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Blog

Fatter Salamanders?

leah kirk

 Warning: Wrap your head in duct tape before reading the following

Chattanooga, Tenn. (March 14, 2017) – If thinking about the dangers of climate change has you missing sleep at night, consider the literal hot water that sensitive aquatic species may find themselves in if global temperatures continue to rise.

 When placed in artificially warmed water, some salamanders respond to the additional stress by — what else? — packing on the pounds.

 That’s the unexpected takeaway of a recent study by researchers from Sewanee: The University of the South, Southeast Missouri State University and the Tennessee Aquarium. The group’s findings soon will be published in Animal Conservation, a London-based, peer-reviewed scientific journal.

Normally, salamanders live in size-structured communities, meaning larger species tend to out-compete smaller species for prime position in the cooler, deeper waters in the middle of the stream. But research suggests smaller species will adapt more readily to the warmer conditions that climate change is predicted to bring about.

What will happen to the “bigger is better” power structure of salamander communities, the study investigators wondered, when streams warm to the levels predicted by climatologists? Would smaller salamander species begin to out-perform larger ones or would the status quo be maintained?

 Scientists tested this scenario by observing how warming the water in a temperature-controlled artificial stream bed impacted populations of Spotted Dusky Salamanders (Desmognathus conanti) and the smaller Cumberland Dusky Salamander (Desmognathus abditus), which is under review for listing as endangered by the U.S. Fish and Wildlife Service.

“What we found was that the smaller species actually didn’t grow longer, but they did increase their body weight,” says Dr. Josh Ennen, an aquatic conservation biologist at the Tennessee Aquarium Conservation Institute and one of the contributors to the study.

“Over a small amount of time, these salamanders shifted energy away from growth towards putting on weight,” Ennen adds, drawing a parallel to the paunch many people develop from over-eating during trying times. “If you’re stressed out, a lot of times, you put on more weight. In the wild, that’s a response where you pack on calories because you may need to burn those calories in the future.”

Whether stress was the root cause of the packed-on pounds — or ounces, in the case of such small amphibians — will require further research, but the result was definitely interesting and unexpected, Ennen says.

“In some animals, that’s a tell-tale sign that they’re in a stressful environment,” he says. “But we need to go further and look at things like lipid content and stress hormones to say, ‘OK, this was a stress response.’”

 This study comprises the first step in an ongoing research program Ennen and his partners are conducting to better understand the implications of climate change on salamander communities.

The Southeastern United States is one of the most salamander-rich regions in the world, with 80 percent of North America’s salamander species living within a 500-mile radius of Chattanooga, Tenn.

As “secondary consumers,” salamanders feed on plant-eaters like insects (primary consumers) and, in turn, are eaten by higher-level predators like fish, birds of prey and snakes. That makes them a vital link in the food chain of whatever environment in which they reside.

 Considering salamanders’ important ecological role and their proliferation in regional waterways, that makes understanding how they will be impacted by climate change all the more important, Ennen says.

 “You think about how many of them are found in our streams, and they become hugely important to the food web,” he says. “Collectively, the whole research program that we’re trying to build looks at how climate change affects headwater stream communities, which is an important conservation issue.”