The Eastern hellbender (Cryptobranchus a. alleganiensis) isn’t nearly as fearsome as its name implies. They’re actually somewhat cute, if you can get past the salamander’s slimy, mucousy skin that’s earned it such nicknames, such as “snot otter” and “lasagna lizard.”
Although hellbenders can grow up to two feet long, the amphibians are notoriously elusive and prefer to reside under large, flat rocks in well-oxygenated waterways that snake through Appalachia and the Ohio River basin. They are also increasingly difficult to spot, because their numbers are declining due to ecological issues. Based on a recent environmental study encompassing 90 sites across 73 rivers, researchers at the University of Kentucky now believe that they have identified one of the hellraiser’s main problems. They are losing their habitats to increasingly murky, sediment-filled waters, according to a study published in the journal Freshwater Biology.
Study co-author and biologist Steven Price said that it’s pretty difficult to nab a hellbender even if you aren’t conducting a United States Department of Natural Resources-funded survey.Â
“They live under big rocks. Lifting those safely takes time, people and care,” he said in an accompanying statement from the university. “When you see one in the wild in Kentucky, it’s special.”
Rather than spend untold hours wading through rivers in the hopes of spotting their hellbenders, Tomke, Price, and their colleagues instead relied on trace evidence from living organisms known as environmental DNA (eDNA). After collecting and filtering river water, the team tested the samples for a gene only seen in this species. This allowed them to avoid wasting time by shifting the massive stones or snorkeling for salamanders. The biologists ultimately detected hellbender DNA at 22 locations across Kentucky, 12 of which had existing historical records related to the animals. Next, they used a statistical occupancy framework to determine where hellbenders live, and when their eDNA is easiest to pinpoint.
“We could clearly tie stream habitat quality to where hellbender DNA turns up,” added study co-author Sarah Tomke. “It brought the science together and showed what managers can do on the ground.”
The team determined that the amphibian’s local habitat was a larger factor in where it lives than overall water chemistry or land cover. Larger streams lined with greater amounts of gravel, cobble, and bedrock correlated to more hellbenders. However, their numbers declined where grain and silt started blocking the crevices underneath rocks.
“Fine sediment is a big problem,” explained Tomke. “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.”
They also discovered what time of year is best to sample for hellbenders. Early fall, especially during September’s breeding period, appears to be the most sensible time. The creatures shed extra genetic material in early fall, making them easier to detect.
Beyond their uniqueness, the study’s authors add that hellbenders can act as excellent bellweathers for an ecosystem’s health. When their populations diminish, it frequently hurts other species who prey on the amphibians.
“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.”
Thankfully, it sounds like the most extensive hellbender mapping effort of its kind wasn’t a total bust for its participants.
“Seeing a hellbender is incredible, and holding one is next level,” Tomke said.
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