Hang Gliders of the Alaska Night: Northern Flying Squirrels

After a decade in Alaska without seeing a northern flying squirrel, I held one in my hands the other day. It was soft and velvety. Unfortunately, it was also dead.

That particular flying squirrel rests in a drawer in the basement of the University of Alaska Museum in Fairbanks. Gordon Jarrell, a research associate who manages the museum's mammal collection, gave me a glimpse of the stuffed flying squirrel. Few people have seen these furry kites of the forest, even though they're not rare in Alaska.

The northern flying squirrel's large, teddy-bear eyes hint at why the creature is so hard to spot--it's nocturnal. The lucky people who spot them usually see them dining at bird feeders in winter or gliding from tree to tree in the mid-summer, when the sleepless sun doesn't allow them to sail in darkness.

The northern flying squirrel performs its acrobatics everywhere there are trees in Alaska. The airborne rodent ranges as far south as California and the central Appalachian Mountains of North Carolina and Tennessee. Although flying squirrels are endangered in other parts of the country, Alaska boasts a healthy population, according to Bob Mowrey, a wildlife biologist who tracked flying squirrels near Fairbanks in the mid-1980s.

Flying squirrels are about as abundant as red squirrels, Mowrey said in a recent interview from his Olympia, Washington, home. The northern flying squirrel is a well-studied creature where Mowrey lives because it prefers to live in old-growth forests there, as does its celebrity predator, the northern spotted owl. A pair of nesting spotted owls can polish off 440 flying squirrels in a year, Mowrey said.

While tracking flying squirrels in the Bonanza Creek area south of Fairbanks, Mowrey often watched them "fly" from tree to tree. Using a loose membrane of skin that stretches from each fore to hind leg, a flying squirrel glides on air in a controlled descent from tree to tree. The animal's tail, which looks like a feather, is used as a rudder, Mowrey said. He's seen a flying squirrel travel 100 yards in the air before performing a "parachute flare" to slow itself and extend its hind feet to land lightly on another tree.

"They have no fear," Mowrey said of the flying squirrels' netless trapeze act.

Mowrey broke in a few pairs of boots while following the nightly movements of flying squirrels in the Interior. The tiny mammals glided and hopped as much as 1.2 miles each night in search of food. What they ate most came as a surprise to Mowrey-truffles. Truffles are a form of fungus that grow underground and are dependent upon small mammals to eat them and later spread their spores in fecal matter.

When winter comes and truffles become more difficult to find, flying squirrels don't hesitate to raid the food caches of red squirrels. Mowrey said he doubts if red squirrels even realize they've been robbed because the flying squirrels pilfer while the red squirrels (and most people) are sleeping.

Winter in the north changes the address of many flying squirrels, Mowrey said. Instead of nesting in poorly insulated tree cavities, which are fine during the summer, flying squirrels opt for witches' brooms. Witches' brooms are knotted snarls of branches caused when a rust fungus attacks spruce trees. Flying squirrels seek out witches' brooms and carve a hole in the middle of the spaghetti-like tangle. Once they excavate a hole, they line it with a sleeping bag of mosses, grass, feathers, scraps of wool, and any other dry insulating material they can find. When it gets so cold that Fahrenheit and Celsius scales agree (about minus 40), flying squirrels slow to a state of near hibernation, Mowrey said. The squirrels slumber for as long as it's really cold. Mowrey also noticed that flying squirrels share sleeping quarters in extremely frigid weather. The flying squirrels' behavior gave him a new definition of bitter cold.

"It's kind of like a three-dog night," he said. "In interior Alaska, it's a three-flying squirrel night."