Plants seem to be at the mercy of the animals that eat them. But roses and blackberries protect themselves with thorns. Milkweeds produce toxins that poison all but monarch butterfly caterpillars. And in the tropics, some acacias "permit" ants to live inside their thorns and drink their nectar. In return, the ants attack anything that so much as brushes against the tree.

So it should come as no surprise that some oaks wage war against gray squirrels. After all, who hasn't seen squirrels busily collecting and hiding acorns on the forest floor?

White oaks, it turns out, are not content to allow their fate to be determined by the ability of gray squirrels to recall where they buried their acorns.

Unlike red oaks, which delay germination until spring, white oak acorns germinate shortly after falling to the ground. Within a matter of days, white oak acorns send a tap root into the soil. In the process, most of the acorn's energy and biomass is transferred from the acorn to the root. The new taproot is of little interest to gray squirrels, so the seedling is safe, at least from gray squirrels.

But gray squirrels are not idle spectators to this ecological gambit. When gray squirrels handle white oak acorns, they somehow (perhaps by smell, taste or feel) distinguish them from other species of acorns. They bite into the acorn and remove its embryo. This kills the acorn so it cannot germinate, but the rest of the nut remains edible until the squirrels retrieves it later during the winter.

Fortunately, this tactic is less than perfect. If gray squirrels destroyed every white oak acorn, the tree would eventually vanish from the woods. But this is a learned behavior. Young squirrels miss many acorns, and even adults cannot find them all. So there are always white oak acorns that escape and germinate.

The beauty of such attacks and counterattacks by all predators and prey is that neither side always wins. Nature requires effectiveness, not perfection. Adaptive behaviors must work only often enough to ensure that predators and prey achieve life's ultimate goal -- successful reproduction.

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