The behaviour by means of which an animal of one species, the predator, kills and eats a member of another species, the prey. The motivation for predatory behaviour is usually hunger, but this is not always so. In most animals, the speed and efficiency of prey capture increase with hunger, but in the praying mantis (Hierodula crassa) and the jumping spider (Epiblemum scenicum) the stereotyped movements of prey capture remain unaffected by hunger.
Many predatory species obtain food that they do not eat themselves, but give to their young. Usually, obtaining food for the young is under the control of stimuli from the young, rather than the hunger of the parents. Birds of many species adjust their parental foraging to the size of their brood. The begging behaviour of the young is the prime stimulus by means of which the parents adjust to their food requirements. The predatory behaviour itself may also be different when it is for the benefit of the young. Thus domestic cats (Felis catus) and cheetah (Acinonyx jubatus) usually kill their prey soon after capture, but when it is for the young they carry live prey to the litter and release it in the presence of the kittens. Some birds eat the food themselves and then regurgitate it to their young, while others select smaller prey items than those that they would eat themselves.
Many birds and mammals kill more than they eat and store the surplus. Ravens (Corvus corax) are more likely to store food when they are hungry, whereas shrikes (Lanius sp.) store more when they are satiated. Ravens store prey at the time that they are feeding their young. Thus ravens store in response to demand, whereas shrikes store in relation to the abundance of available prey. The relationship between hunger and hoarding is complex, differs from species to species, and serves different functions in different species.
Choice of prey is often dictated by availability, but many predators may concentrate on one prey and then suddenly switch to another. Thus redshank (Tringa totanus) when feeding upon the marine polychaete, Nereis sp., select large worms whenever possible and pass over small ones. If the shrimp Corophium spp. is available, these are taken preferentially, even though the redshank would gain much more energy by sticking to worms. This aspect of food selection is almost certainly related to the particular nutritional requirements of the predator.
Many predators have rhythms of predatory behaviour. These may be related to the availability of prey, or the rhythms may be endogenous, persisting independently of environmental factors. The northern shrike (Lanius excubitor) usually feeds upon insects and lizards, but in the autumn the lizard content of the diet drops to zero, even though the lizards remain plentiful. Many predators have a marked circadian rhythm. Thus domestic cats have a pattern of nocturnal hunting that is independent of their food supply, but matches the availability of their natural prey.
Predators obtain their prey by foraging, which may include searching and hunting, or may be a matter of lying in wait for prey to ambush. Some predators make use of camouflage, while others use aggressive mimicry, passing themselves off as a harmless creature. For example, the sabre-toothed blenny (Aspidontus taeniatus) closely resembles the cleaner wrasse (Labroides dimidiatus), both in its colouration and its behaviour. Large fish permit the cleaner wrasse to approach and remove parasites from their body surface and the inside of the mouth. The relationship is symbiotic, because the wrasse benefits by obtaining food and the host fish benefits by having parasites removed. Sometimes, the blenny is mistaken for the cleaner wrasse, in which case the mimic approaches the host fish, bites a piece from a fin, and escapes.