Columbian black-tailed deer (Odocoileus hemionus columbianus) with signs of hair loss,

at Grays Harbor National Wildlife Refuge, Hoquiam, Washington.

About 25 years ago wildlife biologists first noticed black-tailed deer in western Washington and Oregon afflicted with severe hair loss, thought to be caused by hypersensitivity to Eurasian lice, coupled with poor immune function. Adult females and fawns are more likely to experience hair-loss syndrome, and afflicted fawns consequently experience higher mortality rates. Hair loss during late-summer molt usually results in a scruffy appearance, but the new growth of hair is visible through the patches. The deer in this photo has lost most of its hair across its back and haunches, with no sign of new hair.