Before I say anything about the importance of acorns in the forest, it’s important to start with the fact that the world’s biggest acorn is in Moore Square Park in downtown Raleigh. It’s fitting to find it there. After all, Raleigh calls itself “The City of Oaks.” And if it were real, there's no doubt this nut would produce a giant oak. The big nut is 10 feet tall and weighs about 1,250 lbs.
There are plenty of other, smaller acorns to be found on the ground all over the park. Oak trees begin producing nuts at about 20-years-old and there are plenty of mature, large trees in the park. That’s a good thing, because in an urban setting as well as deep in the forest, acorns play an important role in forest ecology because of what is on the inside.
The most important item inside the acorn, of course, is the makings of a new oak tree. In addition to the seed, the nut contains all of the food required if the acorn was in the woods and allowed to germinate. It would use the food until the seedling of a tree was able to grow enough of a root to get its own food.
All of that meat provides a substantial food source for birds, such as ducks and jays, as well as small and large mammals such as squirrels, mice, deer and bears. All of those creatures eat large amounts of acorns. In fact in the fall, as the acorns are dropping, acorns can make up to 25% of a large mammal's diet.
Biologists say the nuts are attractive to animals because they are large, which means a lot of food in one nut, and they are also easily cached. Acorns are also very nutritious: 50% carbs, 4% protein, 4% fat, and 34% water. If you’re an animal searching for food, acorns can take care of a lot of your nutrition needs.
If Mother Nature’s creatures are smart in eating acorns, they are also smart in what part of the acorn they don’t eat. Acorns contain bitter tannins. The amount of tannin varies with the species of acorns. There are about 450 species of oak trees around the world.
The tannins tend to be in the bottom half of the acorn, which is why you often see squirrels eat only the top half of the acorn. Squirrels will eat a white oak’s entire acorn because those are the least bitter. They will store the acorns from red and black oaks to not only have food for the winter but also in hopes at least some of the bitterness will leach into the soil.
There’s no doubt acorns are important to the forest. But it turns out squirrels aren’t dumb.
- Frank Graff
Frank Graff is a producer/reporter with UNC-TV, focusing on North Carolina Science Now, a weekly science series that airs Wednesdays, beginning in August 2013, as part of North Carolina Now on UNC-TV. In addition to producing these special segments, Frank will provide additional information related to his stories through this North Carolina Science Now Reporter's Blog!