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Snakes have a well-earned reputation as silent and deadly killers. But there's another predator that quietly hunts in the wild. It's called snake fungal disease and they appear to be no match for it.
If the fungus known as SFD continues to devastate snake populations in the United States, the eastern massasauga rattlesnake could soon be a goner, according to a study announced Monday by the U.S. Geological Survey. So could the Louisiana pine snake.
"Some snake populations in the eastern and Midwestern U.S. could eventually face extinction as a result of SFD," Jeff Lorch, a USGS scientist and the lead author of the report, said in a statement released by the agency. "Our new findings increase our understanding of the geographic extent, species susceptibility and manner of development of this disease. These results will offer important clues regarding how to manage SFD."
The entire timber rattlesnake species found in the coastal southeastern plain isn't as threatened as the other two, but populations in certain areas of the South could disappear, Lorch said. It's not that the disease is lethal enough to take out an entire species of snake; it just helps finish the job that humans have started by expanding into the animal's habitat, squeezing it out of its home, and killing it outright.
"This is more . . . a contributor to habitat destruction and purposefully killing snakes. People don't like them," Lorch explained.
It's true that people generally don't like snakes. It's also true that they don't know how snakes help people. Without them, there would likely be more mice inside homes. They prey on pests - insects and other creatures - that hurt farm crops. Diseased rodents disappear into their mouths. Snakes in turn are food for other serpents that specialize in eating their kind.
Because of SFD, there are fewer of them. Its symptoms - thickened skin, ulcers, blisters, lumps, emaciation and disfigured bodies - first gained attention in 2006, according to the USGS. It was added to a list of mass killer diseases afflicting reptiles: Pseudogymnoascus destructans, a bat killer, had a lot in common with Chytridiomycosis, a mass killer of frogs and other amphibians. Ophidiomyces is the proper name of the snake slayer.
Scientists don't know if the fungus is spreading because they don't know where it started or how it expanded. They only know that they keep finding it wherever they look for it. Three years ago they detected it at nine sites. That number has more than doubled.
Between 2009 and last year, scientists examined samples from 82 wild snakes submitted to the USGS National Wildlife Health Center in Wisconsin and found that 76 percent had skin abnormalities and were positive for the fungus. "It really likes keratin that makes up skin," Lorch said, and "it's specialized to snakes." The study is published in the journal Philosophical Transactions of the Royal Society B.
With the help of state natural resources departments in Wisconsin and Minnesota, USGS scientists also captured 206 snakes from those states for two years ending in 2015 as they emerged from hibernation in late April to late May. "Forty-one percent of the captured snakes had skin lesions similar to those associated with SFD, and almost all of the lesions were relatively mild. Over half of the samples tested from these snakes were positive for the O. ophiodiicola fungus," the USGS said.
Lorch said he can't estimate how long it takes for the fungus to kill a snake because their resistance is different. Likewise, he has no idea how long it could take for a species like the eastern massasauga rattlesnake to disappear.