RENO, Nev. — Scientists across the West are raising concerns about a growing infestation of exotic deer lice that appears to be killing Columbian black-tailed and mule deer and recently turned up in Nevada.
Researchers said the non-native lice first appeared in the mid-1990s. They apparently weaken the deer during the long winter months, causing hair loss and distracting them from threats posed by hungry predators like mountain lions.
The infestation has been on the rise, especially in Oregon, Washington, California and New Mexico.
“We’re very concerned about the potential impacts on the deer population,” said Greg Gerstenberg, a senior wildlife biologist with the California Department of Fish and Wildlife.
“The potential impact of exotic lice and hair loss could be devastating,” he told the Reno Gazette-Journal.
Nevada’s first case was reported in 2011 in the north-central part of the state in Smokey Valley near Tonopah. Suspected cases also turned up last year near Fallon about 60 miles east of Reno and in far eastern Nevada on a ranch near the Utah line south of Great Basin National Park.
“We have basically documented that we have it across the whole state,” said Peregrine Wolff, a veterinarian for the Nevada Department of Wildlife. She said that while the lice aren’t posing any widespread problem in Nevada yet, the issue could become a concern if it begins to impact deer populations to the degree it appears to be doing elsewhere.
“More and more states are identifying this,” Wolff said. “No one has been able to come up with a common thread with what’s going on.”
For the deer, what’s going on is decidedly uncomfortable. While native lice are common with deer and pose no particular problems, these exotic lice are another matter. They can infest deer in immense numbers in an itchy assault that, to a large degree, is targeting fawns.
“They will have thousands of lice on them,” said Gerstenberg. “It has to be an extreme irritation.”
Thus, the primary reason for hair loss, he said.
“They’re just almost nonstop biting, scratching, chewing,” Gerstenberg said. “In effect, they’re pulling their hair out.”
It appears the practice can prove fatal. During heavy winters in 2009-2010 and 2010-2011, mortality rates of 30 to 50 percent were recorded for mule deer in Stanislaus National Forest near Yosemite National Park.
With patches of hair gone, it’s harder for deer to stay warm, resulting in a dangerous energy drain that could lessen their chances of making it through a long, cold winter.
There’s another danger as well.
Many of the deer exhibiting hair loss found dead in Stanislaus National Forest had been attacked by mountain lions. Scientists speculate lice-infested deer may have been so busy grooming themselves they ignored the presence of approaching predators like lions and coyotes.
“They’re not paying attention,” Gerstenberg said. “It’s possible predators can approach the deer a little more easily.”
What appears clear, Gerstenberg said, is that the lice could affect survivability of a migratory mule deer population already on the decline for 20 years. He and others are now studying how serious that impact might ultimately be.
“We’re trying to assess what the impacts are,” Gerstenberg said. “We know we can’t get rid of the lice. We’re trying to determine if there is anything we can do to minimize their impacts.”
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