Hair loss in squirrels can be caused by mange or fungal disease. Mange is a disease caused by microscopic mites that burrow under the skin. The squirrel mange mite has been reported in both fox and gray squirrels. There have been no reports of this type of mange being transmitted to humans or domestic pets. Loss of hair, and dark, thickened skin are symptoms of mange in squirrels. Mange can be spread by direct contact between squirrels. Adult squirrels in good condition typically survive mild infestations, but severe infestations are often fatal. Additionally, infected squirrels with a lot of hair loss may die of exposure during the winter. Another possible cause of hair loss in squirrels is fungal disease. A variety of fungal diseases affect squirrels. The fur of infected squirrels will break off at the skin leaving patches of skin that appear to be bare. Otherwise healthy squirrels will recover from fungal infections. There is not much that you can do. If you feed squirrels, try putting out smaller quantities of food at more sites around the yard rather than at one or two large feeding stations. Contact with other squirrels at the feeding stations can help spread mange. Stopping feeding completely isn't necessarily recommended since the squirrels likely depend on the reliable source of food. If you don't currently feed squirrels (or birds), do not start. Squirrel and bird feeders attract more animals to an area than would normally be present. And the animals are in closer contact with one another than they would be under normal feeding conditions in the wild. This increases their chance of spreading disease. Wild animals are very good at finding their own food. If people enjoy attracting birds to their yard, they should consider planting native flowers, shrubs, and trees. This way of feeding the birds (and other wildlife, like squirrels) provides them with natural food sources that are dispersed in the yard, which helps keep the spread of disease low.