Diet

Although considered arboreal animals, flying squirrels do spend a small percentage of time on the ground, foraging for food such as fungi, insects and ground-level-fruiting berries. They also store nuts in shallow holes dug into the ground. It is at this time when they are most vulnerable to predation by land carnivores such as bobcat, coyote, wolf, house cat, etc.

Most foraging is done in the relative safety of the trees and shrubs in the animals' home range. Ground foraging is performed within "safe scamper distance" from a tree trunk. Males generally have a larger home range than females, however, any home range, where foraging is concerned, is dependent upon available food supplies. If there is a paucity of food in any given area, a flying squirrels' range will be increased. The reverse is true if there is an abundance of food at hand.

Flying squirrels, as a rule, are scatter-hoarders, although southern flying squirrels have been known to stash large quantities of beech nuts in "larder cavities" (large natural cavities in trees). Northern flying squirrels are much less likely to larder hoard. In fact, there is no documentation regarding larder hoarding activity in northerns. Flying squirrels, once they have located a food item, will either eat it right on the spot, or find a suitable location to store it, for, it is hoped, retrieval at a later time. Areas where a flying squirrel may store its' find can be notches and crevices in tree branches, natural cavities, shallow digs under the forest floor leaf litter, and under logs. They will press the food into the storage spot by banging it down with their incisors. Depending upon location and time of year, one can often hear the rapid "bonk bonk bonk bonk bonk" sound of hard mast being stashed by a flying squirrel on a windless night in the forest. Sometimes they will "finish off" the storing ritual with a few pats of the forepaws.

*Note - red squirrels are great examples of larder hoarders. These squirrels store huge amounts of cone crop in underground middens. Some excavated middens have produced enough stored cone crop to fill an average-size garage!. Flying squirrels are not partial to cone samaras, as was once believed.

Of course, there is nothing to stop the dirunal red squirrel from locating and eating or stashing what the nocturnal flying squirrel had stored the night before, and vice versa, although flying squirrels will not normally venture into a red squirrel's middens. But red squirrels will hide food items at height too. And red squirrels have a neat method of air-drying the above-ground fruiting mushrooms they like to eat. They will cut the top off a mushroom, run up into the trees, find a broken twig on a limb and "spike" the mushroom cap onto the broken twig. This mushroom cap will be left there to air dry, for retrieval by the squirrel at a later date! Or a flying squirrel will snag it on one of its' nightly forays. Regardless, nothing is wasted!

How does a flying squirrel open a hard mast item like a hickory nut? You would think those tiny incisors would be no match for a rock-hard shell of a hickory nut, but you would be wrong! And flying squirrels have a unique method of opening hard mast nuts...so unique, in fact, that one can determine a flying squirrels' presence in a woodlot by examining spent nut meat shells found on the forest floor! Have a look at the shagbark hickory nuts pictured below.

These shagbark hickory nuts have been opened by a flying squirrel. Note how each nut is opened in the same manner. One opening only, the cut is smooth with no jagged edges anywhere. The shape is ovoid (oval, or egg-shaped).

Only flying squirrels open nuts this way. Peromyscus spp. (i.e. deer mouse and white-footed mouse) create several smaller, irregular-shaped holes to get at the nutmeat. Red squirrels create rough-edged, irregular-shaped holes, and grey squirrels just rip the nut to pieces.

Flying squirrels have very small mouths. How do they grab on to large, hard, smooth and round objects? Simple! First, they'll cut, say, an acorn from it's branchlet. Then they will hold the nut in their forepaws, determining, probably by weight, whether the nut is "good" or whether it has been attacked by a moth larvae. The squirrel may then rotate the acorn around and around, scraping the outside with its incisors, perhaps determing by sound quality whether the nut is indeed "good". If it passes the test, our hungry squirrel will then cut notches into the skin of the acorn so that it may bite into it strongly enough to either carry off, or glide away with, the prize in its mouth. If the acorn has a moth larvae inside, rather than drop it to the ground dismissively, a flying squirrel may simply open it on the spot and chow down on the larvae!

Flying squirrels will bring food into their nests, although not normally will lactating mothers bring food into the natal nest. Flying squirrels will eat "out in the open" or within the relative safety of a refuge nest, or what we call a "cafetorium".

Dr. Illar Muul found that flying squirrels mark every "storable" piece of food (i.e. acorn, hickory nut) with chemicals exuded from enlarged sweat and oil glands found in their lips. Muul postulated this enables a squirrel to discern whether or not a particular nut has been stored or handled, thereby reducing the unnecessary energy expenditure that would be required to re-store an already marked item. In an experiment, nuts taken from a feeding station and stored by a flying squirrel were retreived and returned to the feeding station. The flying squirrel subsequently ignored those returned nuts, as in the squirrels' mind, they were already stored!

From his studies of hoarding behaviour in southern flying squirrels, Muul also suggested that one squirrel could, given the proper conditions, store as many as 15,000 nuts in a season!

How does a flying squirrel know when to start hoarding nuts? Dr. Muul performed work on flying squirrels and their circadian rhythms and found that changing photoperiods, or daily amounts of light, determined when the squirrels began their frenzied nut-stashing. He kept a colony of flying squirrels indoors, and found that by increasing or decreasing the amount of light they received, their hoarding activity followed suit. Less light made for more hoarding activity. More light made for less hoarding activity. In the wild, a flying squirrel subconsciously registers the lessening amount of light each day, which in turn subconsciously tells the squirrel that winter is on its way.