Tuesday, September 29, 2009
grasshoppers that have to take measures to avoid spiders grow more slowly and lay fewer eggs than grasshoppers in spider-free zones. In areas of Yellowstone where wolves are abundant, female elk give birth to fewer young. Birds that perceive their breeding area to be full of animals that will eat their eggs or young may skip breeding altogether, or lay fewer eggs than usual. In other words, predators keep prey numbers down simply by being scary.
But aren't there many more examples where the opposite is true - where predation urges growth? Where - even more counter-intuitively - predator and prey are cooperating on some level? As my teacher Michael Pollan elegantly demonstrated in Botany of Desire, predator prey relationships can turn into mutualism: The apple tree, rather than trying to poison its predator, instead pulls a kind of evolutionary judo move and uses the fact that it's being eaten to its benefit. Of course the apple did this by luck (the right configuration of genes at the right moment), but the fable of the apple seems useful in this recessionary world: When someone comes to eat you, the impulse is to react like the grasshopper - but if you can figure out a way to act like the apple, that looks like a far better strategy.