The key finding, published online this month in the journal Functional Ecology, was that not all the salamanders caught from the private land of property owners in Crawford county, Ohio were extreme athletes - only the versions that sexually reproduce.
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When tested, the all-female, asexual version of the same species reached their quitting points much sooner - after an average of about 1.5 miles. This version of the salamander, also found in Ohio fields, reproduces by cloning and sometimes snatching sperm left behind on nearby leaves and twigs.
The finding suggests that by striking out to (relatively) distant wetlands to find a mate, the sexual salamanders mix up their genes in ways that ultimately makes them stronger.
"Essentially, not mixing up your genomic material often enough likely causes some problems for genes that you need to make energy," Denton said in a press release.
Denton and his team cross-referenced genetic data collected from salamanders in a variety of Ohio wetlands with the distances the salamanders could walk on a treadmill. The findings showed those salamanders who were identified as genetic outliers in certain wetlands (and so who had apparently traveled far to arrive there), were also the kinds who were capable of walking long distances on treadmills.
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Putting salamanders on a treadmill is as tricky as it sounds.
The treadmill must of course be small, it also must be slow-moving and remain damp. It further requires side walls to keep the amphibians on track since salamanders don't tend to walk in straight lines.
Fortunately, the team was able to borrow a custom-made salamander treadmill from colleagues who had used it in previous research. The treadmill has plastic walls and a belt made of a wetsuit-like material that ensured the salamanders' feet stayed moist.
To get the salamanders started, a lab worker would tap or sometimes pinch the creature at its rear.
Once the salamander started walking, a lab worker (usually a graduate student) would then play assistant coach. Every three minutes the walking salamander would be doused in water and given an exhaustion test. The test was fairly simple: the salamander is turned over on its back.
"Once they're exhausted they don't turn back over," explained Denton. "They're done."
Watching the video of a salamander walking on a treadmill may make the research seem "cool," said Denton, but, in fact, he says it was "pretty mind-numbing" and required hours of tedious lab hours.
Denton hopes those lab hours will pay off in helping guide conservation efforts for salamanders and other animals. He points out that since two versions of the same species of salamander were shown to have very different habitat needs, it suggests there's rarely a one-size-fits-all solution when it comes to conservation.
"Our research shows how two very closely related animals can have very different abilities," he said. "So the best habitat management solution can't treat all animals - or even a single species - like a single unit."