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Green Living

10 facts about vernal pools

At a training session, Vernal Pool Project volunteers learn to distinguish between the firm egg masses of spotted salamanders and the looser wood frog masses.          


Photo by Francie Von Mertens

At a training session, Vernal Pool Project volunteers learn to distinguish between the firm egg masses of spotted salamanders and the looser wood frog masses. Photo by Francie Von Mertens

The first and best reason you should care about vernal pools is you might not know what one is and it’s cool to learn new stuff. Vernal pools are formed by spring snowmelt and rains, and provide breeding grounds and habitat for several distinct species of amphibians and insects including wood frogs, spotted salamanders and fairy shrimp.

Vernal pools usually reach maximum water depth during the spring with “vernal” meaning of, relating to, or occurring in the spring, hence the name. Although they are temporary pools, undisturbed they occur in the same place year to year.

Vernal pools have two distinct characteristics which separate them from other types of wetlands. One, they do not permanently hold water and two, they are free of fish. Vernal pools dry up at some point each year or in some cases at least once every several years.

The lack of fish populations help the species that utilize the pools for breeding to survive. In this fish-free environment they can breed, lay eggs and the young have a better chance of developing without being eaten.

One of the unique species to vernal pools in our area is the spotted salamander. These creatures have up to a 20-year life span and may spend their entire lives living within hundreds of feet of the pool they were born in. Each season they will return to the same pool to breed, as will their offspring.

Although it’s relatively easy to find spotted salamander egg masses in a pool, the adults are very secretive and it’s unusual to spot one unless you catch them crossing a street during a rainy late-March or early-April night on their way back to their pool. It is not uncommon for the entire population of a pool to move across a street to their pool on the same night.

That quacking sound you hear on an early spring is the male wood frog breeding song (as opposed to the chirp of the peeper). Wood frogs are another one of the species used to help identify vernal pools. The identification is usually by their egg masses, which may contain up to 1,500 individual eggs from one female. Adult wood frogs spend very little of their lives in the pools, using them mainly for breeding.

Fairy shrimp are small (about an inch length on average) crustaceans that can be used to decisively define a vernal pool on their own. The female shrimp produce eggs in the pool which will only hatch after they have dried out with the pool and then been re-submerged, sometimes after several years of lying dormant. Because the eggs are drought and cold resistant they can be transported to other pools via the wind, on leaf litter on the feet of animals or even by ingestion by other animals.

Several New England states recognize the high value of these resources and actually have regulations in place to help protect them including Maine and Massachusetts. The EPA estimates that up to 90 percent of California’s vernal pools have been destroyed by development, threatening to extinguish these rare habitats forever.

Another good reason to care about vernal pools is because many of your neighbors do. For the past two springs several volunteers from the Peterborough area have been part of an initiative by the Peterborough Conservation Commission and Harris Center to identify vernal pools on town-owned land and conservation property. Volunteers include property owners interested in learning whether their land has vernal pools. If you’re interested please contact one of the members of the Peterborough Conservation Commission.

Matt Lundsted is a member of the Peterborough Conservation Commission.

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