- Associated Press - Friday, July 4, 2014

MOORHEAD, Minn. (AP) - Scientists in northern Minnesota are trying to decode frog sounds in hopes of understanding why the amphibians’ populations have been shrinking.

Frogs have been dying off because of disease, pesticides and habitat loss. But researchers didn’t know exactly how significant each factor was, nor could they study frogs by watching the elusive amphibians. So, they listened to frogs instead.

Scientists have set up recording devices in 34 sites across North America to collect five minutes of sound every hour, seven days a week. One site is in the Tamarac National Wildlife Refuge in Moorhead, where scientists have been gathering data for seven years across 10 wetlands.

By analyzing the data, researchers have been able to quantify the population die-offs. Between 2002 and 2011, populations of at-risk frog species fell nearly 12 percent. However, scientists were surprised to find that populations of all frogs, including those considered healthy, were down nearly 4 percent, Minnesota Public Radio reported (http://bit.ly/1o8t5SJ ).

Michael Adams, a research ecologist with the U.S. Geological Survey, said the results add to scientists’ concern for what’s happening to the amphibians.

“There’s still something else going on beyond what we knew was going on with the more critically endangered species,” he said.

The research included decoding frog sounds, which reveal when the amphibians are first active in the spring and when their mating season peaks. Researchers also monitor satellite images to track snowmelt and determine when the landscape turns from brown to green each spring, as well as monitor water and air temperature by seasons to understand how the climate is changing.

Adams says there might be different explanations for declining populations around the country, which he believes makes long-term monitoring important.

“It’s unusual to have ecological research projects that run for a long time,” Adams said. “It allows us to ask types of questions you can’t normally ask over shorter time frames.”

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Information from: Minnesota Public Radio News, http://www.mprnews.org

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