Hairless deer are appearing across the state, especially in Tuolumne County, and they aren’t making a fashion statement.

They have lice, and it may be threatening their lives.

State officials began noticing the hair-deprived deer in 2009. They found 240 balding deer outside Yosemite National Park in a five-month period, and started a research project that is ongoing. Hair-challenged deer have been found in 15 counties, as far south as San Diego County. Deer in other Western states have reportedly been similarly afflicted.

Researchers have taken hair and blood samples from 600 deer and elk to date and attached tracking devices to them. A commenter on the California Department of Fish and Wildlife’s (CDFW) Facebook page, Molly Beth Jacobsen, said that in Humboldt County where she and her husband live and are avid hunters more deer than not are showing hair loss. She said it seems to have “greatly impacted” the deer population there.

Hair-loss syndrome is generally associated with bad nutrition, but investigators are coming around to the conclusion that it is the result of a non-native lice infestation. Until now, the species of lice has been known to feed on deer in Europe and Asia. 

In the past, the hair-loss phenomenon has been attributed to an “environmental deficiency of copper or selenium or some other underlying environmental factor such as a difficult-to-detect disease agent,” according to Pam Swift, a state veterinarian with the CDFW.

But wildlife experts have been zeroing in on the lice lately. Senior wildlife biologist Greg Gerstenberg was quoted on the department website speculating that the lice are becoming life-threatening to the deer because “louse-infested deer spend so much time grooming they become easy targets of predation by coyotes or mountain lions.” 

While that theory is still just speculation, Gerstenberg said the lice have already “impacted migratory populations of California deer.”

–Ken Broder   

To Learn More:

Balding Deer Being Ravaged by Exotic Lice  (by Peter Fimrite, San Francisco Chronicle)

Researching Lice Infestation (by B.J. Hansen, MyMotherLode)

Deer Hair-Loss Syndrome Challenges California Researchers (California Department of Fish and Wildlife)