(Phyllis Carlson photo) This baby flying squirrels was one of three that former wildlife rehabilitator Phyllis Carlson of Quinnesec had to raise in spring of 2020 after someone cut down a tree and found them inside, the mother dead. It shows off the large eyes of this nocturnal species, the only tree squirrel that is active at night.

While locking the back door at night, a movement on one of the hanging suet feeders caught my eye.

It wasn’t wind making it sway, but a creature that poked out its head to look at me, then sprang to one of the deck posts to scramble away.

I can’t say I got a great look, but I didn’t need to — given the late hour, the darkness and the behavior, it most certainly was a flying squirrel.

While common, the flying variety is the most rarely seen of the squirrel species in the northwoods because it’s normally only active at night.

The Upper Peninsula can expect to have only four tree squirrel species at best — red and gray the most common, plus the larger and more scarce fox squirrel and the flying squirrel.

But while the first three are fairly closely aligned with each other and definitely favor the daytime hours, the flying squirrel is unique in being nocturnal.

It also is built different. It has large, dark eyes — a clue of its nighttime habits — and a dense coat that prompted the Minnesota Department of Natural Resources to declare on its website that “only the shrews and moles have fur that comes close in softness and silkiness to that of flying squirrels.”

North America has three species of flying squirrel — the northern that can range through Canada and into Alaska; the southern, primarily in the eastern U.S. but also in small pockets of Mexico and Central America; and the Humboldt’s, a Pacific Northwest variety only recently classified as separate from the northern.

They have a varied diet that sounds gourmet — truffles and mushrooms, lichens, acorns and other hardwood nuts and mast, conifer seeds, fruit, tree buds, insects, bird eggs and probably chicks if they can find them, as they “readily consume meat when available,” according to the Wisconsin Department of Natural Resources.

They in turn can be eaten by owls, hawks, fisher, martens, foxes, bobcats and lynx, even weasels.

Northern flying squirrels are thought to hoard food for the winter, though this has not been confirmed, the University of Michigan Museum of Zoology’s Animal Diversity Web site states at https://animaldiversity.org/. Those late-night habits make flying squirrels difficult to study, so their habits aren’t as well-known as the other tree squirrels.

While the U.P. likely has northern flying squirrels, the southern species has been advancing north with climate change, with northern Wisconsin being the southernmost point for the northern species. The northern and southern are very similar — the northern is slightly larger at about 11 inches in length to 9 for the southern, plus has more cinnamon color and a gray base to its white belly fur. Hybridization is known to occur where the species overlap. The northern flying squirrel is listed as a species of special concern in Wisconsin, according to the Wisconsin DNR.

Flying squirrels do not hibernate but slow their activity in winter and sometimes nest in groups to stay warm. This habit sometimes can lead them to find their way into homes. During the warmer months, females are territorial, males are not.

The world’s roughly 50 flying squirrel species can be found on only three continents: the three in North America; the Siberian in only three countries in Europe, Finland, Estonia and Latvia; and the rest in Asia. In contrast to our relatively diminutive varieties, the largest — the red giant flying squirrel of Asia from Afghanistan to southern China, Java and Sri Lanka — can be up to 4 feet in length, though about half of that is tail.

They are almost completely confined to the northern hemisphere, with none in South America.

Yet in an excellent example of what’s called “convergent evolution,” Australia has a look-alike in the sugar glider, a marsupial in the possum family that has similar skin flaps and the large eyes and nocturnal habits of the flying squirrels.

The gliders being marsupials and the flying squirrels placental mammals in the rodent family, the two are at best distantly related, according to online sources. An article published in the online journal eLife in October 2018 states that fossil records indicate flying squirrels evolved from tree squirrels at least 31 to 25 million years ago.

Southeast Asia also has the colugos, or flying lemurs, which are related to the primate family but have the same ability to glide through the rainforests on skin stretched between their limbs; they have flaps attached from the back legs to the tail as well. They, too, are nocturnal but unlike the sugar gliders look far different from our flying squirrels.

I expect the local flying squirrels will make more visits to the feeders with the region now fully transitioned to winter. So I’ll see if one of the trail cameras can’t be set up to perhaps capture one when it returns.

Betsy Bloom can be reached at 906-774-2772, ext. 240, or bbloom@ironmountaindailynews.com.