Frog went a-courtin'and friends did count

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It's a warm evening in late March, and a group of trained volunteer naturalists clusters at a marsh inside the U.S. Fish & Wildlife Service's Patuxent Research Refuge in Beltsville.

They're here at the refuge's central tract, one of the Washington area's prime spots for frog-watching, to track the mating calls of the marsh's 12 species of frogs and toads. It's a census, in effect, and it's one way to learn whether the marsh's share of this order of animals, which is in worldwide decline, is holding its own.

The frogs don't care. It's spring, and they want mates, now. As the listeners take their posts, they hear what they've come to hear: Several high-pitched singers, all male spring peeper frogs no bigger than a human thumb, begin a melody.

Coming from somewhere behind the cattails to the left, the peepers' song swells to a chorus. Two listeners cup their ears to amplify and catch each nuance of the froggy reprise.

They soon pick up a rhythmic staccato bass line -- like the sound of several jolly old men chuckling -- interrupted by a series of alto trills from the trees on the distant side of the marsh, from toads keening with longing and passion.

The songs enthrall the three humans, too, as they return to their sport utility vehicle, borrowed from the U.S. Fish and Wildlife Service for the evening because its ruggedness suits the rutted roads of the refuge.

"I heard spring peepers, leopards and a few gray treefrogs," says Art Abrams of Greenbelt, 49, using the shorthand term for leopard frogs.

"Definitely," answers Lutz Rastaetter, another Greenbelt resident in his late 40s, "and it was almost a chorus."

The group members can barely see in the dim light of a new moon, so they turn on a car light to fill out their data sheets.

They note the species calling -- pickerel frogs and American toads as well as the peepers, leopards and gray treefrogs -- the approximate numbers calling (individuals, overlapping callers, or a chorus), the time, the exact temperature, wind levels and any background noises, such as passing cars, that may have interfered with the calls of the lust-filled frogs.