Flying squirrels

Northern Flying SquirrelThe cat, Miss Jane, knows about flying squirrels. She eats some of those that winter in the wall of the house. My closest encounter occurred when I was proposing to clean out what I had thought of as a bird house. Nose-to nose-with an equally startled squirrel, I changed my assumption of occupancy and my plan. Miss Jane knows intimately certain aspects of squirrel behavior and physiology, but I’ve begun reading.

I’ve learned that flying squirrels are extremely common, though we seldom see them due to their position on the night shift of squirreldom. There may be two species of flying squirrels here in Bradford. Northern flying squirrels prefer the conifers and southern flying squirrels take the mixed deciduous. Although similar in appearance, their habits vary somewhat.

A brief column doesn’t provide nearly enough space to describe the flying squirrels’ large, night-vision eyes which, like the eyes of all rodents, are set far apart for a broad field of vision. This gives the squirrels a better chance of evading the owls and Miss Jane, but poor depth perception. Appearing wracked by indecision, they bob and weave nervously before leaping. In fact, they are triangulating, trying to get multiple visual angles on the proposed landing site. I regret not having enough space to describe why their eyes shine orange at night.

A single column offers barely enough space to include these facts about flying squirrels: They have very long whiskers, charmingly called “vibrissae.” They carefully notch an acorn to fit their small mouths before carrying it aloft to a cache hole in a tree, there to pound it in place with their incisors, producing a sound that might carry fifty feet. They roll their babies into balls to transport them from nest to nest, which they do frequently. They have a large vocal repertoire. Our northern flying squirrels grow fur on the soles of their feet in winter. Less territorial than other rodents, they aggregate in numbers in house rafters and hollow trees in winter for communal warmth and Olympic games.

All squirrels are fairly adept at falling out of trees unharmed. The principle is simple—stick your arms, legs and tail out to provide as much surface area and control as possible then hope for the best. Flying squirrels have taken this elementary parachuting a good bit further and possess a singularly wonderful body part known as a pataguim. This is the furry vestment that drapes from wrist to ankle on each side of the flying squirrel’s body.

No mere flap of extra skin, the pataguim contains a complex arrangement of muscles. Thin, flat muscles lie within the gliding skin and serve to control the direction of flight. Ropelike muscles along the outer edge hold the air foil taut. Additional muscles help stabilize the outstretched legs. They don’t “flap their wings.” Yet another set of muscles holds the pataguim close to the squirrel’s side so as not to impede them when they scamper afoot.

An added feature is a cartilaginous rod that extends from the wrist in flight to further open the leading edge of the gliding surface. At rest, the rod lies flat along the forearm. Imagine a stiletto knife that appears at the touch of a cufflink in some dreadful movie.

With all this specialized equipment in place, a flying squirrel glides silently through the night woods, spiraling down or making right angle turns as necessary. The initial powerful leap is usually followed by a short, step dive to gain velocity for glides of 20-60 feet on average. Glides of 150 feet are not unheard of, and down-slope distances of 300 feet have been recorded.

A flying squirrel may pancake to the ground to forage on nuts, seeds, and insects, or abruptly swoop upwards at the end of a glide to land on another tree. Its patagium billows to reduce speed, its tail wings upwards, its landing gear thrusts forward. After scaling this tree, it may leap again, speeding through the night forest.

One final note: a mother flying squirrel lies balanced on forehead and feet over her blind, naked offspring and spreads her furry pataguim like a blanket to keep them warm. Sounds delightful on a 10-below night.

By J. Ann Eldridge, UNH Cooperative Extension Wildlife Coverts Cooperator