Hellbender salamanders used to be common in streams across Kentucky, but their numbers have been on the decline in recent years. A recent study conducted by researchers at the University of Kentucky tested a new way of detecting these amphibians to try and pinpoint exactly where in the commonwealth they can still be found.
The sampling method tested in the new study involves collecting environmental DNA – also known as eDNA – to detect trace amounts of genetic material from the hellbenders along streambeds.
Sarah Tomke was the project’s lead researcher. She said the idea to test this new detection method on hellbenders was prompted and supported by the Kentucky Department of Fish & Wildlife Resources due to a lack of information about the species.
“We really haven't known very much about hellbenders at all. We don't know their distribution. We don't know how successful their populations are… what their demographics are,” Tomke said. “So they wanted to initiate this research project using environmental DNA to kind of do an overall sampling across the state to try and narrow in on where they are, so that we can then go in and find these populations and do more thorough research on them.”
Courtney Hayes is a wildlife biologist with Kentucky’s fish and wildlife department. She said eDNA sampling cuts down on physical labor and time that comes with traditional detection methods such as snorkeling surveys.
“eDNA really helps us prioritize where to start doing that, because Kentucky has so many streams. We have so many stream miles, so it's a lot for us to try to look at every single one of them and see if hellbenders are in there,” Hayes said.
In addition to reducing the burdens placed on the biologists, it can also reduce accidental habitat disruption caused by snorkeling.
According to the state fish and wildlife agency, eastern hellbenders found in the commonwealth are extremely sensitive to habitat disruption because they breathe through their skin and thrive under rocks. This means water pollution, rock removal or general sediment disruption can all have major impacts on the survival of these amphibians. KDFWR says factors like sand and gravel mining, dam constructions and water runoff pollution appear to be contributing to the species’ decline in population — which is now bordering on endangered status.
Hayes said in some rare instances while conducting snorkeling surveys, biologists have to lift rocks to find the salamanders, which can be detrimental to their habitat if it’s not done carefully.
Tomke added that snorkeling is not optimal for large-scale surveys, particularly when it comes to Kentucky’s large bodies of water – which make physically searching for the amphibians a challenge.
“It's extremely difficult to sample large rivers in general, certainly with traditional methods like snorkeling, you really can't do it. It's impossible,” Tomke said.
“But eDNA is also tricky too, because just capturing that tiny little DNA fragment within that enormous body of water, the chances of that are very small.”
Tomke’s team surveyed 90 sites along roughly 70 streams in Kentucky, including locations that have been historically known to have hellbenders as well as those that have optimal conditions for them. Of these tested locations, the team only found hellbender eDNA at a little over 20 sites.
Tomke attributes this result in data to sediment disruption, which she said affected the collection of eDNA and possibly the presence of the salamanders at those sites in general.
“It affects both… which makes it quite difficult, and it is a little challenging to discern. ‘Well, are we not detecting the DNA, or are they just not even here?’ And that is a very difficult question. There's no clear way to resolve that,” Tomke said.
Hayes said KDFWR is working to aid the declining salamanders through captive breeding programs and habitat management. She also said the agency needs more information about the whereabouts of these amphibians, and urged anyone who sees a hellbender in the wild to contact KDFW’s information center.
