By Steve Roark
Volunteer, Cumberland Gap National Historical Park

In 1936, ecologist Joseph Grinnell asked how oak trees could colonize the tops of hills and ridges. Acorns are too heavy to be dispersed by wind, and gravity tends to carry them downhill rather than uphill. He concluded that animals must be responsible for transporting acorns to higher elevations.

Many animals rely on acorns as a valuable winter food source. Deer, turkeys, wild pigs and bears consume large quantities, but an eaten acorn cannot germinate and grow into a tree. Some members of the squirrel family, such as chipmunks and flying squirrels, store acorns for later consumption. However, they typically store them in tree cavities and underground burrows, where the seeds cannot successfully germinate and grow. Tree squirrels, such as our own gray and fox squirrels, bury acorns just beneath the leaf litter, giving the seeds an opportunity to germinate and grow away from the parent tree.

Squirrels do not hibernate, so they must store large quantities of food to sustain them through the winter. Acorns are particularly appealing because they provide plenty of calories and are easier to open than hickory nuts or walnuts.

Not all acorns are alike, and squirrels treat each type differently. There are two major groups of oaks: red oaks and white oaks. Red oak acorns are rich in fat but contain substantial amounts of tannic acid, which makes them bitter. White oak acorns contain less fat but have much lower tannin levels, making them better-tasting. The two groups also differ in how their acorns germinate. Red oak acorns remain dormant during the winter and sprout the following spring, while white oak acorns usually begin to germinate soon after falling to the ground in autumn.

It is a common misconception that squirrels prefer the better-tasting white oak acorns. However, research shows that when given a choice, squirrels often select the higher-fat red oak acorns. They also tend to store more red oak acorns for winter and eat more white oak acorns soon after finding them in the fall. This is probably because white oak acorns lose some of their nutritional value once they begin to germinate.

Based on this behavior, it appears that squirrels have considerable influence over the spread of various oak species, particularly favoring the dispersal of red oaks. Unknowingly, they practice the art of forestry, influencing the growth and development of oak forests throughout the eastern United States. Considering the value of oak wood to humans, we owe these industrious little foresters our gratitude.