Head down, legs spread, the flying squirrel glides among trees in the forest like an animated paper airplane.
"Last April, I was spring-cleaning bird houses for the returning nuthatches and chickadees that raise families there. The first few boxes contained bits of moss, feathers, and old nesting material. But when I opened the last box, I found it filled with strips of cottonwood bark and twigs, enough that it sent me down the ladder in search of a trash can. When I climbed back up, I was surprised by whiskers and a pair of black eyes poking out at me from the nesting material. A flying squirrel! Quickly I closed the box and backed down the ladder.
Flying squirrels are small grayish-brown tree-dwelling rodents with large, shiny black eyes. You can find them in the coniferous forests and riparian woodlands of Western Montana. A furry fold of skin stretched between ankles and wrists acts as a sail that allows flying squirrels to glide from tree to tree, or from tree to ground. They are not capable of actual flapping flight, but can glide up to 100 yards given a high enough launching point. Typical glides range from 20 to 50 yards.
Like us, red squirrels and the larger Eastern fox squirrels are active during the day. But flying squirrels don't come out until deep dusk and are tucked into bed before we get up, so we don't often see them. Most of my flying squirrel sightings have been brief nighttime encounters: a ghostly shadow drifting through the pines as my car headlights swept past, a swinging bird feeder hastily abandoned when I flicked on the yard light. But one summer, a flying squirrel came to stay and captivated me with its nightly waking ritual.
I found its home by accident, strolling past an old wooden bird house hanging on a cottonwood tree by a creek. Noticing twigs spilling out of the entry hole, I picked up a stick and absently poked it in. To my surprise, somebody inside grabbed it and pulled back! Hmmm. Probably not a bird. The red squirrels that inhabit our neighborhood are busy gathering food all day long and wouldn't be taking a mid-day nap. Must be a flying squirrel. I left it alone and resolved to return for a better look later.
That evening I took binoculars and sat in the bushes about twenty feet from the nest box. Nightfall in Montana comes late in early June, so I had to sit quietly and wait for quite a while. Eventually it got too dark for the binoculars to be of use, so I put them aside and peered through the dusk at the box. I was just about to give up and go inside when I noticed that the opening seemed to have changed shape. Its outline was getting larger and taking on an irregular shape. It was the squirrel, pushing his head and shoulders out to take a look around. By this time, I could hardly see at all, but I squinted and watched as he hung from the opening head-down for some moments, then twisted and climbed on to the roof of the nest box. He paused only a second or two, then scurried up the trunk of the cottonwood tree. Just when I lost sight of him in the branches, he launched and sailed to the base of a neighboring tree. He raced up that trunk and soared again, disappearing in the darkness.
I went back night after night to watch this performance. As the weeks passed, his emergence occurred later and later each evening. It got so I could look at the clock and the gathering dusk and predict to within two or three minutes when "my" flying squirrel would wake up to begin its nightly rounds.
The silent glide of a flying squirrel requires an elevated launching point - it cannot take off from the ground. The squirrel assumes a head-down position on a tree trunk, then pushes off with its strong hind legs, spreading all four legs to fully extend the gliding membranes. Once a squirrel is airborne, it makes course corrections by altering its wrist and foreleg positions. Its flattened tail acts like a rudder and adds to the lift provided by the flight membranes. Flying squirrels can make rapid side-to-side maneuvers, banked turns and tight downward spirals, as well as long-distance glides. But all good things must come to an end and eventually a glide runs out of momentum. The squirrel pulls upright at the last instant to land gently. In order to keep moving forward, it must climb again to launch a new glide. In winter, look for a characteristic landing patch, with tracks leading off in the snow.
Flying squirrels are omnivorous, eating lichens and fungi, buds, berries, seeds, insects, pollen cones of conifers, bird eggs and the occasional nestling. Much of their foraging is done on the ground, but they're also known for nightly visits to bird feeders."
(Broadcast: "Fieldnotes," 3/29/15. Listen weekly on the radio, Sundays at 12:55 p.m., or via podcast.)
