The mysterious vanishing cricket frog

by Karol Crosbie

Survey validation for a declining amphibian, Blanchard’s cricket frog (Acris Crepitans Blanchardi) , in western Ohio
by James Witter, Toledo, Ohio

Is chytridiomycosis (Batrachochytrium Endrobatidis) present in declining populations of Blanchard’s cricket frog?
by Sheldon Steiner, Dalton, Ohio

Adviser for both studies, Richard Lehtinen, biology

It’s twilight at Killbuck Marsh in northeastern Ohio. The frogs’ symphony pulses and throbs. You can hear the gravelly grunt of the bullfrog; the loose-banjo-string song of the green frog; the fast, metallic trill of the gray tree frog. The musicians—entirely male— sing their mating songs with single-minded purpose.

But one voice is missing. The click, click-click, click-click-click-click of the tiny Blanchard’s cricket frog, once a staple of the chorus, has disappeared. Not only has he disappeared from central Ohio, he can no longer be found in formerly hospitable areas of Illinois, Indiana, Iowa, Michigan, and Wisconsin. Only small populations of the frog live in Minnesota and Nebraska, and they have entirely disappeared from Colorado, Ontario, South Dakota,West Virginia, and Arizona.

Other species of frogs are disappearing, too. There was a time when we understood the reasons for their departure. Humans developed a taste for the plump legs of one of the planet’s oldest species and ruthlessly harvested them. Records at the State Historical Society of Iowa reveal that a single frogger could deliver as many as four million frogs every season. In the 1900s, trains carried huge hauls of the delicacy to big city hotels.

Additional reasons for depletion are piling up: Loss of wetlands, pesticides, new predator game fish, acid rain, and agricultural and lawn care chemicals. Scientists estimate that nearly one-third of the more than 5,700 known amphibian species are now threatened with extinction.

But understanding eludes scientists who study the little cricket frog, including Rick Lehtinen, assistant professor of biology. Lehtinen and his students have studied the frog for the past four years, and his past research has ruled out acid rain as a reason for population declines. This year, two independent studies tackled the question.

Sheldon Steiner: What about the chytrid fungus?

The chytrid fungus was a good hypothesis, and one that had never before been researched in the cricket frog population. The fungus, which is found on at least four continents, is spreading fast, and is the suspected culprit behind the depletion of many frog species, says Lehtinen. Frogs, who breathe through their skin, asphyxiate when the fungus breaks down skin proteins.

Sheldon Steiner studied DNA from the toe samples of 201 Blanchard’s cricket frogs from five states. The scientific process, he discovered, was decidedly unglamorous. “I was glad to be done with the laboratory work,” he says. “It was tedious, repetitive, and not very fun.”

But his work paid off. He found that the fungus was present in the samples. That was the bad news. The good news was that apparently, it wasn’t causing declines. “Sheldon’s work was very good, because no one knew if the fungus was present in this species,” says Lehtinen. “Because Sheldon found it was present in frogs living in areas where populations aren’t declining, it suggests that the fungus probably isn’t directly involved in declines.”

Jim Witter: Can you hear me now?

Frog research involves a very low-tech process, beloved by children everywhere: Catching the frog. “You approach slowly and grab,” says Lehtinen. “I don’t do anything different than when I was six years old.” Researchers take a small clip from the frog’s toe and release the frog, which goes on to live a normal life.

But it’s an imperfect art. If you don’t hear a frog and you don’t see a frog, does that mean it’s not really there? Researchers seek ways to reduce “false zero” conclusions that are based on insufficient evidence. And that’s where the work of Jim Witter comes in. If the researcher plays sound recordings of male frogs, might that stimulate calling activity?

Spared from the tedium of the microscope,Witter conducted all of his research in the field, carrying his boom box loaded with a cricket frog’s song to 324 ponds, lakes, and streams in western Ohio. There were misadventures—the time an irate farmer came after the Wooster frog team with a gun; the time the group almost lost an expensive piece of equipment to a raging river; the time Witter stuck his professor’s car in the mud. But the answer to the question was conclusive: Recordings do not entice the little cricket frog to sing.

Witter also studied to see if naturally occurring variables might be predictors of cricket frog-calling activity. He found that humidity, moon phase, and the presence of bullfrogs were all significant predictors of cricket frog-calling.

Following graduation,Witter completed two internships in outdoor education at Pennsylvania State University and Antioch College in Yellow Springs, Ohio. He says he loves the work of the naturalist and hopes to pursue it. Steiner says he’ll take some time off and then hopes to go to graduate school in wildlife or conservation biology.