A predator in ecology is any organism that kills and consumes other living organisms, called its prey, as a primary source of food. This interaction, called predation, is a key process that shapes populations, food webs and the evolution of species within ecosystems. Predation typically involves the predator locating, attacking, and often killing its prey before eating all or part of it.
Predators are widespread in nature, from animals to plants and microbes. Among animals, well-known examples include wolves hunting deer, lions pursuing zebras, and spiders trapping insects in webs. Some fish, such as sharks, stalk schools of smaller fish, while birds of prey, such as hawks and owls, capture rodents and other small animals using their specialized speed and vision.
Predators influence their prey both immediately and over evolutionary time. Prey often become more alert, flee sooner, or change when and where they feed to avoid being caught, essentially trading food for safety. Across generations, this pressure drives prey to evolve stronger defenses (such as armor, spines, toxins and sharper senses), while predators in turn evolve such traits as greater speed, stealth, or resistance to those defenses. This reciprocal adaptation, referred to as an evolutionary "arms race" or "coevolution," continually reshapes both populations.
Predator-prey interactions can also cause population cycles, with prey numbers usually dropping before predator numbers follow. In fast-reproducing organisms such as plankton or microbes, evolutionary changes can occur within just a few generations. Laboratory studies have even observed prey developing new defenses, such as less edible cell shapes, that reduce predator growth in only weeks.
Carnivorous plants, including Venus flytraps and pitcher plants, are also predators because they trap, kill and digest small animals, usually insects, to obtain nutrients not readily available from the from poor soils where they commonly live. Many non-carnivorous plants benefit indirectly from predators by attracting carnivorous animals that consume herbivores feeding on them. For instance, some plants release chemicals or nectar to attract ants or predatory insects that attack herbivores.
Although predators and parasites both exploit other organisms, they differ fundamentally in timing and effect. Parasites live in or on a host and typically keep it alive while feeding on it but often while reducing the host's health, growth or reproduction. Predators, by contrast, kill and consume other organisms quickly, often many over their lifetime. Parasites are usually smaller than their hosts and specialized for one species, whereas predators are often larger and hunt a variety of prey.