It takes a particular sort of person to slog through a muddy forest after sunset, stand quietly in wading boots and long underwear and listen for the love songs of frogs.
The amphibians peep, they grunt, and, yes, they croak during mating season. Western chorus frogs make a sound like a finger stroking the teeth of a comb and are among the first to herald the arrival of spring in Chicago.
People like Nicky Strahl are there to record it. Her job: identify the whereabouts of some of the 13 species known to northern Illinois and report her findings to the Chicago Wilderness Calling Frog Survey.
"If it's kind of crappy weather, when humans don't want to go out, that's probably when you want to go out," said Strahl, 29, one of dozens of volunteers who take to the woods from late March through early July. "The longer we can stick at this, the better. We need consistency."
Conservationists worldwide declared 2008 the Year of the Frog to boost awareness of the rapidly declining populations, a trend that worries scientists who liken it to the extinction of dinosaurs. For a decade, scientists have sounded the alarm over a disease caused by the chytrid fungus, which they blame for wiping out entire populations of amphibians worldwide. Illinois scientists are gearing up this spring for further study of the fungus and its effect in the state.
Meanwhile, volunteers like Strahl and her southwestern suburban counterpart, Diana Krug, are on the front lines of a national effort to track which frogs are flourishing or disappearing. During this Year of the Frog -- and a leap year, no less -- they will traipse through swamps in the six-county Chicago area and northwestern Indiana in a massive effort to track amphibians' whereabouts and gauge the health of the environment.
"We're going back year after year because we want to see if the populations are changing," said Krug, who removes invasive plants for the Forest Preserve District of Cook County by day. "We're also trying to find out where the frogs are not doing as well so the land managers can identify those areas for restoration."
As a designated frog monitor and steward of Wright Woods, Strahl brings with her a backpack containing a global positioning device, flashlight, whistle, tape recorder and forms to fill out. She also trains new volunteers, describing the intricacies of the frog world to a hardy few who braved a February snowstorm for orientation.
"If anyone hears a wood frog, call me," said Strahl, who handed out CDs with the sounds of frog calls. "They only call one or two days a year. They just call their little bloody hearts out, and then they're done for the rest of the year."
The volunteers are important not only for their data-gathering but also as amphibian advocates, experts say.
Midwest environmentalists started tracking frogs in 2000 to record the distribution of the frogs and trends that might indicate a change in the ecosystem. With their permeable skin and a life cycle that includes both water and land habitats, the amphibians could serve as a warning system for a toxic environment, akin to the proverbial canary in the coal mine, said Michael Redmer, a herpetologist and habitat restoration coordinator with the U.S. Fish and Wildlife Service.
He is working with a researcher at Southern Illinois University on a statewide survey to determine the presence of the chytrid fungus. The researcher, Karen Lips, was among the first to report on the fungus in 1998.
"It's wiping out entire communities," said Redmer, who will spend the summer swabbing frog bellies as part of the survey. "We're going to see if that is widespread in Illinois."
Before researchers discovered the chytrid fungus, biologists noted the disappearance of more than 120 amphibian species since 1980 because of other factors.
"Frogs are the perfect little protein gumdrop in any wetland," Redmer said. "They eat a lot of small insects. But if you think of the number of other animals that eat frogs, you find predatory fish, herons, egrets and cranes. All varieties of snakes eat frogs. Raccoons eat frogs. That's a real pivotal place to be on the food chain."
He credits the frog monitors with alerting environmentalists to the disappearance -- and apparent reemergence -- of cricket frogs in northern Illinois. Within the last few years, the monitors have discovered cricket frogs despite prior reports that they had vanished from the Midwest.
"There's nowhere near enough professional biologists to collect that data," Redmer said. "The volunteers are contributing a huge amount of their time to this."
For truly dedicated frog fanatics like Krug, every spring marks the Year of the Frog. She outfits her flashlight with a red filter so she doesn't scare the critters that she comes across, with hopes of spotting a frog, as well as hearing its call.
"There are occasions when I will hear shuffling in the leaves," Krug said, "and behold, it will be an American toad sitting there."
She spends her days pulling invasive plants for the Palos Restoration Project in Cook County. She sometimes spots frogs and toads during the day, but it is easier to identify them at night when the birds pipe down.
"Every time you go out, it's always different. The wildlife doesn't sit still," she said. "There's birds or bats or fireflies. The fireflies are like fairy town, just blinking lights everywhere."
She treasures the spring peepers, which sounded tiny and fragile until the day she came across a slew of them in one pond. "It was deafening. You almost wanted to put your fingers in your ears."
Strahl showed similar dedication as she waded through a flooded Wright Woods recently, when the temperature barely cracked 46 degrees -- almost too cold for the frogs. She was joined by Ellen McKnight and her husband, Jeff Schumacher, also regular volunteers. They swapped stories about the time they annoyed a beaver or mistook the chattering of ducks for the call of an elusive wood frog until they reached their destination.
Standing silently, the hum of the tollway as background, they stood, heads cocked in the dark, listening. Finally, a trill in the distance, and McKnight pointed and nodded. The chorus frog.
Later, they agreed that the job of a frog monitor is not for everyone.
That is why butterfly monitors exist.