Flying Squirrel

There are two species of flying squirrels native to Wisconsin: the northern flying squirrel and the southern flying squirrel. Both species are protected and very similar in appearance. Unlike tree squirrels, flying squirrels are nocturnal, which means they are most active at night. They can be distinguished from tree squirrels by their very large eyes, flattened tail and furry patagium, a loose flap of skin that allows them to glide.

The northern flying squirrel is found in the northern third of the state and is a species of special concern. It is larger than the southern flying squirrel and is found in more remote conifer or mixed stands of conifer-hardwood forests. Northern flying squirrels nest in tree cavities or externally constructed nests called dreys. Females typically give birth to a litter of two to three pups between May and July, but they can have up to six pups in a litter. They usually give birth to one litter per year, but they may give birth to a second litter mid-summer if the first litter is unsuccessful, or particularly if they are found in the southern portion of their range. Pups are born without fur, and their eyes and ears are closed. Their eyes will open after about 25 days, and the pups are cared for by their mother until they are weaned at around 2 months old. In some cases, they may stay together for a few additional months.

The southern flying squirrel is smaller in size, more widely found throughout the state and often inhabits residential areas or hardwood forests. Southern flying squirrels nest in tree cavities and females give birth to litters of two to three pups, but can have up to six, in April or May and again in August after a gestation of 40 days. The pups are born without fur, and their eyes and ears are closed. After about two weeks, the pups will be covered in fur, and their eyes will open after about a month. The pups are cared for by their mother until they are weaned at around 2 months old, but in some cases, they may stay together for a few additional months.

Tip: Flying squirrels will sometimes build their nests in man-made structures such as attics or well-constructed bird houses, and it is important to understand what actions can be taken, especially during the pup-rearing season from May 1 through Sept. 30. Please refer to the Flying Squirrel FAQ for more information.