The deer in the backyard suffered through a long winter, but I thought they would have dined well and regained their weight this summer, with the all the rain and lush growth of the forest understory.
A deer’s summer coat of hair is much thinner than their winter coat, because it has no insulative underfur and consists of just one-inch long guard hairs that are gray next to the skin and reddish at their tips. Unlike horses, deer have few sweat glands and can’t evaporatively cool in the summer heat, so they rely on convective air movement through the short hair coat instead.
However, reducing the thickness of the hair protection can make deer vulnerable to biting insects, and there certainly are a lot of those out in the backyard this summer! Deer can become infected with microscopic mange mites, which can cause hair loss and skin scabbing, but only in an animal whose normal immune system is compromised in some way — old age or disease. It could be that is what this doe is experiencing.
Eurasian lice cause itching and excessive grooming in deer in late winter and early spring, and the deer eventually chew away the external layer of guard hairs, exposing the whitish or yellowish underfur. Eur-Asian deer and antelope don’t seem to be bothered by this louse, but infections of this introduced louse have killed Black-tailed and Mule Deer in the western U.S.
Walking through the wetland portion of the deep backyard is rather unpleasant right now, with hordes of mosquitoes and deer flies seeking out any exposed skin. It probably isn’t very pleasant for the deer either, whose thin summer coat offers less protection from biting insects.