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March of the Salamanders: Migration Studied at Tennessee Aquarium

Spotted Salamander on moss 2

Each spring, thousands of Salamanders migrate within Tennessee’s woodlands, and biologists at the Tennessee Aquarium Conservation Institute are studying their movements as part of an effort to better understand the animals.

Like their cousins the Frogs and Toads, Salamanders are Amphibians. Most Salamanders hatch from eggs laid in water and become aquatic larvae known as tadpoles. The tadpoles metamorphose into adults that live in warm, moist places on land.

Tub of Spotted Salamanders
Tub of Spotted SalamandersPhoto Credit: Casey Phillips/Tennessee Aquarium

Why study Salamanders? Dr. Josh Ennen, a conservation biologist at the Tennessee Aquarium Conservation Institute, says that because of their sensitivity to environmental changes, scientists consider Salamanders and other Amphibians to be a kind of living bellwether for the health of the surrounding habitat.

“They’re almost like a canary in a coal mine,” Ennen said. “They’re a kind of indicator species that reflect the health of their ecosystem as a whole.”

The spring migration occurs when the adults return to the same pond they hatched in.  There, they mate and lay their own eggs. The Salamanders don’t travel far – maybe a few hundred feet – but getting to water is essential. If not laid in water, the jelly-covered eggs could dry out and die.

Salamanders migrate to vernal pools – small bodies of water that fill with winter and spring rains. These ephemeral ponds may only last a few weeks or months before drying out, but they last long enough for Amphibians to complete their life cycles. Vernal pools’ temporary nature means fish can’t live in them – and that’s important because fish would eat the Amphibians’ eggs.

Dr. Emmen and his colleagues collected, tagged, and released hundreds of Spotted and Mole Salamanders in just one day of their study. He notes that Salamanders migrate to the same pools for generation after generation.

Learn more and see additional photos below.

Salamander under blacklight
Salamander under blacklight
Salamander under blacklight

“Through these mass migrations, [Salamanders] bring a lot of nutrition from the terrestrial environment into aquatic systems that other animals can use in the food chain,” Ennen said.

“Some of the density estimates of Salamanders from the terrestrial and aquatic ecosystems show that they make up the greatest percentage of vertebrate biomass,” Ennen said. “Pound for pound, there are more Salamanders in these ecosystems than any other vertebrate.”

In the future, this research will help scientists to understand how larval Salamanders use vernal pools, improve the effectiveness of collection methods and help researchers to more accurately estimate Salamander abundance in a given location.

Even as scientists seek to better understand Salamanders’ migrations, seeing thousands of Amphibians making their annual journey, often right through backyards and neighborhoods, is a memorable experience more poeple — especially children — should experience, Ennen said. 

“I think people would be impressed by this behavior,” he said. “I always enjoyed knowing things are in my backyard. My kids do, too. I think it’s just a point of pride when you have anything that’s wild sharing the same space as you.”