Staff Writer

Some might call it the invasion of the amorous amphibians.

Marie Louise St. Onge, executive director of the Kennebunk Land Trust, said the quacking and peeping sounds emanating from ponds and vernal pools are a sure sign spring is here.

“I think it is magical – the opening of the opera and the antithesis of shoveling,” she said.

Male wood and tree frogs – commonly called “peepers” – are easy to hear but, at no longer than two inches, hard to see. 

This time of year, they have one thing in mind.

As days lengthen and nighttime temperatures creep above 40 degrees, wood and tree frogs emerge from hibernation and search for mates, said Susan Gallo, a wildlife biologist with Maine Audubon Society.

Gallo has spent a decade surveying vernal pools and freshwater ponds on the outskirts of Saco as part of a statewide effort to determine the health of amphibian species.

Taking a head count is not possible. Instead, volunteers listen and rate survey sites from one to three based on mating calls they hear, Gallo said.

Because yearly weather conditions affect how and when frogs emerge, more than 100 volunteers cover more than 60 routes comprised of at least 10 different sites. The sites are visited three times in the spring and early summer, Gallo said.

Gallo said ratings are shared with the national Audubon Society to help determine the condition of freshwater ponds and vernal pools, seasonal ponds that may evaporate before the summer solstice.

Suzanne Eder, the director of education at Wells National Estuarine Research Reserve, said frog mating calls can be heard a half-mile away. 

University of Maine at Orono Professor of Wildlife Ecology Malcolm Hunter said the calls, made as frequently as every two seconds, occur when air passes through frogs’ vocal sacs. Hunter said a good way to spot a peeper is to look for the vocal sac as it inflates like a balloon.

“A lot of people don’t realize these are frogs making the noise,” Hunter said. “They are remarkably easy to hear and remarkably hard to see.”

Vernal pools are favored as mating grounds for wood frogs because there are no fish to eat larvae, Hunter said.

When mating, the male frog is astride the female while she releases eggs into water.

Hunter could cite no data on the lifespan of tree frogs, but wood frogs can live three to five years, he said.

St. Onge said she has been hearing the calls of lovelorn frogs for a couple weeks now. As the spring thaw proceeds inland, shorelines around Sanford are coming alive too, said Gordon “Bud” Johnston, president of the Sanford – Springvale Mousam Way Land Trust.

“I have often thought of them as the heralds of the real spring. It means it is time to get the gardens ready,” Johnston said.

Johnston explained the difference in calls is literally one of day and night. The quacking sounds heard during the day are wood frogs. As dusk settles, tree frogs call with a sound resembling crickets.

As a boy growing up in Arlington, Mass., Johnston said he and his friends caught frogs emerging from the water. He said tree frogs are easier to see at night with a flashlight.

Catching them is not difficult, Johnston said. 

“Just scoop along the edge of a pond with a finely meshed net,” he said.

Hearing peepers can be as easy as opening a window or stepping into a yard. Johnston and St. Onge said trails maintained by their land trusts offer spots to see and hear peepers.

Johnston recommends the trail created on the former Sanford and Eastern Railroad running from Main Street in Springvale past Deering Pond to Hanson’s Ridge Road because of a vernal pool opposite the pond.

St. Onge said she has never seen a peeper.

“I am delighted to allow them their privacy,” she said. 

Staff writer David Harry can be reached at 282-4337, ext. 241.