A timber rattlesnake captured in Wisconsin shows signs of Snake Fungal Disease. The disease, which leaves bumps and scabs near the animal’s head and mouth, has been documented in four Wisconsin counties. The mysterious fungus is killing snakes in several states. Credit: Joshua M. Kapfer /University of Wisconsin-Whitewater

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A fungus that's killing snakes in Wisconsin and several other states — including endangered rattlesnakes — is baffling scientists who are trying to figure out how it's spreading.

Wildlife biologists are comparing it to white-nose syndrome, which is devastating bat populations. The mysterious disease has been documented in timber rattlesnakes in four Wisconsin counties: Sauk, Grant, La Crosse and Trempealeau.

Snake fungal disease leaves bumps, scabs or crusty scales on the head and mouth.

"It's not a good death," said Rori Paloski, a Wisconsin Department of Natural Resources conservation biologist. "A lot of the deformities are on the face and mouth. A lot of them die from starvation or dehydration because they can't eat or drink."

Last year Wisconsin's DNR was awarded a two-year grant of $10,000 from the U.S. Fish and Wildlife Service to monitor nine sites where timber and massasauga rattlesnakes live.

Timber rattlesnakes are listed as threatened or endangered in several states, though not in Wisconsin. Massasauga rattlesnakes are endangered in Wisconsin.

At two of the sites, DNR biologists and volunteers are implanting microchips similar to those used in dogs and cats. At the other seven sites, snakes are being captured and assessed. Any with mysterious lesions or signs of snake fungal disease are biopsied and sent to the National Wildlife Health Center in Madison, said Rich Staffen, a DNR conservation biologist.

First discovered in a captive black rat snake in Georgia in 2006, snake fungal disease has been found in numerous snake species in the eastern United States and the Midwest.

Unlike white-nose syndrome, which was first found in 2006 in New York and has steadily moved westward, there has been no discernible pattern for the spread of snake fungal disease, Paloski said.

The disease has also been found in Illinois, Minnesota, Ohio, Tennessee, Florida, Massachusetts, New Jersey and New York. Some states have reported serious declines in snake populations.

Though four cases have been confirmed in Wisconsin, it's likely more snakes have died from the fungus here.

"Looking back at pictures from previous years when we didn't know we had it, we figured out we probably had it in several more species," Paloski said.

Scientists are trying to figure out how the fungus spreads and are developing a test to identify it at an early stage so snakes can be treated.

"One of the things we're focusing on — it's likely spread through hibernacula sites when snakes are in contact with each other. But whether it's through the soil or airborne or some other way, we're not sure," Staffen said.

how to help

The DNR is seeking the public's help in surveying for snake fungal disease. Anyone who sees a snake with bumps, scabs or crusty scales is asked to take a photo and email it to richard.staffen@wisconsin.gov.