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Killer Fungus Targeting Endangered Rattlesnakes

The views expressed are those of the author and are not necessarily those of Scientific American.


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massasauga rattlesnakeIn 2008 biologists studying the eastern massasauga rattlesnake (Sistrurus catenatus catenatus) made a gruesome discovery: three sick snakes suffering from disfiguring lesions on their heads. All three died within the next three weeks. A fourth snake, found in 2010, also died from the mysterious growths and ulcers.

Necropsies uncovered the source of the lesions: a fungal infection called Chrysosporium. “Chrysosporium causes disease in bearded dragons and in other snakes, and it’s a bad bug,” according to Matthew Allender, visiting instructor at the University of Illinois at Urbana–Champaign, speaking in a prepared release. “We see it in captive animals worldwide, but we don’t typically find it in free-ranging animals.” Allender is the lead author of a paper on the fungal infection, which appears in the December 2011 issue of Emerging Infectious Diseases.

The infected rattlesnakes were all found in a park near Carlyle Lake, Ill., where a long-term monitoring program has been studying the eastern massasauga since 1999. The four snakes’ heads were covered in ulcers and swelling that extended throughout their skin and skeletal muscles, and obscured their nasolabial pits. One snake had an infected eye, with only a small fragment of its cornea remaining. The snake with the most severe infection suffered from extreme swelling around the maxillary fang.

Further testing revealed that the Chrysosporium fungi were molecularly related to samples from the diseased skin of a captive black rat snake. This suggests that the fungus could have come from released or escaped pet reptiles.

Allender first reported on his findings at a meeting of the U.S. Fish and Wildlife Service (FWS), after which he heard of similar infections that have occurred in other parts of the Northeast over the past five years. “They seem to be having a similar problem in timber rattlesnakes in New Hampshire and Massachusetts,” Allender said.

Allender called the Illinois infections a “yellow flag” that shows a need for further study.

The eastern massasauga, one of the smallest rattlesnake species, is a candidate for protection under the U.S. Endangered Species Act. It currently has no federal protection, although it is protected by state laws throughout its habitat, which extends from western New York State to southern Iowa. According to the FWS, the snake is threatened by destruction of wetlands and persecution by people who have an innate fear of venomous snakes.

Carlyle Lake is home to the only viable eastern massasauga rattlesnake population in Illinois, according to a report published in 2000 by the Illinois Natural History Survey.

Photo: United States Geological Survey (pdf)

John R. Platt About the Author: Twice a week, John Platt shines a light on endangered species from all over the globe, exploring not just why they are dying out but also what's being done to rescue them from oblivion. Follow on Twitter @johnrplatt.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Pugsley 8:50 pm 02/23/2012

    Well, stuff happens. I don’t think this is very important other than to other rattlesnakes and to mice or whatever they eat. It’s the way of the world, they either adapt to the fungus and loss of wetlands, or they become extinct. I’m betting that they will adapt, but if they don’t then something else will probably fill the niche.

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  2. 2. Lou Jost 10:53 pm 02/23/2012

    What a short-sighted comment, Pugsley. The loss of a high-level predator can have major consequences that ripple through all levels of an ecosystem. The worldwide human-mediated exchange of fungi, diseases, and pest insects and animals is a recent novelty, and is causing mass extinctions worldwide. Adaptation is usually a slow process compared to the rate of spread of a novel pathogen.

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  3. 3. coelacanth 11:52 pm 07/23/2012

    Pugsley, the article doesn’t discuss the ecological role of rattlesnakes. It mentions the viability of specific species. Just because they’re snakes doesn’t mean we can’t find them inherently valuable. And no, with the mass destruction of wetlands, it’s doubtful something will successfully and equivalently fill its already tiny niche.

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