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Salamanders, tadpoles, whirligigs and more:Visiting a Vernal Pool

By Julie Reiff

This time of year, as snow melt and spring rains fill small depressions in the land, you are likely to come across pools in the forest or at the edge of a field.

Spotted salamander eggs at Intervale Gateway. Photo by Julie Reiff

These temporary spring or “vernal” pools have a wet-dry cycle that prevents permanent fish populations from living there. As such, they make an essential breeding habitat for certain species of wildlife, including salamanders and frogs. In Maine, species that need vernal pools in order to survive and reproduce include wood frogs, spotted and blue-spotted salamanders, and fairy shrimp. 

At a time when the northern woods can still seem in a winter sleep, these pools are very much alive. But how can we explore them without harming the creatures we want to see?

The first thing we can do is listen. Wood frogs make a distinctive quacking or turkey-like sound. Although wood frogs will only breed in vernal pools, other frog species may be found there, including the Gray Treefrog, American Bullfrog, Northern Green Frog, Northern Leopard Frog, Northern Pickerel Frog, and Spring Peeper. These other frogs are less picky and can breed in permanent ponds as well.

A green frog hides in the grasses at the edge of a vernal pool in May. Photo by Julie Reiff

Salamanders, though, do not make any sound. They call potential mates by pheromone signaling. You and I won’t be able to smell them, but we may find their eggs. Frogs and salamanders both leave large jelly-like masses of eggs. Wood frog eggs have a bumpy surface, and spotted salamander egg masses have another outer membrane holding the mass together and making it smoother. Those can be clear or cloudy. Don’t worry if they are covered in slimy green algae, as that can be a nutritious snack for some of the newly hatched amphibians! 

When visiting a vernal pool, try to disturb it as little as possible. There is so much life going on we cannot see—hiding under the leaf litter, hanging from submerged branches, or perfectly camouflaged. Be careful not to dislodge egg masses that may be attached to plants or twigs to help keep them away from predators. 

Spotted salamanders often return to the pools in which they were born in order to breed. This one emerged early during a warm spell in February last year. Photo by Julie Reiff

To see what might be living there, try taking a shallow white bucket or tray and carefully submerging it near the water’s edge. (Be careful; that water is cold!) Use a small hand lens if you have one, and be patient. In no time, things may start to wiggle. You may see dragonfly or mosquito larvae, whirligigs, or predaceous diving beetles. If you’re lucky you may see crayfish, tadpoles, or salamanders!

Concerns over mosquito-borne illness have driven many communities to eliminate standing water, but vernal pools, even though they host mosquito larvae, are home to so much more. Even those larvae are important food for the creatures that live there.

The loss of vernal pools leads to local loss of amphibian species, a decrease in biodiversity, and a decline in food available for many other animals that live in these areas. Significant vernal pools are protected in Maine. A pool is considered significant if it has fairy shrimp, a large number of wood frog, spotted salamander, or blue-spotted salamander eggs, or the presence of a state-listed endangered or threatened species like a spotted turtle or a ribbon snake. 

Join us for a webinar on April 11 with Maine Master Naturalist Bryce Hach, who will provide helpful content on one of the most unique ecosystems in Maine.

Meanwhile, I’ll be keeping an eye out for activity at a few vernal pools in Bethel and plan to offer a guided walk when conditions allow. Why not keep an eye out on the pools in your neck of the woods, or listen for the peepers? They’ll be calling before you know it.


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