Predation

Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the host) and parasitoidism (which always does, eventually). It is distinct from scavenging on dead prey, though many predators also scavenge; it overlaps with herbivory, as seed predators and destructive frugivores are predators.

Predation behaviour varies significantly depending on the organism. Many predators, especially carnivores, have evolved distinct hunting strategies. Pursuit predation involves the active search for and pursuit of prey, whilst ambush predators instead wait for prey to present an opportunity for capture, and often use stealth or aggressive mimicry. Other predators are opportunistic or omnivorous and only practice predation occasionally.

Most obligate carnivores are specialized for hunting. They may have acute senses such as vision, hearing, or smell for prey detection. Many predatory animals have sharp claws or jaws to grip, kill, and cut up their prey. Physical strength is usually necessary for large carnivores such as big cats to kill larger prey. Other adaptations include stealth, endurance, intelligence, social behaviour, and aggressive mimicry that improve hunting efficiency.

Predation has a powerful selective effect on prey, and the prey develops anti-predator adaptations such as warning coloration, alarm calls and other signals, camouflage, mimicry of well-defended species, and defensive spines and chemicals. Sometimes predator and prey find themselves in an evolutionary arms race, a cycle of adaptations and counter-adaptations. Predation has been a major driver of evolution since at least the Cambrian period.

At the most basic level, predators kill and eat other organisms. However, the concept of predation is broad, defined differently in different contexts, and includes a wide variety of feeding methods; moreover, some relationships that result in the prey's death are not necessarily called predation. A parasitoid, such as an ichneumon wasp, lays its eggs in or on its host; the eggs hatch into larvae, which eat the host, and it inevitably dies. Zoologists generally call this a form of parasitism, though conventionally parasites are thought not to kill their hosts. A predator can be defined to differ from a parasitoid in that it has many prey, captured over its lifetime, where a parasitoid's larva has just one, or at least has its food supply provisioned for it on just one occasion.

There are other difficult and borderline cases. Micropredators are small animals that, like predators, feed entirely on other organisms; they include fleas and mosquitoes that consume blood from living animals, and aphids that consume sap from living plants. However, since they typically do not kill their hosts, they are now often thought of as parasites. Animals that graze on phytoplankton or mats of microbes are predators, as they consume and kill their food organisms, while herbivores that browse leaves are not, as their food plants usually survive the assault. When animals eat seeds (seed predation or granivory) or eggs (egg predation), they are consuming entire living organisms, which by definition makes them predators.

Scavengers, organisms that only eat organisms found already dead, are not predators, but many predators such as the jackal and the hyena scavenge when the opportunity arises. Among invertebrates, social wasps such as yellowjackets are both hunters and scavengers of other insects.

While examples of predators among mammals and birds are well known, predators can be found in a broad range of taxa including arthropods. They are common among insects, including mantids, dragonflies, lacewings and scorpionflies. In some species such as the alderfly, only the larvae are predatory (the adults do not eat). Spiders are predatory, as well as other terrestrial invertebrates such as scorpions; centipedes; some mites, snails and slugs; nematodes; and planarian worms. In marine environments, most cnidarians (e.g., jellyfish, hydroids), ctenophora (comb jellies), echinoderms (e.g., sea stars, sea urchins, sand dollars, and sea cucumbers) and flatworms are predatory. Among crustaceans, lobsters, crabs, shrimps and barnacles are predators, and in turn crustaceans are preyed on by nearly all cephalopods (including octopuses, squid and cuttlefish).