Why Do Squirrels Lose Their Hair?

Many people are concerned about the growing number of squirrels that appear to be losing their hair. Squirrel hair loss can be attributed to several different causes.

Mange

When most people see a squirrel with patchy hair loss, they assume that the squirrel has contracted a case of mange. Squirrel mange is similar to the mange contracted by other animals, but is caused by a different mite--the squirrel mange mite (Notoedres douglasi). Squirrels with mange usually recover and the missing hair grows back, although they may appear very damaged and ill during the course of the mange outbreak. No reports exist of squirrel mange being transmitted to humans or other animals.

Fungal Infections

Another cause of squirrel hair loss is a variety fungal infections collectively known as dermatophytoses. Squirrels with fungal hair loss do not actually lose their hair; it breaks off at the skin, making the squirrel appear bald. Most squirrels fully recover from dermatophytoses, although it takes time for their bodies to formulate the proper immune response.

Damp weather is believed to contribute to the growth of the fungi that cause dermatophytoses. This explains why, in many areas, spring seems to be the season when most balding squirrels are spotted.

Hereditary Causes

A third possible cause of hair loss in gray and fox squirrels is an inherited defect in which the hair fails to grow properly. These squirrels have hair follicles, but do not produce hair. Rather than losing their hair, squirrels with this defect never grow hair at all.

Poor Diet

Often hair loss is seen in captured and pet squirrels because of a dietary insufficiency. A lack of calcium will cause a squirrel's hair to grow poorly or to fall out. Other nutrients found in the wild that are necessary for proper hair growth may also be lacking in a captive squirrel's diet.

Metabolic Bone Disease

A final, and most unfortunate, cause of squirrel hair loss is metabolic bone disease. Metabolic bone disease is most common in captive squirrels. It is caused by a lack of Vitamin D in a squirrel's diet. Metabolic bone disease is preventable but often difficult to diagnose. Left untreated, it is generally fatal.