Guys - this is indeed Hairloss Syndrome...all of them. Dr. Briggs Hall, from WDFW. He's THE expert on this condition. I attended a training session led by Dr. Hall several years ago about how to recognize deer affected by this condition, the cause (parasite ingestion from slugs or snails), and participated in a field reporting program over a couple years time. Don't be confused by "color". Piebald condition in deer looks completely different. The condition can vary from mild to severe, which can and does lead to hypothermic death.
from the WDFW web site:
Deer Hair-loss Syndrome: Dr. Briggs Hall has had several long discussions with Dr. Jack Mortenson of the USDA regarding the hair loss syndrome. Evidence is mounting that the lice causing our black tailed deer to groom excessively is an exotic louse species. A second louse expert from Oklahoma has concurred with Dr. Mertins at NVSL that the lice are in fact an exotic species. Oregon has submitted a number of louse samples from both hair loss deer and normal deer, including mule deer. The samples have been submitted without information as to where they came from or the condition of the deer. In every case, the experts have identified the lice from the hair loss deer as the exotic louse Damalina cervicola, and the lice from the normal black tailed deer and mule deer as the normal deer louse Damalina tricholipeurus.
