After more than half a century, an endangered frog is back in western Wisconsin.

The state Department of Natural Resources this summer recorded the distinct call of the Blanchard’s cricket frog in Trempealeau County, where it was last documented in 1965. Cricket frogs were also discovered in La Crosse and Buffalo counties, where they have not been found since the 1980s.

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Blanchard's cricket frog

The Blanchard’s cricket frog is typically ½ to 1½ inches long.

Officially known as acris blanchardi, the frogs — which are about the size of a human thumb — were once found throughout southern Wisconsin, but over the last half of the 20th century populations plummeted, and it is now the state’s only endangered amphibian.

By the early 1990s, there were “only had a handful of populations left” in the far southwestern corner of the state, said DNR conservation biologist Andrew Badje. The reasons are unclear, though Wisconsin has always been the northern limit of the Blanchar’s range.

“It could be disease,” Badje said. “It could be habitat change or wetland loss, weather fluctuations.”

In 2015 one of dozens of DNR volunteers who do frog surveys said he thought he heard the unique mating call — which sounds like steel balls clicking together — in Trempealeau County wetlands.

“This year I got out and sure enough I heard some cricket frogs,” Badje said.

The reasons for the comeback are as murky as the cause of its decline.

Badje suspects that frogs from an established population in southeastern Minnesota got flushed across the Mississippi River during heavy rainfalls over the past several years. It’s also possible that climate change — ultimately a threat to the species — has pushed their range further north.

“Now that we are kind of living in what seems to be a warmer world they’re probably capable of doing a little better here,” he said.

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Cricket frog range map

Historical range of North American cricket frogs

Malcolm McCallum, a herpetologist with Langston University in Oklahoma who has spent his career studying the Blanchard’s cricket frog, said it’s also possible the frogs were there all along but their numbers were so small they avoided detection. With a few years of good conditions, population numbers can explode.

“They were probably at very low levels barely holding on,” he said. “They can pop up and quickly disappear.”

Badje said it’s too soon to tell if the Blanchard’s return to the Coulee Region is a sign of a statewide comeback. But it is a good sign.

“Any time you can catalog increases in distribution it’s a good thing,” Badje said. “We’re going in the right direction.”

Carolina wrens in Wisconsin, prairie in the Boundary Waters

Whether climate change has anything to do with the Blanchard’s re-emergence, warming trends in the upper Midwest have altered the biological landscape.

Cold weather species are struggling to survive in the northern parts of Wisconsin and Minnesota, while plants and animals that traditionally thrive at much lower latitudes have moved in.

“We are seeing a lot of species shifting their ranges — locally and globally — in response to climate change,” said Jonathan Pauli, an associate professor of wildlife ecology at the University of Wisconsin-Madison.

In Wisconsin the southern flying squirrel has pushed into the north, displacing northern flying squirrels. Birds native to the southeast, like the tufted titmouse and Carolina wren, are now common.

Meanwhile, species like the ruffed grouse that depend on snow cover “are finding themselves in an increasingly hostile landscape,” said Ben Zuckerberg, another UW-Madison ecologist who has studied the impacts of climate change in the Midwest.

Zuckerberg points to the example of the snowshoe hare, which is native to northern Wisconsin and turns white in the winter.

“They’ve adapted over their entire life history to match with snow cover,” Zuckerberg said. “Because everything likes to eat snowshoe hare.”

As the days grow longer in the spring, the hare’s coat turns back to brown. But in recent years, the snow cover is disappearing earlier, leaving them “increasingly mismatched with this brown background.”

Plants, too, are responding to the climatic changes.

Since 1990, the coldest nights of the year have gotten about 5 degrees warmer, which means plants that used to grow in central Iowa can now survive in the Twin Cities, and red maple trees are now abundant in northern Minnesota’s Boundary Waters.

“Everything’s changing, and we’re just at the very beginning,” said Lee Frelich, director of the University of Minnesota Center for Forest Ecology. “We’ve only experienced about a fourth of the warming we expect by the end of the century. The really big changes are to come.”

Frelich said under the current models, the boreal forest would disappear in Minnesota and Wisconsin.

“The balance point between forest and prairie could move all the way up to Thunder Bay,” he said. “We could have prairie in the Boundary Waters.”

McCallum said while it might seem that Blanchard’s frogs could benefit from a warming climate, the results could be devastating. Because the frogs don’t truly hibernate, they tend to emerge during warm snaps, burning up their reserves of energy.

“You can go out in January and find them jumping around if it’s a warm day, but there’s really nothing to eat,” he said. “

Combined with other environmental threats — from habitat loss to hormone-disrupting herbicides — McCallum said there’s a danger of “death by a thousand paper cuts.”

“The complexity of what we’re doing to the environment creates problems that are very difficult to identify,” he said. “It’s not just frogs. It’s affecting ground squirrels. It’s affecting cows. It’s affecting your next-door neighbor.”

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Rhymes with Lubbock. La Crosse Tribune reporter and data geek. Covers energy, transportation and the environment, among other things. Call him at 608-791-8217.

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