The following article was written by Woodcock Nature Center Educator Jen Meikle.
During fall, one of our afterschool activities is handing each child a basket and telling them that we’re going on a hunt to collect acorns. The kids always have such a great time searching the ground and filling their baskets, excitedly exclaiming and showing us how many they have found, the biggest and smallest ones, the special ones that are joined onto others, and so on. Once the acorn hunt is finished, they often beg to do it again and again, even when we have moved on to other interesting topics and activities!
Foraging is a human instinct and in the past and present in some areas, people would rely heavily on gathering their own nuts and seeds to help get through the winter, especially acorns. Acorns have been a staple to diets worldwide, including some Native American peoples. Acorns themselves are edible to humans, but contain tannins, which make them taste bitter and toxic to eat while raw. Through processing, which includes soaking them in water over and over until the tannins leach out, we can eat the acorns as nuts, make flour with them for baking, and even make acorn coffee!
Acorns are considered the most important form of mast in the eastern deciduous forest. (Mast refers to the edible fruit of woody plants. This includes many tree fruits we are familiar with, like maple seeds, beechnuts and hickory nuts.) Many animals rely on acorns as a major food source. Acorns contain large amounts of protein, carbohydrates and fats, as well as minerals (phosphorus, calcium, potassium and vitamin niacin). Black bears, white tailed deer, raccoons, eastern grey squirrels, mice, wild turkeys, wood ducks and blue jays all consume acorns, and they make up 25-50% of their fall diets.
When people think of acorns getting dispersed during fall, squirrels usually come to mind. Squirrels play a big role in helping seeds move away from their parent trees. They carry acorns up to 100 feet from their source. Acorns are buried by squirrels in an attempt to save food for later, called scatterhoarding. There is now strong evidence that squirrels actually remember where a majority of their caches are using spatial information, and often return to their caches. However, a lot of the time the acorns hidden end up germinating anyway, if there is an excess of food or the squirrel dies or relocates away from its caching area.
There is another animal that you may not think of right away, but that has an even larger impact on how acorns move around. Oak trees have a dispersal rate of one to two miles a year, thanks to squirrels, but also thanks to the blue jay. This time of year is also when blue jays start caching food to eat in winter and early spring. Blue jays are known to collect more than half of acorns produced in an oak stand and bury them up to one mile away! They can individually bury up to 4,500 acorns a year, and they only retrieve about one quarter of them for consumption.
During our acorn hunts with the children, perfect specimens are quite sought after. A round, unblemished acorn that is still sporting its cap is often the crown jewel of each child’s collection.
While we do find a good number of these, there is also a lot to be learned and appreciated by looking at acorns that appear to have been crushed, pecked at, or nibbled on! You can tell a lot about what kind of animal was enjoying an acorn meal by the condition of it.
- Mice almost always nibble a small hole by the top of the acorn and they end up leaving about half of the acorn meat behind; you can even see the tiny teeth marks if you look closely!
- The eastern grey squirrel and other rodents usually peel the outer shell of the acorn away in strips. Squirrels and chipmunks also usually end up leaving piles of acorns and other nuts on exposed rock as they eat; these are called middens. You can differentiate between grey squirrel- (largest), red squirrel- and chipmunk-eaten acorns (smallest) by the size of the peelings.
- Acorns that are chewed on by deer have a very ragged appearance because they pick up a bunch in their mouths at once and chow down, crushing them between their flat teeth and inevitably mangled pieces fly out! The surrounding area where a deer or wild turkey was searching for acorns to munch on will usually leave physical evidence as well as they claw at the ground, leaving exposed dirt and overturned leaves.
- Wild turkeys swallow acorns whole, letting their gizzards do the hard work. A turkey’s gizzard squeezes with twice the force of our own jaws, grinding up acorns and hickory nuts over time.
- Other birds besides blue jays also enjoy acorn meals; some common ones are the black-capped chickadee, white breasted nuthatch and the common grackle. Acorns make up 10-25% of the grackles’ diet. They have a hard ridge in their upper mandible that is perfect for grabbing the acorn and cutting a groove in the outer shell as they rotate it in their bill. This allows them to crack it in half to get at the meat.
- There is even a creature that relies on the acorn as first its birthplace and later its food source! If you find an acorn that looks untouched aside from a tiny perfect hole, it was the result of the larval stage of an acorn weevil burrowing its way out into the dirt below. An adult female acorn weevil lays her fertilized egg in an unripe green acorn, where the larva hatches and consumes the acorn from the inside until the nut ripens and falls. The weevil larva then burrows free and down into the ground, where it stays safe in the soil all winter long (or up to one to two years!), until it is ready to become an adult and repeat the cycle all over again.
Only one out of 10,000 acorns grows into a mature tree. If the acorn sprouts and makes it to adulthood, the resulting oak can take anywhere from 15 to 50 years to start producing its own acorns, depending on the species. Between 80 and 120 years is when acorn production is at its peak. Even though the odds of one acorn turning into an aged oak tree are slim, those that make it become crucial parts of the surrounding food web, giving life to over 100 different wildlife species, from tiny weevils to white-tailed deer.