Wildlife Watch: The secret life of vernal pools

Published: Apr. 27, 2021 at 6:37 PM EDT
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HINESBURG, Vt. (WCAX) - When the snow melts in the spring, thousands of vernal pools form around the state become nurseries for amphibian life.

Wading through water, Vermont Fish & Wildlife’s zoologist Mark Ferguson is exploring a vernal pool for salamander and wood frog eggs. “A vernal pool probably to most people looks like a small puddle in the woods -- not very deep, maybe as much as two feet deep in most cases. If you come to one that’s a natural pool, it’s probably been there for a really long time, potentially formed by the glaciers. Because it’s so old, it’s formed a very special ecology and is able to support some species that really depend on that kind of habitat to survive,” Ferguson said.

This happens every year when pools fill up from snowmelt or spring rains. The pools provide several months of habitat for aquatic life to thrive before they dry out later in the summer. “When that happens, the weather starts to warm, then it will start to attract some amphibians,” Ferguson said.

The pools of water, specifically, attract mole salamanders and wood frogs, as well as help keep a healthy ecosystem flowing. “They will come in in the spring, they will all move down from their terrestrial habitats, they will have just a short time in the pool where they lay their eggs,” Ferguson said. “They lay their eggs, then they are back into the woods again, so when people see these animals they usually associate them with the pool itself, but really that’s just part of their habitat. The surrounding area is also very important to them.”

In this pool, eggs have hatched and tadpoles can be seen swimming around. Ferguson says its instinctive that the critters come back to the pools every year. “When the young are hatched and they leave the pool late in the summer they will head off in the woods. Some might travel to other areas and find another pool, but once they start returning to a pool to breed as adults, they tend to hone in on it every year -- that pool will be specific to them -- and they won’t go anywhere else,” he said.

Reporter Ike Bendavid: People walking in the woods, how will they tell the difference between a puddle and vernal pool?

Mark Ferguson: It’s hard to know just looking at one. It’s really the ecology that defines it as a vernal pool. It’s attracting or harboring certain species that depend on it -- that’s what we call a vernal pool.

And to help find or report a pool, the state has partnered with the Vermont Center for Ecostudies to document where vernal pools are found with, a list of just under 5,000 in the state. “So if they find a vernal pool, they can go online and register as a user on that site and report what they see,” Ferguson said.

He says depending on the site, the pools might last anywhere from three to five months to 5 months. And so far, this has been a dry year. “Oftentimes in conditions like this, we will see egg masses that are left up out of the water as the water drops and those eggs won’t survive. But those amphibians will be back next year -- the adults will be back,” Ferguson said.

Small pools that play a large role in the greater ecosystem.

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