Air rescue: Saving Pennsylvania’s northern flying squirrel

By Kathy Hackleman, Senior Editor/Writer, Penn Lines
Reprinted with permission from Penn Lines / Pennsylvania Rural Electric Association

adult flying squirrel in Texas - photo by akire-tanzt

It is almost impossible to distinguish between a northern flying squirrel and a southern flying squirrel without close observation of the hairs on their chest (if the hairs are white from tip to base, it’s a southern flying squirrel; if they are white at the tip, but darker at the base, it’s a northern flying squirrel). While to the average Pennsylvanian, it appears as if one could easily be substituted for the other, they are very different.

The southern flying squirrel, with its disproportionately large eyes, conspicuous skin flaps and a flattened tail to assist in gliding, is prevalent in much of the state. However, these nocturnal creatures go about their lives seldom noticed — unless they inadvertently end up in a chimney with no way out. When they are seen gliding from treetop to treetop to rooftop in the darkness, they are often mistaken for a bat or a bird. Once found only in the southern United States, they have slowly but steadily crept northward until they have taken over much of Pennsylvania.

The northern flying squirrel, on the other hand, is in trouble despite its almost-identical appearance.


“The northern flying squirrel, which is listed as endangered in Pennsylvania, is a part of the state’s historic population of wildlife,” says William M. Williams, information and education supervisor for the Pennsylvania Game Commission (PGC). “It is a native Pennsylvania species that was here prior to the European colonization. Because of human behavior in destroying their habitat, the conifer forest, they have been wiped out in Pennsylvania almost entirely.”

However, there is a group of people determined to halt the decline in the northern flying squirrel numbers and, if possible, increase their population in the state through forest management.

Greg Turner, the PGC state mammologist, is one of those people. He has been studying northern flying squirrels since 1995 when he was a part of a study team at Wilkes University in Wilkes-Barre, Pa. He and his university colleagues wrote a grant to obtain funding specifically to determine the distribution of the northern flying squirrel in Pennsylvania.

“The northern flying squirrel is very rare and very difficult to find,” Turner reports. “It is a mammal that is very secretive and rare, so they get ignored by a lot of people because it takes a lot of time and work to figure them out, but I like the challenge.”

Fewer than 50 northern flying squirrels have been located in Pennsylvania since 1995.

“That gives you a good idea of how rare they are,” Turner says. “I have personally handled around 30 of those. In an effort to locate where they are, we have placed over 700 nest boxes across the state, and we have also done some live-trapping. Live-trapping is a very labor-intensive process as we bait the traps in the evening and check them at first light daily because our primary goal is not to harm any of the species.”

flying squirrel in squirrel house

Electric cooperative members in territories served by Cambridge Springs-based Northwestern Rural Electric Cooperative (REC), Youngsville-based Warren EC, Mansfield-based Tri-County REC, Wysox-based Claverack REC and Forksville-based Sullivan County REC are the most likely Pennsylvanians to observe the elusive critters in the wild. The majority of the northern flying squirrels captured in recent years have been in the Poconos, though one was captured in Warren County and one was found in Potter County.

Because it can take thousands and thousands of hours to corral just one flying squirrel in a live trap, researchers are taking a new path.

“We are using ultrasonic acoustic detectors, recording them as they communicate by chirping,” Turner says. “We have isolated their chirp, and we record for a week or two in a specific location. The problem is that the detector is set off by anything, bats flying by, raindrops, a deer stepping on a stick. Just from last year, we have 600 gigabytes of files to go through. There’s no way to go through that much material to find a single chirp, so we are working on the last step, getting an automated computer program to sift out northern flying squirrel calls.”


“You need lots of people with specific skills, including statistical analysis and research, someone who is good with fungi and lab work, people who know mammals, foresters and ecologists, people on the ground with the game commission to help us manage habitats,” Turner says. “We all partner up to get it done. Without everybody, we wouldn’t have this story. It is truly a collaborative effort.”

In the meantime, these interested groups and individuals aren’t just focused on knowing the current status of the northern flying squirrel in Pennsylvania. They have developed a plan they hope will slow and ultimately reverse the population decline. They know the major reason for the decline.

PGC employees collect red pine cones
LOOKING TO THE FUTURE: Pennsylvania Game Commission employees gather red spruce cones to plant at a state nursery. When the seedlings are ready, they are transplanted to state-owned land, with the expectation they will eventually provide homes and food for the endangered northern flying squirrel. (Photo courtesy of the Pennsylvania Game Commission)

“One hundred to 120 years ago, much of Pennsylvania’s forests were clear-cut,” Williams explains. “Before that, the forests were filled with hemlock, white pine, birch and beech trees. A lot of what grew back were more southern species like maples and oaks. That’s when the southern flying squirrels started moving in, and now they are the most abundant squirrel in the state even though people don’t often see them because they are nocturnal.”

The two types of flying squirrels do not co-exist (the prevailing theory is that the southerns carry an intestinal parasite that is deadly to the northerns), but it is the lack of mature, conifer forests that has spelled the most danger for the northern flying squirrels. The loss of the conifer forest has not affected the southern flying squirrel as its food supply is much more varied, from eggs and insects to seeds and carrion.

“The northern flying squirrel is more of a food specialist,” Williams reports. “It eats a very specific, limited set of foods. One of them is the small fungi that grow underground on coniferous trees. The trees, fungi and squirrels are all working together; each has an essential role. The fungi is food for the squirrel. As the squirrels move around in the woods, they deposit spores, which allow the fungi to grow in other places. The squirrel needs the trees to live in and jump off of in order to glide. The tree needs the fungi in order to live as the fungi help the tree to acquire moisture during hot, dry summers. All three are dependent on each other.”


Because one of the traditional favorite homes of the northern flying squirrel — the hemlock — is in trouble itself from the spread of the invasive hemlock woolly adelgid, biologists and foresters are focusing on tree regeneration projects as the way to revive the northern flying squirrel population in Pennsylvania.

“A number of years ago, our foresters began anticipating that some of the areas where northern flying squirrel had been found traditionally were going to be affected by the hemlock woolly adelgid, so they began planting red spruces,” Williams says.

One of the duties of PGC employee Brian Stone, nursery manager at Howard Nursery, is to work with the Department of Conservation and Natural Resources (DCNR) to collect red spruce cones and nurture them until the seedlings can be planted.

“We take our binoculars and look up into mature red spruces to check for cones developing near the top of the tree,” Stone explains. “We work with DCNR to collect the cones and start them in our nurseries. Red spruce has a real niche where it grows. Most of the locations in Pennsylvania are in Sullivan, Wyoming and Luzerne counties (areas served by Sullivan County REC and Claverack REC).”

Cones are dried and stored until they are ready to be planted. Seedlings —  about 12 to 18 inches tall after three years — are provided to state employees, biologists, land managers and foresters, who plant them in state-owned forests. By hand.

“You wear a bag on your hip and you carry a spade that you shove into the ground; you bend over, plant the tree and ‘heel’ it in with your shoe,” Stone says. “There is nothing more satisfying, but it is really hard work.”

In an ideal world, Stone says, each pound of red spruce seeds would equal 100,000 to 280,000 trees. Of course, not every seed germinates, and not every seedling survives once it is left on its own in the wild.

The men and women who are dedicated to saving an endangered species know they have an extended, difficult project on their hands, but they believe it is worth it.

“All species have a role in our environment,” Turner says. “And while we may or may not understand what those roles are, and we may not find out what those roles were until we lose them, it’s too late then.”