If you live near a stand of Red Oak trees, your chances of seeing a Porcupine this fall are greater than average. At the end of August, when the apple supply has dwindled, Porcupines move on to important new food sources – acorns and beechnuts. While American Beech trees in central Vermont have not produced a bumper crop of beechnuts this year, Red Oaks are experiencing a very heavy mast crop. These acorns provide sustenance for many animals – Black Bears, Red and Gray Squirrels, Eastern Chipmunks and other small rodents, White-tailed Deer and Wild Turkeys, to name a few.
Porcupines are typically one of the first acorn consumers, as they are able to climb oaks and eat the acorns before they drop and are accessible to many of the other animals that are limited to foraging on the ground. If you see the tips of branches nipped off with acorn caps (but no acorns) still attached lying under an oak tree, it’s likely that a Porcupine has been dining in the tree and discarding branches after scooping out and eating the acorns.If the tree is large, the Porcupine may reside in the canopy for several days. (Thanks to Emma for photo op.)
If you have oak trees in the woods near you, chances are great that their acorns attracted wildlife this past fall, one of which was most likely a Gray Squirrel. Unlike Black Bears, Wild Turkeys and White-tailed Deer, which eat acorns immediately upon finding them, Gray Squirrels tend to cache acorns for winter consumption. They do so by burying them individually, often in fairly close proximity to where they find them. (Red Squirrels also cache food in the fall, but typically bury numerous seeds, mostly conifers and maples, in one spot.) When food becomes scarce, as it usually does this time of year, it is possible to find numerous holes dug in the snow, frequently with leaves and bits of acorn shells littering the snow around them. Tell-tale Gray Squirrel tracks leading to and from these holes identify the excavator.
The method in which a nut has been opened depends on both the species of nut as well as the species of animal that opened it. To complicate things further, it can be difficult to ascertain who opened a nut as a given species, such as the Red Squirrel, often has more than one way of opening a nut. However, a given squirrel usually chooses one way to open a nut and consistently uses that method, so that if you come upon a pile, or midden, of nuts eaten by a Red Squirrel, the nuts will most likely all have been opened in the same way.
The beveled edges on the hole in the pictured Black Walnut, the fact that it was opened from both sides (leaving the dividing rib between the two sides intact), and the central location of the holes are indications that a Red Squirrel dined on the nutmeat. The chewing of open, jagged holes on either side of a nut is a Red Squirrel’s most common method of opening a nut. Gray Squirrels tend to remove the entire side of a walnut, as opposed to chewing a hole in it.
Bones, antlers, skulls, turtle shells – all are recycled relatively quickly by rodents seeking a source of minerals, particularly calcium and phosphorus. All rodents possess four incisors, two in the front of the upper jaw and two opposite these, on the bottom jaw. These incisors, unlike other teeth, never stop growing. By gnawing on hard objects such as bones, rodents keep their incisors paired down. If an incisor is broken or lost, the opposing incisor will continue growing in a circle, having nothing to grind against, causing the rodent to die of starvation or from having its brain pierced (through the roof of the rodent’s mouth) by the ever-growing incisor. In this photograph, a gray squirrel is obtaining minerals and sharpening its incisors on a moose skull that a human wedged into the crotch of a tree.
Many species of squirrels, including the red squirrel, are “larder hoarders.” Each individual stores its food in one central area that it defends aggressively against invaders. Eastern gray squirrels, however, are “scatter hoarders,” collecting and burying one nut at a time throughout home ranges up to 7 acres in size. It has been estimated that up to 25 percent of the nuts that gray squirrels cache are stolen by other gray squirrels. Researchers have found that gray squirrels engage in “deceptive caching.” Carrying a nut, a squirrel will repeatedly dig a hole and then fill it in, without depositing the nut. They also will cover a spot with leaves, even though they have not buried anything in this location. Where gray squirrel densities are high, the squirrels often keep a cache in its original location for only about three days before moving it to a new location.
In the fall, Eastern Gray Squirrels bury individual acorns from Red and White Oaks to sustain themselves through the winter. The acorns of Red Oaks have delayed germination – they can be stored up to six months before they start germinating. The acorns of White Oaks, however, have no such dormancy, and begin to germinate in the fall, soon after they fall from the tree. Once acorns sprout, they are less nutritious, as the seed tissue converts to the indigestible lignins that form the root. Gray Squirrels, as a means of “long-term cache management,” selectively remove the embryos from White Oak acorns (but not from Red Oak acorns) before burying them. Germination is prevented, and the storage viability of the White Oak acorns is extended by six months, equaling that of the Red Oak acorns.