Wildlife: Oak trees and acorns are vital to food chain
Share with others:
Bears, deer, squirrels, turkeys, wood ducks, mallards, chipmunks, deer mice, raccoons, ruffed grouse, woodpeckers, nuthatches and blue jays share a favorite food -- acorns. That makes acorns a keystone food in the eastern deciduous forest.
Although oaks do not produce bumper crops of acorns every year, the great diversity of oak species reduces wildlife dependence on a single oak species.
Worldwide, approximately 400 species of oaks have been described. North America hosts 90 species. Here in Southwest Pennsylvania, at least 11 species can be found. The most common local species include white, red, black, burr, scarlet and pin oaks.
Thanks to oak species 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 eat other foods, move or starve.
This year should be a good mast crop based on game forecasts on the Game Commission website. Wildlife Conservation Officers report prospects for squirrel hunting range from good to excellent throughout southwestern Pennsylvania.
Many people recognize oaks on sight by leaf shape -- large, leathery, broad and lobed. But the shape of oak leaves is as diverse as the variety of species. Many southeastern live oak species, for example, have long linear leaves with smooth margins. Locally. chestnut and chinkapin oaks leaves lack lobes. Chestnut oak leaves are large and trimmed with rounded teeth. Chinkapin oak leaves are smaller and trimmed with jagged teeth.
Most North American oaks can be grouped into two groups. The red oak group has leaves with sharp tips on pointed lobes, longer pointed buds and acorns that mature after their second growing season. Red oak acorns sprout the following spring. The white oak group has leaves with rounded lobes, short blunt buds and acorns that mature in the fall after one growing season. Furthermore, all oaks have multiple terminal buds and produce acorns -- nuts with distinctive caps.
Although acorn production of both red and white oak groups is predictable, it is not dependable. Some years produce bumper acorn crops, while other years the pickings can be slim. Biologists call this seed production strategy "predator satiation." Big crops satisfy all the seed eaters so at least some nuts escape predation and eventually germinate. Lean years keep nut-eater populations low so that even when food is abundant, there are too few nut-eaters to consume the entire crop.
First Published October 17, 2010 12:00 am
