concept

Optimal foraging theory

The idea that natural selection favours individuals who maximise net energy gained per unit of foraging time - so a predator should pursue a prey type only when the energy it expects to gain outruns the energy spent finding and catching it. When preferred prey is plentiful the hunter is choosy and ignores poorer targets; when it grows scarce the hunter widens its diet. This is no metaphor: predators really do behave, on the whole, as if running the sums, and that selfish accounting at the individual level becomes, for the whole forest, a mechanism that keeps it in balance.