Much to my amazement, when I turned to Kathleen Kudlinski’s “The Naturalist” column on Sunday, I found that what I witnessed in the Maine woods this September has a name: Acorn Rain.
Plunk! Plop! Gee whiz! Some acorn season this is!
Last year our oaks made only a handful of acorns on each tree. This year, the sound of acorns falling punctuates our lives 24/7. Acorns crunch underfoot with every step down our stone path, the grass looks beaten down, and the dog has given up lying in the yard. It is too dangerous. Plop! Thunk! Yelp!
When a tree produces a ridiculously abundant crop of nuts, it is called a “mast” year. One tall mature oak tree can produce almost 1,000 pounds of acorns in one growing season during normal weather conditions. Pines, oaks, chestnuts, spruce, walnuts, beech — all operate on the bounty-or-bust system. But why?
Predator saturation. Most of us think of predators as animals such as coyotes, fishers or hawks. They chase and eat other animals for a living. From an oak tree’s point of view, gray squirrels are predators, too. In their scenario, squirrels are vicious monsters who scurry after and eat every baby oak tree (read: acorn) they can find. That’s why, for most years, only a few acorns are produced.
Many acorns are snatched from the tree by those nasty squirrels or vicious, predatory birds like blue jays before they fall. Only a few acorns hit the ground under the trees. Ferocious turkeys, sap-thirsty mice and cruel deer snap up the rest. Populations of these “seed predators” are more or less in balance with an average year of nuts.
But 2010 is no average year. There are just not enough animals to eat all the acorns during a mast year, when acorns lie ankle-deep under most trees. The situation ensures that many acorns live to get planted. Some have a chance to get started as seedlings.
Fallen acorns don’t just lie there, helpless. They’re encased in a tough seed coat, for starters. But there’s more: The seeds are poisoned. Many plants use chemical weapons that are repulsive to animals. Acorns come flavored with tannin, a bitter compound we use to tan hides.
Tanning a hide means soaking a soft, flexible, tender skin in tannins to produce shoe leather, among other things. Tea plants use tannin, too, to protect their leaves. In tiny amounts, it flavors your cup of tea. You and I, and all other animals, have a delicate and tender lining to our intestines through which we absorb dissolved food. Carbohydrates and other nutrients in food are not absorbed if a diet is high in tannins. Makes sense; your gut couldn’t sop up anything if its soft lining was tanned into shoe leather.
A few acorn predators have digestive systems that can handle tannins. Some even break them down into harmless chemicals. This chemical warfare has been waged for eons. The plants develop a defense; the animals adapt. The plants who come up with a new defense thrive — until their predators evolve again to overcome the problem.
Many animals let themselves go, and just gobble acorns in a mast year. Sure, they lose some nutrients because of the tannins, but they make up for it in the sheer volume of acorns eaten. So deer, squirrels, quail, jays and many other ferocious predators eat as many acorns as they can, often leaving them for a few weeks on the ground before they eat them. The resting period allows the seed coat to crack and some of the tannins to leech out. If you want to eat acorns, you, too, need to crack them open and soak or boil for a while. Acorn preparation is clearly explained at http://www.grandpappy.info/racorns.htm.
Pointy-leafed red oaks make the bitterest acorns. White oak acorns are the lowest in tannins and, from some trees, are almost sweet enough to nibble as they fall. You might decide to try one as they fall all around. It boils down to one question: Do you feel lucky? Plunk!
Kathleen Kudlinski’s “The Naturalist” column is a regular feature of the New Haven Register Sunday edition. This column was published on September 26, 2010 and I’ve reprinted it here with permission. Kathleen’s excellent blog is The Pondside Place at http://www.kathleenkudlinski.com/