When Squirrels Fly

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Critical Critters

Gliding prowess and nocturnal habits notwithstanding, flying squirrels are largely defenseless and hardly immune to hungry predators. Martens, weasels, foxes, raccoons, snakes, bobcats and hawks all take a toll. Owls, though, are by far their deadliest enemies. According to one estimate, a pair of northern spotted owls consume as many as 440 flying squirrels a year. In the Pacific Northwest, northern flying squirrels account for at least half of a spotted owl’s diet. Southern flying squirrels also are considered a critical food source for owls and other woodland wildlife in much of their range.

Even more important, many ecologists say, is the role flying squirrels play in the dispersal of spores of mycorrhizal fungi — various species of underground fungus, such as truffles, that not only serve as a major food source for the squirrels, but also maintain a vital symbiosis with forest trees. The subterranean fungi’s far-reaching threadlike roots, or hyphae, penetrate tree rootlets and transfer water, minerals and nutrients to host trees, in effect acting as an extension of the trees’ own root systems. Some mycorrhizal fungi also protect trees from disease pathogens.

When a flying squirrel consumes a truffle or other fungus, spores pass unharmed through the animal’s digestive tract, combining and fermenting with other ingredients in the animal’s diet, and come out compressed in pellets that contain not only spores, but also nitrogen-fixing bacteria and growth-stimulating yeast: forest food concentrate. More often than not, the pellets are conveniently deposited beneath trees, where they ensure the continued colonization of fungi and, as a result, longer life spans for their hosts.

In some forests, flying squirrels are so overwhelmingly important to this cycle, and so predominant as a food source to wildlife, that they’re considered a keystone species — without them, the local ecosystem would be drastically altered. In many areas, biologists now use flying squirrel populations as a measure of a woodland habitat’s overall health.

The secretive flying squirrel, it seems, is much like the roots beneath the trees it inhabits and nurtures: unseen and thus underappreciated by out-of-sight, out-of-mind humans, but nonetheless critical in nature’s grand scheme.

Getting a Glimpse

If you live within the range of either North American flying squirrel species and are willing to sacrifice a little sleep, you just might get lucky and catch a glimpse of one in your back yard. Here are some tips:

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