Boundaries
by Jack Nisbet

Jack Nisbet is the author of The Mapmaker's Eye, Sources of the River, Purple Flat Top, Singing Grass, Burning Sage and Visible Bones. His newest, The Collector, won a 2010 PNBA Award.

Northern Flying Squirrels
February 2010

Some winters ago, I held the key to an old brick school building, so I could come in early before classes to catch up on work. One dark morning I slipped in through the side entrance and hopped up to the long hall that fronted all the classrooms, headed for my desk in the library. But instead of an empty corridor, I found myself face to face with a flying squirrel, not much larger than a mouse, sitting in the middle of the maple floor. It was the huge dark eyes and velvety fur that gave the little rodent away.

Thinking that the squirrel had somehow glided in behind me, and that it was in a terribly wrong place -- the kids would go out of their minds if they saw something like this -- I decided to pick it up, very gently, and put it back on a tree outside. The creature seemed frozen with disorientation, and two slow steps brought me directly above its tiny form. Nothing seemed easier than to lean down, pluck it very carefully from its spot, and release it back to the safety of darkness. I'd be sitting in the library before the door closed behind me.

Just as my hands wrapped around the little squirrel, however, it moved to one side. Only two bumps, nothing panicky. I straightened, took a single step down the hall, and bent toward it. The squirrel hopped another couple of yards away, so deliberately than I couldn't believe my smooth swipe missed its target. The twin dark oceans of those nighttime eyes still betrayed no sign of alarm. When I lurched for it again, the sharp claws clicked once on the shiny maple planks as it avoided another grasp without any extra fuss.

The hallway had to be half a football field in length, but we went all the way down it in exactly that manner. Me pausing, closing in, reaching down for a touch; the squirrel watching carefully in the dim light, moving only at the last instant, and then never more than a few feet. I finally cornered it at the far end, against the opposite side double doors. There it sat quietly while I squatted as wide as possible, curled my arms around as a curtain, and cupped its soft pliant fur in my palms. The squirrel bit me on the forefinger, hard.

I squawked involuntarily and dropped it back to the floor. It ran between my legs, up the three steps, and began to lope back down the long hall like a stop-motion cartoon: forepaws up; its glider skin stretching out like a cape from wrists to ankles until it engaged and then pulled the back paws along; flat tail spread like a rudder twisting this way and that to guide the awkward process. I could trot almost as fast as the squirrel's pace, but decided to choose my moment carefully before attempting another capture. I wanted to help this creature, not hurt it or myself any more than necessary.

As we wove our way along the corridor, I pulled a handkerchief from my pocket and calculated exactly how I would drape it over the squirrel in the corner by the original entryway. Everything looked set as my quarry passed the last classroom, hopped off the first of the three steps -- and vanished into thin air.

Mystified, I searched for ten minutes before lying down at the foot of the three stairs. On the second one, about halfway along the underside where the tread met the riser, my fingers touched a knothole that had been chewed out just enough to allow a little squirrel to squeeze through. It was only then that I realized that this flying squirrel probably didn't need any help from me.

With or without the knowledge of people, northern flying squirrels obviously do just fine in the forests of the North Columbia country. Intermediate in size between a chipmunk and our familiar red tree squirrel, they seldom draw attention because of their nocturnal habits. But tribal stories and place names clearly show that their world occasionally intersects with the human one, and old-time trappers, particularly of squirrel predators such as martin and fisher, described catching dozens of flying squirrels in traps meant for larger fur bearers. Perhaps that is the source of the odd designation of "Camp Flying Squirrel" at a site west of Fort Colvile on Hudson's Bay Company agent A. C. Anderson's early map of the region (See Boundaries column for March 2009).

Over the past few decades, researchers have been paying more and more attention to the role of flying squirrels in Northwest forests, and now consider the flying squirrel a crucial monitor of their overall condition. "A keystone species such as the flying squirrel is easy to define," says Andrew Carey, a research biologist for the Ecological Foundations of Biodiversity in Olympia. "It's a species that has a disproportionate influence on the ecosystem relative to its abundance within that ecosystem."

The reason for such elevated status is that flying squirrels and some of their relatives are experts at sniffing out truffles-- underground mushroom kin that fruit in the spring or fall and are technically known as ectomycorrhizal fungi, or EMF. Each truffle has its own particular scent, its own nutritive makeup, and a life history that involves attaching to the root tips of a specific tree system. These fungal attachments help the tree to absorb water and nutrients from the soil, and also to move photosynthetic carbohydrates back into the soil from the tree. As the nutrients allow the tree to thrive, the carbon supports the panorama of microbes, insects, nematodes, bacteria, and fungi in the soil.

Flying squirrels are supremely effective at finding truffles, scratching them out of the ground, and gobbling them up fast. As the squirrels then glide through the forest canopy, their random droppings redistribute the spores, yeasts, and bacteria from these truffles to colonize new trees.

Since truffles are relatively low in nutrition, it takes several different kinds of the underground fungi, combined with a wide variety of other forest foods, such as lichens, insect pupae, bark, and plant material, to keep a flying squirrel healthy. In much the same way, it takes a complex forest to provide such an array of possible food items, and keep them available across the patterns of season and climate. Thus the triad of squirrels, truffles, and trees make up what Andrew Carey terms a keystone complex.

While most of the studies on this special relationship have focused on douglas-fir forests west of the Cascades, a recent project on the east side revealed the same kind of richness in interior forests dominated by ponderosa pine. Over a period of four years, researchers collected fecal pellets from over 300 flying squirrels. The spores in those tiny poops came from 23 different species of fungi, plus a wide variety of other plant material. Spring collections yielded a dozen different kinds of truffles, while in the fall the number jumped to 19. No matter what kind of test plot was studied, the squirrels tended to consume about four times as much fungi as plant material. (For the full report see "Truffle abundance and mycophagy by northern flying squirrels in eastern Washington forests" in Forest and Ecology Management 200 [2004]: pp. 49-65).

It seems only natural that modern scientists would like to manage forest plots to produce more kinds of ectomycorrhizal fungi, in the hopes of leading to more complex, healthier forests. And it only natural that flying squirrels, who seem to know more about EMFs than anyone else, would be a species to monitor in the hopes that they might aid the process. But the researchers in the ponderosa pine project came to no firm conclusions as to what might constitute effective EMF management -- there are simply too many unknowns in the equation to make sense of it right now. As the squirrel in the school hallway proved, taking a walk with a flying squirrel is one thing; understanding exactly what it is up to can be quite another.

Illustration: scratchboard by Emily Nisbet

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