Predation

Predation is a relationship in which one organism, the predator, captures and feeds on another, the prey. Lions hunting zebras, spiders trapping flies and starfish prying open mussels are familiar cases. Ecologists group herbivory, the eating of plants, and parasitism with it as ways of consuming other organisms, but in the narrow sense predation means killing the prey, usually soon after it is caught.

Predation shapes both populations and evolution. The numbers of a predator and its prey can rise and fall in linked cycles, as in long fur-trapping records of lynx and snowshoe hares from Canada, where lynx numbers peak a year or two after the hares. By keeping herbivores in check, top predators can also protect the plants lower in the food chain, which is why many of them are keystone species. Over many generations, predators favor prey that escape and prey defenses favor better hunters. This evolutionary arms race has produced camouflage, warning colors, mimicry, spines, toxins, speed and keen senses on both sides.

Students meet predation in food webs, in predator and prey population graphs on exams, and in the Lotka-Volterra equations, a simple mathematical model of how the two populations affect each other.