The celebrated singing frog of Mason County

SPRINGFIELD — The squeaky-wheel call of the Illinois chorus frog starts just after sunset. On a still night, it can be heard up to a mile away.

It's not the only frog that can be heard in central Illinois, and it's far from the most common. There's also the staccato call of the tiny western chorus frog, which sounds like a finger being run across the teeth of a comb. American toads are out now, and their trilling call can even be heard in town.

But in the sandy areas of Mason County, about 45 minutes north of Springfield, the sound of the Illinois chorus frog is of particular interest to researchers.

The Illinois chorus frog is rare, occurring only in a few sandy areas of the state where conditions are just right for its survival.

But for the past few years, wet spring conditions have been a boon to the frogs and the people trying to find and study them.

Bob Bluett of the Illinois Department of Natural Resources is coordinating a team of field researchers, computer-mapping specialists and others who are trying to develop a statistically sound way to monitor populations of the Illinois chorus frog a threatened species in Illinois.

"It's really a challenging species to work with," Bluett said. "They are only above ground for a few weeks, and the habitats they choose to live in are here today, gone tomorrow due to weather, ground water and other variables."

For the past few years, field researchers who refer to their survey work as the "frog rodeo" -- have pulled lots of all-nighters.

When conditions are right, it's not difficult for the trained ear to identify an Illinois chorus frog without seeing it. It's similar to bird watchers who learn the calls and can tell which birds are around without ever raising their binoculars.

But Bluett says he wants to know more about why the frogs are there or not.

That's why they have been identifying likely habitats using computer models and sophisticated mapping software.

In dry years, the frogs may not be around at all. Then in wet years, the chorus can be deafening.

In addition to finding the frogs and their habitat, landowners are being contacted to enroll their wetlands in conservation programs so they can be protected.

Wetlands smaller than an acre and large as 25 acres have been protected so far this year.

Lots of questions remain.

No one knows for sure what the Illinois chorus frog does in dry years, and for that matter what it does after the breeding season in years of ample moisture.

But by finding the frogs and protecting their habitats, researchers hope to someday remove the Illinois chorus frog from the threatened species list and as a result, keep Illinois' spring symphony of sound in tune and with all of its players intact.