A peep into a frog affair

Posted March 08, 2013, at 11:55 a.m.

The sun sinks over a meadow and the chorus begins.

Spring peepers — tiny frogs with exceptionally big voices — wake after a long winter hibernating. And everyone know it. Their song, a mixture of high-pitched chirps, seems jubilant, as if announcing the arrival of warmer days. But what’s really going on? Why all the ruckus?

It’s actually a battle, an annual amphibian competition that takes place each spring in Maine wetlands.

The noisy competitors are the males. Each male stakes out a square foot territory (sizeable for an inch-long frog), and defends it with gusto from encroaching males. All the while, they sing for the only prize: a female frog to mate with.

“Even with that deafening chorus, you’re only hearing half the equation as far as the quantity of frogs,” pointed out Phillip deMaynadier, wildlife biologist for the Department of Inland Fisheries and Wildlife.

As the male peepers emit loud, high-pitched calls by expanding their throat pouch, the audience clings to grass and shrubbery by the discs on their toes, listening for strong singers.

“Some work suggests that females are being choosy with the males they select and breed with,” said deMaynadier. “In large part, the chorusing of the male says something about the fitness and size of the male.”

They’re actually taking a big risk by singing their hearts out, night and day, in the name of love. By doing so, the males announce their location not only to potential mates, but potential predators, such as snakes, raccoons and herons, said deMaynadier.

After a long and lonely winter hibernating under leaf litter, peepers shake off the deep sleep in late March or early April and keep on singing through May and as late as June.

“They go through several periods throughout winter when their bodies do actually freeze, and it’s somewhat of a mystery as to how they do this, though we’re starting to uncover it,” deMaynadier said. “Essentially, they have a mechanism for moving water out of their cells and reducing the freezing point of their body fluids by generating higher glucose levels in the winter.”

The peeper is of the tree frog family and the chorus frog genus, “Pseudacris,” which is derived from the Greek words “pseudes,” meaning false, and “akris,” meaning “locust.”

The peeper’s scientific name, “Pseudacris crucifer,” was chosen because “crucifer” in latin means “cross bearing,” and most peepers sport dorsal marks in the form a crooked “X” on their light brown back. This camouflage skin makes them incredibly difficult to spot in their natural habitat.

“It’s amazing. I don’t have much trouble finding too many other species, but spring peepers are tough,” said deMaynadier. “It’s paradoxical. You can hear their calls up to a quarter mile away, but you can be within 18 inches of a spring peeper, staring, and just not find it.”

He suggests searching for peepers at night with a flashlight, which will narrow your field of vision and help you focus on small areas. Also, deMaynadier has noticed that peepers seem less timid at night than they are during the day. At night, he can usually walk right up to them.

“I even put my hand out next to one and it voluntarily moved onto my hand and kept calling,” he said.

Peepers are abundant in Maine and the eastern half of the United States, but as a whole, frogs aren’t doing well worldwide, deMaynadier said.

“Amphibians as a group are experiencing a greater rate of decline in population and greater rate of extinction than any other invertebrate group in the world,” deMaynadier said.

There are several theories as to why this is happening. Amphibians require healthy terrestrial and aquatic ecosystems, said deMaynadier, and they aren’t mobile enough to migrate long distances if their habitat is destroyed. In addition, their permeable skin and eggs is susceptible to environmental stressors, such as pollutants, ultraviolet radiation and climate change.

“My only word of caution is, even though we hear spring peepers in our backyard marshes, and they sound abundant, we don’t really have a frame of reference to know how well they are doing in terms of past populations,” deMaynadier said.

So when a peeper calls out in the spring, luring a mate to his patch of soggy land, he’s ensuring that next year’s chorus remains strong, that when he dies at the ripe age of 3 years old, his offspring will carry on the tune that announces to Maine people, “Spring is here.”

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