Even with little stumpy legs, these salamanders are made for extreme walking up to 9 miles

The hit mobile app of the summer, Pokémon Go, encouraged players to take an average of 955 extra steps daily — at least for the first week of hunting virtual beasts. So found a recent study in the British Medical Journal. To the smallmouth mole salamander, a true pocket-size monster from Ohio with long-distance urges and wee limbs, an extra thousand steps in a day? Peanuts.

Like eager Pokémon Go fans, the salamanders are on the lookout for other creatures, too. The amphibian motivation is not collection but companionship, however, or at least getting to know each other in the biblical sense: A drive to sexually reproduce, determined biologists from Ohio State University and Eastern Michigan University, propels the mole salamanders on stump-legged journeys of up to nine miles at a go.

Study author Robert Denton, an Ohio State University ecologist and graduate student, likened the traveling salamanders to endurance athletes. “Some of them could walk for two-plus hours straight without tiring themselves,” he said in a news release. “That’s like a person lightly jogging for 75 miles before wearing out.” (If you have not lightly jogged 75 miles recently, this would get you from Washington to downtown Baltimore, and just about back again.)

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The researchers had salamanders walk upon a custom treadmill until the animals were fatigued. The animals were allowed a brief pause every three minutes, in which the researchers would wet the creature’s skin and check for fatigue, Denton told Gizmodo; a salamander that could not flip itself over when placed on its back was considered too tuckered out to continue.

As the scientists wrote recently in the journal Functional Ecology, the average sexually reproducing salamander could walk six miles on the treadmill. A few made it even farther.

The researchers compared the smallmouth salamander to a related species, which was different in one key aspect: All of the comparison animals were female clones, a type of Ambystoma salamander that does not need to mate. Instead, these unisex amphibians steal genetic material from salamanders of different species. As National Geographic put it in May, “Instead of using that DNA to fertilize their eggs, the all-lady salamanders simply add it to their own genomes.”

Lady clones, though, could not walk as far. They became fatigued after traveling only about a quarter of the distance of the smallmouth salamanders. One possible explanation was that the lack of breeding weakened the animals’ endurance. “Essentially, not mixing up your genomic material often enough likely causes some problems for genes that you need to make energy,” Denton said.

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The need to breed translated to the wild: Denton and his colleagues collected genetic data from salamanders in distant wetlands. The DNA analysis, taken from 445 samples of salamander tails in Ohio, indicated that the sexually reproducing salamanders traveled twice as far from their birth wetlands than the clones did. (Actually following a salamander on a journey through the Buckeye State was deemed too impractical, and salamander skin was too sensitive to attach a radio or other sort of tracker.)

Studying breeding habits of amphibians are more than an excuse to put a salamander on a tiny treadmill. As a group, amphibians — which includes salamanders as well as newts and frogs — are some of the most threatened animals on Earth, with approximately one in three species declining. In the United States, frogs like the western toad are vulnerable to a disease brought about by a fungus called chytrid; in Europe, a form of chytrid has also ravaged the local salamander populations.

During their long hauls through Ohio, the salamanders face threats less exotic than killer fungi, too. They could get stuck in a place without access to water. “It has to be incredibly intimidating for these tiny salamanders,” Denton said. “They could get eaten by a crow or a raccoon.”

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