A spring peeper showing expanded air sac while singing. Photo: iNaturalist
By Kevin McKeon, Maine Master Naturalist
Climate change, habitat loss, and collections for the pet trade put many of our critters at risk, none more so than our amphibians. Spring peepers, however, are considered relatively secure within their habitats, and Maine’s rural landscapes hold valuable wetlands needed for these harbingers of spring. On April 8, 2025, the spring peeper, Pseudacris crucifer, became Maine’s official state amphibian. This recognition was bestowed in an effort to raise awareness of this species’, and many other amphibians’, delicate grasp on survival and the need for wetland conservation.
As temperatures warm during an advancing spring, we’ll be hearing the males announce their yearly arrival as they crawl from their winter hibernacula under logs, leaves, and soft mud to meet with mating partners at their natal vernal pools. Spring peepers are considered an indicator species, in that their presence denotes a healthy habitat. These rather delicate creatures are sensitive to environmental pollutants: Their skin absorbs lawn and agricultural chemicals we use, as well as the dirty air we create; and wild temperature swings caused by our changing climate add to their stresses. So, hearing them sing relates to a happy place for them, and indicates a healthy environment for us all.
This early spring awakening and migration happens during a warm, rainy night called “Big Night.” It’s often the first such night of spring, when amphibians area-wide migrate from their wintering grounds in the uplands to nearby wetlands and vernal pools to meet, mate, and begin their foraging activities. These evening hordes of travelers are one of nature’s great scenes for those who brave the dark, wet hours to witness this marvel. Recently, such conditions have existed, and great amphibian movements have been noted. The Maine Big Night Project organizes volunteers to assist in safely helping animals cross roads in amphibian-rich areas; they also collect and share data, providing valuable insight toward protection efforts. The Maine Department of Transportation recognizes that many accidents are caused by vehicle avoidance maneuvers at these amphibian crossings, so has collaborated with wildlife experts to engineer wildlife crossings for both human and critter safety under the Wildlife Crossings Project.
As the males emerge and begin singing, they tend to congregate, so their combined voices can reach farther into the night — and into the hearts of more potential mates. A single song has a volume of 90 dB, which can cause permanent hearing damage to humans after 30 minutes. A chorus of these 1-inch-long singers can reach two miles into the wetlands and forests. Some less vocal males will lurk among the stronger ones, waiting in ambush amidst the waters for their chance to pounce upon the wooed females. But she’ll select the loudest, fastest singer, so he’ll peep up to 4,000 times per hour for several hours, using up his fat reserves from the previous fall. Closing his nostrils, he forces air from his lungs through his vocal cords; the sound bounces off an expanded air sac almost half as big as his body, causing the resonating peep.
All this noise effectively advertises their presence to predators, and they do make tasty morsels for many critters. Hungry snakes and the other meat eaters of the fields and forests, awakening from their own winter sleeps, along with both overwintered and migrating birds, gather at woodland ponds, wetlands, and vernal pools for a protein feast. Fish, wading waterfowl, beetles, dragonfly larvae, and spiders feast on the eggs. So spring peepers and other amphibians, and their prolific egg-laying, are keystone prey species, offering a vital, early spring food source when little else is available. Valuable vernal pools are a food chain base for a landscape, so considerations have been enshrined in law for their protection.
But nature has provided a special tool for our peeper to help with its survival — exceptional camouflage. Its markings blend in with leaf litter, and a dynamic coloration gift allows chameleon-like skin color-changes to match its surroundings in about 45 minutes! Also, a mucus-like fluid is excreted between its toes that aids in climbing along just about any surface type, to access sheltered areas in their favorite habitats — trees. This wet toe fluid permits an adhesive quality useful in crawling over smooth or rough bark or rocks. They’ve been spotted on vinyl siding, complete with their matching skin coloration, and with brown skin on decks.
When it’s time to return to its winter hibernaculum, our frog’s glucose-rich blood surrenders this sugar to the frog’s cells, pumping the sugar solution into cells for making a cryoprotectant, a type of anti-freeze solution — as in the notable wood frog — mitigating freezing and dehydration damages. Covered with a layer of leaves, our peeper will undergo several freeze/thaw cycles during fluctuating winter temperatures, protected by its marvelous winter survival adaptation. It’s generally believed that spring peepers were one of the first amphibians to have migrated north during the retreat of the Laurentide Ice Sheet about 13,000 years ago.
So, for a backyard full of song, leave the leaves for our singing frogs to sleep under until they’ve serenaded us for a while; leaves house a plethora of other critters, too — many of which will feed our peepers and returning birds. And maybe consider a small backyard water garden; the amphibians will find it — along with dragonflies, whose water nymphs spend years in the water, eating mosquito nymphs, later to emerge and keep other biting pests at bay. Our own water feature has been visited by great blue herons on occasion, perching along the stone edge and among the nearby tree branches — looking for a peeper buffet!
Vernal Pools: https://sanfordspringvalenews.com/out-in-the-woods-23/
Maine Big Night Project: https://mainebignight.org/
Wildlife Crossing Project: https://www.maine.gov/dot/about/funding/grants/wcpp
Wood Frogs: https://sanfordspringvalenews.com/out-in-the-woods-24/
Send questions or ideas for this column to kpm@metrocast.net.
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