Concept of conservation: Oaks and Acorns

The concept of conservation, using resources sustainably over time, is relatively new.

Early on we learned that even super abundant renewable resources can be depleted. In fact, the extinction of passenger pigeons just 100 years ago and the near extinction of bison in the 1800s led directly to a bio-ethic championed by early conservationists such as President Theodore Roosevelt and Aldo Leopold.

We learned that even uncountable species could be harvested to extinction. We also learned that plants are equally vulnerable.

Chestnuts once dominated the eastern deciduous forest and were the primary food source for most forest wildlife species. But thanks to a devastating fungal blight, chestnuts almost vanished in the blink of an ecological eye. Fortunately, another group of species filled the void.

New food source

Oaks and their acorns became the new keystone food for wildlife. Bears, deer, squirrels, turkeys, wood ducks, mallards, chipmunks, deer mice, raccoons, ruffed grouse, woodpeckers, nuthatches, blue jays, and myriad invertebrates rely on acorns.

Furthermore, many early human cultures learned to use acorn flour. In fact, if the global distributions of oaks and people are compared, the coincidence is striking.

People have used oaks for food, and perhaps more importantly, for building materials and fuel for thousands of years.

Worldwide, approximately 400 species of oaks have been described. North America hosts 90 species.

Eastern species

The most common eastern species include white, red, black, scarlet, pin, and burr oaks. Though oaks do not produce bumper crops of acorns every year, the diversity of oaks reduces wildlife dependence on a single oak species.

Thanks to oak diversity, there is almost always at least one species that produces a large fall crop of acorns.

In years when all oaks fail to produce much of a crop, wildlife suffers. They either find other foods, move, or starve.

North American oaks

Most North American oaks can be lumped into two groups.

The white oak group has leaves with rounded lobes, short blunt buds, and nuts that mature and germinate in the fall after one growing season.

The red oak group has leaves with sharp tips on pointed lobes, longer pointed buds, and nuts that mature after their second growing season. Red oak acorns sprout the spring after they fall. Furthermore, all oaks have multiple terminal buds and produce acorns — the familiar nuts with distinctive caps.

Clever approach

Gray squirrels, using senses of smell and/or taste, treat white oak and red oak acorns differently.

White oak acorns germinate shortly after they fall. By transferring energy from the nut to a rapidly growing taproot, many white oak acorns escape the jaws of hungry squirrels.

Gray squirrels counter with an ingenious learned behavior. When a squirrel collects a white oak acorn, it notches the shell with its incisors and removes the embryo. This makes the nut incapable of germinating, but it retains most of its nutritious meat for the squirrel.

Red oak acorns don’t mature until their second year; they germinate in the spring after they fall to the ground. By collecting and storing nuts throughout the woods, gray squirrels not only insure a winter food supply, they also scatter acorns because they never recover them all.

Undependable crop

Unfortunately, acorn production is not dependable. Some years produce bumper acorn crops, while other times production can approach zero. Biologists call this seed production strategy “predator satiation.”

Bumper crops produce enough acorns to satisfy all seed eaters with some left over so at least some nuts escape predation and eventually germinate. Well fed squirrels usually produce two litters, one in early spring and another in late summer.

Lean years, on the other hand, limit nut-eater populations. In years after a poor mast crop, for example, squirrels produce only one, if any, litter.

Vigilant effort

Successful conservation requires vigilance. That’s why we limit harvests of wildlife and timber and monitor the health and status of living resources.
Each generation should leave for the next a healthier natural world.

Of note: deer, squirrels, turkeys, woodpeckers, nuthatches, and jays love acorns, so they make an ideal addition to any backyard feeding station. One source is Vermont-based Acorno Acorns (www.acorno.com; 802-363-1582) where 10 pounds of acorns sell for $30 (60 to 80 acorns per pound) plus shipping.