Vernal Pools
If you’re waiting for spring to really take hold before getting out to a wildlife sanctuary, you may be missing a spectacular natural occurrence—the annual vernal pool breeding season, with its accompanying symphony of frog and toad calls.
Vernal pools are temporary, isolated ponds that form when spring rain and meltwater from ice and snow flood into woodland hollows and low meadows. These pools provide critical breeding habitat for certain amphibian and invertebrate species—since vernal pools eventually dry up, they are inaccessible and inhospitable to predatory fish.
Warming spring days trigger amphibians like spotted salamanders and wood frogs to migrate to vernal pools to breed, often in great numbers, on the night of the first soaking rain above 45°F—a phenomenon known as “Big Night.”
What You Might Encounter
As you approach a vernal pool in early spring, you can hear a chorus of wood frogs “quacking” their breeding calls. Once you arrive at a pool, look closer and you may see tiny fairy shrimp. These crustaceans are remarkably hardy and resistant to drought and cold—their eggs can even survive being digested by animals.
Spotted salamanders may migrate up to a half mile to get to a vernal pool, where they gather in a group called a “congress” for mating. Perhaps the most well-known vernal pool denizen is the spring peeper, a type of tree frog. Although they are often less than an inch in size, their familiar sharp, peeping calls can carry for a quarter mile.
Protections
Many Mass Audubon sanctuaries have vernal pools, most of which are accessible to visitors (although a few are not). Several are certified by MassWildlife’s Natural Heritage & Endangered Species Program, a designation that provides the pools with important protections under state and federal laws.
Learn more about vernal pools, including how to protect them through state-level certification.
Sounds of a Vernal Pool
Listen to a chorus of wood frogs at Broadmoor Wildlife Sanctuary’s vernal pool viewing platform.
Where to See Vernal Pools
Here's a quick guide to vernal pools at our sanctuaries to help you get out and see what all the fuss is for yourself. As a general rule, once you hear the first peepers chirping in spring, it’s time to go in search of vernal pools.
You’ll find an easy-to-access vernal pool at the Museum of American Bird Art in Canton, where a five- to 10-minute walk from the parking lot will take you along the Main Loop Trail right up to the edge of the pool. Here you can find adult and juvenile wood frogs, spotted salamanders, and green frogs. You may even encounter wood ducks or spot a barred owl in the pine trees that surround the pool.
Oak Knoll in Attleboro has three vernal pools, as well as an amphibian cover-board array, all of which are monitored by interns from Bridgewater State University.
Just down the road at nearby Attleboro Springs, the universally accessible Reflection Trail leads to an observation platform looking out over the sanctuary’s vernal pool.
Wachusett Meadow in Princeton has a number of vernal pools. While most of the pools are off trail and inaccessible to visitors, there is a shallow vernal pool just visible from the Brown Hill Loop Trail near Otter Pond, as well as the Rock Fire Pond on the Pasture Trail.
At Broad Meadow Brook in Worcester, the Frog Pond and Holdredge trails have easy-to-visit vernal pools hosting wood frogs, spotted salamanders, and a variety of invertebrates. The Frog Pond Trail vernal pool is also on a universally accessible portion. Both pools have observation decks.
Allens Pond in Dartmouth has several vernal pools, including an easy-to-view one on the Boulder Loop Trail and another, more challenging one within the center of the Woodland Loop Trail. The latter hosts more than 200 spotted salamander egg masses each year and hundreds of wood frogs, as well as four-toed salamanders. The pool is difficult to access, so it’s best to visit during a staff-guided program (make sure to wear waterproof boots).
Stony Brook in Norfolk has two certified vernal pools, one of which is close enough to the trail that chorusing wood frogs can be heard each spring. They also host spotted salamanders and, most years, fairy shrimp, along with numerous other wildlife and plant species.
Drumlin Farm in Lincoln has several permanent ponds that were all dug by previous farmers. Without any inlets or outlets, they lack predatory fish and, as a result, may all have wood frogs and spotted salamanders in the spring. The Ice Pond, next to the main parking lot, is the easiest to find. For a longer adventure, walk out to Rock Island Pond, which usually has fairy shrimp in early April.
In Northampton and Easthampton, Arcadia has more than 30 vernal pools. The most prominent and easiest to visit is directly behind the visitor center and viewable from the boardwalk.
Out on the Cape, Long Pasture in Barnstable and Ashumet Holly in East Falmouth have restored more than a dozen vernal pools for the eastern spadefoot toad, the rarest anuran (the order that includes frogs and toads) in Massachusetts. Ashumet Holly’s seven restored vernal pools and one natural pool can be found along the Ashumet Farm Trail, the Wheeler Memorial Trail, and the Mystery Tree Trail. Long Pasture’s six restored vernal pools and two natural pools are along the Beck Family Trail.
Broadmoor in Natick has a vernal pool with a short dock extending into it, about a quarter mile from the nature center. Follow the Indian Brook Trail along the field edge and into the woods, where you’ll find the pool entrance on the right. The dock allows visitors to lie on their stomachs and look into the water. It also protects the pool edges from damage to the plants and soil by foot traffic. Spotted salamanders breed in the pool but are rarely seen.
Moose Hill in Sharon has a number of vernal pools on-site, including five that are certified. Don’t miss the Vernal Pool Loop Trail, which passes beside two of the sanctuary’s longest-monitored pools, where staff and volunteers have conducted egg-mass counts since 2004.
This article is was featured in the Spring 2018 issue of Explore, Mass Audubon's quarterly member newsletter.