Some Baby Boomers who were kids in the classic cartoon age might be surprised to learn that, yes, there is such a thing as a flying squirrel. "Rocky," brainy cartoon complement to Bullwinkle, really was inspired by nature. But that's the end of Rocky's link to reality.
For one thing, there are two species of flying squirrels in North America -- northern and southern -- both of which live in Pennsylvania. Rocky's animators made no attempt to distinguish which kind he was. Also, flying squirrels don't fly. They glide on flaps of furry skin, called patagia, that stretch from the front leg to the ankles of the back leg. The squirrels climb a tree, launch and glide to a lower position. Most glide lengths are 20 to 40 feet, but researchers have documented glides of up to 300 feet. During their coasts, flying squirrels steer by moving their furry tails from side to side.
Few people have seen these glides because flying squirrels are nocturnal. They forage at night and spend the day in tree cavities or loose nests of leaves and bark. Both species eat acorns, beechnuts, hickory nuts and other seeds of deciduous trees. The northern flying squirrel also utilizes more specialized foods, especially fungi and lichens associated with coniferous trees. Both squirrels also consume insects, bird eggs and even nestlings when available.
In fairness to Rocky's creators, it takes a trained eye to tell the two squirrels apart. Northern flying squirrels are slightly larger, almost 11 inches from snout to tail. Adult southern flying squirrels measure from 8 to 10 inches. Flying squirrels of both species seldom weigh more than one-fourth of a pound, while the familiar gray squirrel can weigh 2 pounds.
Both flying squirrels are brown on the back and white on the belly, but the northern exhibits a reddish tint on the back. The surest distinction is impossible to observe unless a squirrel is examined up close. On southern flying squirrels, the white hairs on the underside are white all the way to the skin. Belly hairs on the northern squirrel are whitish at the tip but grayish at the base.
The starkest difference lies in the kinds of places where the two squirrels thrive. Southern flying squirrels are habitat generalists and inhabit hardwood forests all across the state. They even do well in small woodlots and some suburbs. Surprisingly, surveys indicate that southern flying squirrels may be as abundant as gray squirrels.
A researcher who has studied flying squirrels for nearly a decade says many people could see a flying squirrel if they knew where to look.
"If you live near woodland, or even in a suburb where lots of trees were left standing, check your bird feeder at night," said Carolyn Mahan of Penn State University. "Flying squirrels are shy, but they often frequent bird feeders for the seed. Shine a light there and you may get the pleasure of seeing one."
If you do, Mahan said, it will probably be of the southern species. Northern flying squirrels are rare in Pennsylvania. The species was added to the state's list of endangered species in 2007.
"The northern flying squirrel is conifer-dependent," Mahan said. "They must have hemlock and spruce. Unfortunately, that habitat type is under stress now. We are losing hemlock to the hemlock woolly adelgid [an invasive insect] infestation. Also, the core range of the species in Pennsylvania is the Pocono Mountains, and those habitats are under stress from residential development."
The northern flying squirrel faces a two-pronged attack.
"As the hemlocks die, the southern flying squirrel moves in. It carries a parasite that is lethal to the northern flying squirrel," Mahan said.
Still, there could be hope for the northern species in Pennsylvania, inspired by its resurgence in West Virginia.
There, the northern flying squirrel had a stronghold in the high elevation red spruce forest on the Allegheny Plateau. Hundreds of years ago, fingers of that same red spruce forest pushed north across Pennsylvania's ridges.
West Virginia's northern flying squirrel almost vanished when the state's red spruce belt was logged between 1880 and 1950. But the high mountain red spruce forest is returning in West Virginia, and with it the northern flying squirrel.
According to a report from the U.S. Forest Service Northeast Research Station in Parsons, W.Va., "The single most important factor in the [northern flying] squirrel's population resurgence in West Virginia has been the regeneration of its forested habitat."
Mahan believes that northern flying squirrel habitat in parts of Pennsylvania can also be restored.
"The good news is that we are beginning a red spruce restoration project in Pennsylvania," Mahan said. "It's a partnership between Penn State, the Department of Conservation and Natural Resources and the Game Commission, funded by the Wild Resource Conservation Fund. Our pilot project is in the Poconos. We'll plant red spruce seedlings and monitor them over time. We hope red spruce can replace lost hemlocks and provide habitat for the northern flying squirrel."
Mahan sees other payoffs. "If we can get red spruce back, it would benefit trout streams by shading them and keeping them cool. The whole conifer ecosystem would benefit," she said.
Once the Pocono project is under way, Mahan will be looking to expand the restoration.
"The Laurel Highlands is one region we'd like to survey for northern flying squirrels," she said. "They may be there in small numbers, and we're interested in extending our red spruce project there. It could provide a corridor between populations in West Virginia and northern Pennsylvania."