You’ve heard of horse whisperers. How about frog listeners?

The Department of Natural Resources is recruiting volunteers to use their ears to help survey the state’s frog and toad population. The survey, done each year since 1996, is part of a nationwide monitoring program.

The 200 or so Minnesotans who participate get a CD of frog and toad calls (not “Rainbow Connection”), a poster of the state’s 14 species, and other information. Volunteers take to routes around Minnesota to listen in and estimate the number and kinds of amphibians in a given area.

The DNR uses the data to understand how populations change and where species might be moving.

With a little practice, the average Minnesotan can distinguish among the species pretty easily, said Heidi Cyr, the DNR’s frog and toad volunteer survey coordinator.

“Once they get out there, they know what they’re listening to,” she said.

Volunteers will go out three evenings in all during the spring and summer, starting in mid-April. Each will travel one of about 250 routes and make 10 stops. Most metro-area routes are filled, the DNR says, but many are open in more rural areas.

“It’s not very technical,” said Cyr, “but it does give us a lot of information on what species are calling where.”