Don Lyman
The Boston Globe, March 25, 2022
A spring peeper in the Middlesex Fells clings to the finger of 11-year-old Eoin Dryden. The tiny brown frogs are hard to see. DON LYMAN
Standing waist-deep in a vernal pool at midnight, I don’t know which is colder, the 40-degree late March air, or the frigid water. My rubber chest waders keep me dry, but don’t provide much protection from the cold.
My friend and fellow biologist, Tim Beaulieu, who has a habit of dragging me out to vernal pools on cold, rainy spring nights to look for frogs and salamanders, is standing in the water about 20 feet away. Scanning the surface with his headlamp, he looks for spring peepers — inch-long treefrogs that congregate at vernal pools in the spring to breed.
The tiny brown frogs are hard to see, but their collective chorus is so loud, I have to shout for Tim to hear me. There must be hundreds of them calling from the partially submerged shrubs about 15 feet in front of us.
The scene I describe above was from 12 years ago, but the high-pitched whistling of spring peepers is a familiar sound across wooded landscapes throughout Massachusetts and the Northeast on spring evenings. And Tim is still dragging me out to vernal pools on cold, rainy spring nights.
Vernal pools are temporary ponds that form in the woods from snow melt and rain, and generally dry up by mid to late summer. These ephemeral wetlands attract not only spring peepers, but other amphibians such as wood frogs, gray treefrogs, and spotted salamanders, which also breed in the pools. And they are home to an array of invertebrates, including aquatic insects and their larvae, fairy shrimp, and fingernail clams.
A spring peeper in the Middlesex Fells clings to the finger of 11-year-old Eoin Dryden. The tiny brown frogs are hard to see. DON LYMAN
From a distance, peepers’ songs sound gentle and rhythmic, but when you stand near hundreds of them calling in unison, they’re deafening. It’s the males calling, trying to attract females to mate with them.
“A robust chorus of peepers can certainly number in the hundreds, but I’m always surprised at just how loud an individual frog is,” said Matt Burne, senior ecologist with BSC Group — a civil engineering company in Boston — and vice president of the Vernal Pool Association. “I think a small number of frogs can have a deceivingly large presence.”
Spring peepers begin their breeding activity very early in the spring, said Burne, and are among the first amphibians to begin breeding when the ice is melting in early to mid-March.
“They will be heard among the quacking wood frogs and provide the soundtrack to the spotted salamander dance,” said Burne.
Male spring peepers produce their characteristic call by inflating the vocal sac on their throat, which resembles a balloon when filled with air, according to an article in the Farmers’ Almanac. The peeping sound is produced as air exits the lungs and passes over the vocal cords and into the vocal sac.
While spring peepers use vernal pools for breeding, they are also found equally in marshes, swamps, rivers, and lake and pond habitats, according to Burne.
“Because peepers have such a quick breeding cycle and can use a wide variety of habitats, they have a much longer breeding season, and will be heard calling through the summer,” said Burne.
According to “A Field Guide to the Animals of Vernal Pools,” coauthored by Burne and Vernal Pool Association president Leo Kenney, female spring peepers may produce up to 800 eggs, which they deposit in small clusters or as single eggs attached to aquatic vegetation.
The male grasps onto the female’s back, then fertilizes the eggs externally as they are released. The eggs hatch in seven to 10 days, and the peeper tadpoles grow over the next five to eight weeks, then metamorphose and leave their aquatic environment as juvenile frogs.
Like most tadpoles, spring peepers are herbivores while they’re in their larval stage and will graze on leaf litter and consume the algae and fungi that grow on it, Burne explained. Once they metamorphose to their adult form, they’ll feed on animals such as small insects and worms.
And like other tadpoles and frogs, spring peepers face an array of predators themselves.
“Peeper tadpoles would be prime targets for a lot of the invertebrate predators in breeding sites — frogs and toads, snakes, birds such as heron, and other species that hunt in water,” said Burne. “Adult frogs would certainly be preyed upon by larger frogs, snakes, mammals, and birds that might be able to catch them in terrestrial settings.”
Spring peepers are found in woodland areas across Massachusetts and New England, and from southern Canada to Florida, and throughout the South and Midwest.
Spring peepers are typically a beige or brown color, with a darker X-shaped pattern on their backs.
After breeding, spring peepers disperse back into the surrounding woodlands, according to the “Adirondacks Forever Wild” webpage. They spend the winter in forested areas, often near wetlands, where they shelter under leaf litter, logs, bark, moss, or shallow soil. They survive freezing temperatures by producing their own “antifreeze” by converting glycogen from their liver to glucose, which is dispersed throughout their bodies, where it inhibits the formation of ice crystals.
According to the National Wildlife Federation’s web page on spring peepers, the tiny frogs have a relatively short life span, only three or four years.
This year, on a cold, rainy day in mid-March, the phone rings. An hour later I meet Tim and his young son, Finn, and our friend, Mike Miller, and Mike’s young son, Luca, at a vernal pool in the Middlesex Fells to look for frogs and salamanders. And the spring peepers are calling right on schedule.
Biologist Tim Beaulieu searches for frogs and salamanders in a vernal pool in the Middlesex Fells Reservation in Stoneham. DON LYMAN
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