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University of Wyoming researchers continue to collaborate with the Wyoming Game and Fish Department (G&F) to identify toxins in lichen that are apparently weakening elk in the Red Rim area southwest of Rawlins to the point they are unable to stand.
Approximately 80 elk unable to stand have been killed by G&F personnel since the beginning of March. A similar die-off occurred in early 2004, when more than 400 elk unable to stand were found in the Red Rim-Daley Wildlife Habitat Management Area (WHMA) south of Interstate 80.
"We were hoping we would never see this again, but we are. It seems to be reoccurring this year," said Becky Dailey of Cheyenne, a Ph.D. student in UW College of Agriculture's Department of Veterinary Sciences.
Dailey, who has visited the site twice this month, added, "The elk are alert, but they are not able to get up. It's pretty depressing to see."
Researchers are confident the culprit is Xanthoparmelia chlorochroa, a lichen common to many areas of Wyoming and the West.
Dailey, who is focusing her research on the lichen, is working with Merl Raisbeck, a professor in the Department of Veterinary Sciences, to identify and quantify secondary metabolites in X. chlorochroa.
In explaining the secondary metabolites, Dailey said, "They have no known primary function in the metabolism of the lichen, but it's thought these compounds serve to protect the lichens from herbivores, insects and ultraviolet light. They are also thought to play a role in rock mineralization."
In 2004 and 2005, Dailey said, researchers collected X. chlorochroa from the Red Rim-Daley WHMA.
One group of sheep at UW's Wyoming State Veterinary Laboratory (WSVL) was fed a 100-percent diet of the '04 lichen, and another group received a 100-percent diet of the '05 lichen.
X. chlorochroa was also collected from areas near Cody and south of Laramie in 2006, and this lichen was also fed to sheep at the WSVL.
All the sheep produced red urine, Dailey said, but only the group fed lichen collected from the Red Rim in 2004 (the same year as the large elk die-off) was severely affected. Those sheep displayed similar symptoms as the Red Rim elk.
Sheep fed lichen collected from Red Rim in 2005 were least affected, while the Cody and Laramie lichen groups displayed some incoordination but nothing as severe as seen in the 2004 group, she said.
Why would X. chlorochroa in a specific area like the Red Rim be poisonous one year and not another?
"That's a really good question, but I don't think anyone has an answer yet," said Todd Cornish, an associate professor in the UW Department of Veterinary Sciences who is assisting Dailey, Raisbeck and others in the study.
"My guess is that it has something to do with environmental conditions. That is something that should eventually be pursued, possibly out of our department or someone else's, but right now we're trying to identify the toxins," Cornish said.
Dailey said several long-time ranchers in the Cody, Douglas and Jeffrey City areas told her they had cattle in areas where the lichen occurs show similar signs of incoordination as the elk, but, once the cattle were fed hay, most recovered.
Testing at the WSVL determined that several of the Cody- and Jeffrey City-area cattle had consumed X. chlorochroa.
Despite attempts to feed sick elk at the Red Rim area, animals did not recover, perhaps because they were in such a weak state when they started consuming the lichen, Cornish said. Elk are grazing animals, typically foraging on grass. The 2003-04 and 2007-08 winters were particularly harsh in the Red Rim area, and elk ate apparently whatever they could find.
"Both of those winters were heavy snow years, and the elk were in poor nutritional condition going into this," Cornish said.
Dailey added, "Large amounts of lichen and cactus are being found in their rumens during our necropsies."
Dailey is hopeful that, once the toxic compounds are identified in the lichen, a treatment can be discovered to aid game managers and ranchers treat stricken animals.
"It's frustrating that we can't do anything yet," Dailey said. "We are working on answers, but we don't have them yet."
Assisting in the laboratory studies are UW Department of Veterinary Sciences' Ph.D. student Dave Edmunds of Roanoke, Va.; master's students Amanda Fluegel of Dakota, Ill., and Laura (Linn) Meadows of Wilson; and G&F personnel including Cynthia Tate, assistant state G&F veterinarian stationed at the WSVL.
Tate and other G&F personnel are leading the field investigation.
Cornish added, "Many others here in the WSVL and elsewhere are helping us rule out other possible diseases in this investigation."