FALMOUTH — The first frogs of spring have begun calling in southern and coastal Maine. And the rest of Maine is not far behind.

Vernal pools in the warmest areas of the state were hopping, literally, with wood frogs. These harbingers of spring make an unusual duck-like “quack” to attract their mates. And they make these distinctive calls for less than two weeks every spring.

“Wood frogs are the earliest frogs to emerge from the frozen mud,” said Susan Gallo, a wildlife biologist with Maine Audubon and coordinator of the Maine Amphibian Monitoring Project, which this year enters its 15th year of surveying Maine’s amphibian populations.

The project’s annual spring and early-summer surveys team-up volunteers across Maine to document the sounds and locations of different frog species. Their collected data helps biologists assess the status of amphibian populations, not only across Maine but nationwide as part of an effort coordinated by the U.S. Geological Survey. MAMP was launched in 1997 by Maine Audubon and the Maine Department of Inland Fisheries and Wildlife.

The program needs “citizen-science” volunteers to conduct two-hour roadside surveys three times throughout the spring and early summer. Ideally, volunteers have e-mail and Internet access and can commit to the project for more than one season. After listening to frog calls online, and passing a quiz on identifying the sounds of different frogs found in Maine, they conduct surveys first in early spring to hear spring peepers and wood frogs, then in late spring to hear American toads and northern leopard and pickerel frogs, and finally in early summer for gray tree, green, mink and bullfrogs.

Though most areas are in northern Maine, volunteers are needed in the Western Maine towns of Casco, West Paris and Bethel.

Volunteers make 10 stops along their routes, waiting five minutes at each and listening for frog calling activity. Since usually only one of Maine’s nine kinds of frogs is heard at any one time, it’s relatively easy for even first-time volunteers to identify which frogs they hear.

Potential volunteers should visit www.maineaudubon.org/conserve/citsci/mamp.shtml for more information, then contact Susan Gallo at 781-2330, ext. 216, or sgallo@maineaudubon.org.

Potential volunteers as well as the public are welcome to take the quiz on frog calls, designed by the U.S. Geological Survey, at www.pwrc.usgs.gov/frogquiz.