Going Nuts for Acorns
The autumn attack of oak trees is upon us, as acorns plummet with a thud on rooftops, cars and … our heads. Winter is approaching, and animals will begin hoarding this valuable food resource. Employing one of two strategies, they either will construct a central food cache or larder that they vigorously defend, or many different food caches, usually with a single food item, by scatter-hoarding.
According to the University of Georgia’s School of Forestry, more than 20 species of oak trees are native to Georgia. With the genus further subdivided into red and white oak categories, white oaks generally produce leaves with rounded lobes and include species such as live, post and overcup. Red oaks, which include water, black and turkey, generally have leaves with pointed lobes. Besides the shape of their leaves, their acorns also exhibit differences.
A single oak tree can produce thousands of acorns in one season. From these large seeds, mighty trees can grow. White oak acorns tend to be long and narrow; red oak acorns are fat and round. White oak acorns also have a crown or cap that covers about one-quarter of the body. In contrast, red oak acorn caps are nearly flat on top.
Being relatively high in carbohydrates, acorns are a significantly concentrated source of energy. Yet, not all acorns are not the same in terms of nutritional content or tastiness.
White oak acorns generally are more palatable to animals, such as deer, opossums, raccoons, foxes and turkeys, than red oak acorns, because they contain fewer tannins, which are bitter-tasting chemicals that function to protect the acorn from insects and animals. Although acorns from red oaks tend to be higher in fat, protein, calories and fiber than acorns from white oaks, the astringent quality (what causes you to pucker when you eat unripe fruit) of the red makes them less tasty.
However, many species will eat both types, especially during late winter into early spring, when the white oak varieties are gone. In fact, a 1998 University of Richmond study found squirrels eat 85% of white oak acorns shortly after discovery, and scatter-hoard 60% of the red oak acorns. White oak acorns usually germinate in the fall, shortly after falling from the tree, and they quickly lose their nutritional value if stored for an extended period in the ground. Therefore, more than half of its stored energy goes to the seedling and not the squirrel.
Another observation researchers have made is what a squirrel does when it first picks up an acorn … it rolls and shakes it. Scientists did not realize this was happening until they watched slow-motion video of squirrel behavior. They shake the acorn to assess the seed quality, as many acorns can be filled with weevils and other insects. If insects are present, the squirrel will eat the acorn and weevils right away. If it is free of insects, it might choose to hoard it for later. Additionally, squirrels have been known to pry off the caps of red oak acorns, bite through the shells to get the nutritious inner nut meat, and then discard them half-eaten with the embryo (baby plant) still intact. Because the embryos are not destroyed, the damaged red oak acorns still can germinate.
But, what happens if a squirrel forgets where it has hidden an acorn? Eventually, it might sprout a new tree. Not only is a squirrel’s taste for acorns essential for its own nutrition and survival, but it also is essential for the regeneration of oak forests.
– Karen Garland has been a Cherokee County Extension volunteer and Master Gardener for more than 20 years. She is a teacher in the Cherokee County school system.
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