Washington wildlife officials estimate about 50 percent of the deer population in two central Washington counties has been lost since 2004, and while all the causes aren’t known, at least one is believed to be lice.
Officials in Yakima and Kittitas began receiving reports about black-tailed and mule deer with hair loss syndrome in 2002. The deer population began declining in 2004.
Test samples indicate the type of lice causing the problem – Bovicola tibialis – typically is found only on European fallow deer, which had been farmed in central Washington.
According to reports by the state Department of Fish and Wildlife, some of those deer may have escaped, inadvertently introducing the lice into the local environment.
Game farms have since been banned in Washington, though several existing ones have been allowed to continue operating.
“This is a new situation in Eastern Washington,” said James Mertins, an entomologist with the U.S. Department of Agriculture who was the first to discover the exotic lice species had invaded the area.
The chewing lice cause deer to begin obsessively grooming or rubbing. Bald patches then begin to appear, which make the deer more susceptible to environmental stresses.
David Darda, associate dean of biological sciences at Central Washington University, said the native deer’s ability to overcome this infestation will depend heavily on its genetic diversity.
“If you’ve got a decent genetic variety, you may have a large die-off initially, but as time goes by the variety can improve the deer’s ability to fight,” Darda said. “It’ll be interesting to see what happens in five years.”