Arms Race
Here we are again dealing with an arms race, this time between ani- mals such as ourselves, who eat plants, and the plants, which need to protect themselves from being eaten. When Stone Age inhabitants of central Europe died of starvation late one winter instead of happily filling up on oak buds and acorns, they were losers in the contest with oak trees. Oak buds and acorns are loaded with nutrients, but, unfor- tunately for potential consumers, they are also loaded with tannins, alkaloids, and other defensive toxins. Early Europeans who filled up on unprocessed oak tissues died even sooner than their starving com- panions did.
Animals that eat other animals may have to deal with venoms or other harmful materials manufactured by their prey, and they will certainly have to deal with at least traces of the plant toxins eaten by the prey. The monarch butterfly caterpillar, mentioned earlier, feeds on milkweed not only because it has machinery that makes it invul- nerable to the milkweed’s deadly cardiac glycosides but also because it becomes poisonous itself by consuming the plant and is therefore avoided by potential predators. Many insects and arthropods protect themselves with venoms and poisons. Many amphibians are poison- ous, especially the bright-colored frogs that Amazonian peoples use to poison their arrowheads. The vivid colors and patterns of such poisonous animals protect them from predators, who have learned from bitter experience that such prey are not pleasant food items. If you are starving in a rain forest, eat the camouflaged frog that is hid- ing in the vegetation, not the bright one sitting resplendent on a nearby branch.
