Northern flying squirrel

A nocturnal glider of old-growth conifer forests that eats mostly underground fungus and, under a UV light, glows bubblegum pink.

Northern flying squirrel at a glance

Glaucomys sabrinus FLY-ing SQUIR-el; Glaucomys sabrinus is glaw-KOH-miss suh-BRY-nus

Type
Mammal · rodent
Diet
Omnivore
Size
About as long as a school ruler, nose to tail (around 12 inches / 30 cm), and weighing about as much as a stick of butter (up to 4.4 ounces / 125 g). The 'wings' are really just loose folds of furred skin, not feathers.
Lifespan
Most live less than 4 years in the wild, though captive animals have lived 10 or more.
Conservation
Least concern

Eats truffles and other underground fungi, seeds and nuts, tree buds, flowers, and lichen, occasionally bird eggs or insects

About 90% of a northern flying squirrel's diet is truffles, the underground fruiting bodies of mycorrhizal fungi, which it digs up by smell in the dark. It fills out the rest with seeds, nuts, buds, and occasionally a bird egg or insect.

Should you worry?

No real risk. It's nocturnal, shy, and rarely seen at all, let alone up close. If a family finds one in an old woodpecker hole or under bark, look and don't touch, and leave the tree alone.

Swing a UV flashlight across the base of an old-growth conifer after dark, and the leaf litter can blink back in a color that has no business being in a rain forest: a hot, uniform bubblegum pink. That’s not fungus or lichen glowing. It’s the belly fur of a northern flying squirrel, caught mid-glide or paused on the bark, invisible under ordinary light and startling under UV, a trait biologists only confirmed in 2019 after testing squirrels and century-old museum skins from one end of the species’ range to the other.

The color is a mystery scientists are still working out. What isn’t a mystery is how this squirrel spends most of its night: digging. About 90% of its diet is truffles, the underground fruiting body of a fungus that wraps around conifer roots and trades nutrients for sugar. The squirrel smells one out, digs it up, eats it, and hours later leaves the fungus’s spores somewhere new in its droppings, still alive. Multiply that by every flying squirrel working an old-growth stand and you have one of the ways these forests keep reseeding the underground network their biggest trees depend on.

None of this happens where anyone can see it. The squirrel glides on a flap of skin stretched wrist to ankle, sometimes covering a few hundred feet between trees at 20 to 30 mph, always after dark, always gone before a flashlight beam finds more than a pair of eyes. The best daytime clue isn’t the animal at all: an old woodpecker hole in a standing dead tree, or a truffle dug up and half-eaten in the duff, is the sign that something was working the forest floor all night while everyone else was asleep.

Did you know?

  • A flying squirrel doesn't fly. It glides on a stretched-out flap of furred skin called a patagium, steering with its tail like a rudder, and can sometimes cover more than 150 feet between trees.
  • Under a UV flashlight its belly fur glows bright pink, a discovery scientists only confirmed in 2019 after testing squirrels and old museum specimens going back over a century.
  • It nests in old woodpecker holes and hollow snags, often sharing a fondness for the same big dead trees that pileated woodpeckers and spotted owls need.

Common questions

Can northern flying squirrels actually fly?

No. They glide. A flap of skin from wrist to ankle opens like a small parachute, letting them sail from a high branch to a lower one on another tree, sometimes for a few hundred feet.

What do flying squirrels eat?

Mostly a kind of fungus called truffles that grows underground, which they dig up by smell. They also eat seeds, nuts, buds, and sometimes a bird egg or insect.

Why do flying squirrels glow under a black light?

Their fur fluoresces bright pink under ultraviolet light. Scientists confirmed this in 2019 but are still studying why it happens.

Where would you actually see one?

Almost never in daylight. Your best clue is an old woodpecker hole in a big dead tree, or a chewed-open truffle in the dirt, since the squirrel itself only comes out after dark.

Where it lives

Where we got this