especially September, during the breeding period — is a smart window for eDNA surveys. That’s when animals shed additional genetic material, making positive identification easier to pick up and follow-up searches more efficient.

While Tomke’s crew didn’t confirm new animals beyond a known, well-studied site during her Ph.D. study, the roadmap still proved effective: Kentucky Department of Fish and Wildlife biologists later found hellbenders at two eDNA-positive streams, verifying the method worked.

Price called the survey the “most extensive eDNA effort for hellbenders in Kentucky to date,” saying it fills a long-standing information gap.

“Sarah’s project gives us clear habitat targets,” Price said. “First, keep sediment out of streams. Then protect and rebuild rocky beds and forested streambanks. That’s how we give this species a chance.”

Hellbenders’ importance in the ecosystem

Hellbenders also act like an early warning system. When their populations decline, it often signals trouble for many other stream species who rely on the hellbender as food. For a creature that looks ancient — and truly is — the lesson is modern and local: clean water, intact habitat and intelligent monitoring can guide recovery.

“Residents, landowners and communities play a role in keeping soil out of streams and protecting habitat,” Price said. “Stabilizing eroding banks and road ditches, managing construction runoff, and implementing farm practices that retain soil in place can help reduce fine sediment. Replanting trees along streams helps cool water, anchor banks and filter runoff. In some areas, adding stable rock and rebuilding clean, connected streambed can restore the space under rocks that hellbenders need to nest and shelter.”

The study was also supported by the Society of Freshwater Science, Northern Kentucky Fly Fishers and the Kentucky Society of Natural History along with funding from the department, the Martin-Gatton CAFE Richards Graduate Student Research Activity Award, the Tracy Farmer Institute for Sustainability and the Environment’s Karri Casner Environmental Sciences Fellowship and the UK Appalachian Center Eller & Billings Student Research Award.

Tomke conducted the research at UK and is now with the University of Pennsylvania.

To learn more about the Department of Foresty and Natural Resources at Martin-Gatton CAFE, visit https://forestry.mgcafe.uky.edu.

This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, McIntire-Stennis Cooperative Forestry Research Program under award number KY009040. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the Department of Agriculture.