The San Francisco Chronicle reports that since 2009, researchers have collected hair and blood samples from more than 600 deer and elk with symptoms ranging from a scruffy-looking coat to almost complete baldness.
The hair loss has been linked to an invasive species of lice that normally feeds on fallow deer native to Europe and Asia.
A spike in deer mortality appears to be associated with internal parasites spread by the lice.
Also predators like cougars and coyotes have an easier time hunting deer because of poor health and lack of attentiveness due to their feverish itching.
The deer population in Tuolumne County has been hit the hardest.