Predation
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Predator eyes - an American alligator |
A
predator is an
animal or other
organism that hunts and kills other organisms, called
prey, for
food in an act called
predation.
Predators are either
carnivores or
omnivores. The difference between a predator and a
parasite is that for a predator
killing the prey is necessary for consuming it, but for parasites it is not even desirable because a parasite lives on or in its
host.
Herbivores also consume other species, but generally only in part, leaving the organism alive. However, where the prey consists of single-celled
algae, the activities of the herbivorous grazer is generally of the same nature as that of a carnivore. As often in
ecology there is seldom consensus on the distinctions; some ecologists prefer functional definitions like the one outlined above, others rather look at the
ecological dynamics the relationships between the species create. The
Volterra-Lotka equations describe a simple
mathematical model of the interaction between predators and their
prey.
There may be hierarchies of predators; for example, though small
birds prey on
insects, they may in turn be prey for
snakes, which may in turn be prey for
hawks. A predator at the top of its
food chain (that is, one that is preyed upon by no organism) is called an
apex predator; examples include the
Great White Shark,
tiger and
crocodile and even omnivorous
Humans. Such predators may have a profound influence on the balance of organisms in a particular
ecosystem; introduction or removal of this predator, or changes in its population, can have drastic cascading effects on the equilibrium of many other populations in the ecosystem.
Many predators specialize in hunting only one species of prey. Others are more opportunistic and will kill and eat almost anything. The specialists are usually particularly well suited to capturing their preferred prey. The prey in turn, are often equally suited to escape that predator. This is called an evolutionary
arms race and tends to keep the populations of both species in equilibrium.
There is a full spectrum of specialization. Some predators specialize in certain classes of prey, not just single species. Almost all will switch to other prey (with varying degrees of success) when the preferred target is extremely scarce.
Contrary to conventional belief, predation is not typically an indiscriminate urge to kill other living beings. When hunger is not an issue for the animal, most predators will typically not seek to attack prey since the basic need is absent and it is a waste of energy to do so. For instance, a large predator fish like a
shark that is well fed in an
aquarium will typically ignore the smaller fish swimming around it (while the prey fish take advantage of the fact that the
apex predator is apparently uninterested).
It has been observed that well-fed predator animals in a lax captivity (for instance,
pet or
farm animals) will usually differentiate between putative prey animals who are familiar co-inhabitants in the same human area from wild ones outside the area. This interaction can range from peaceful coexistence to close companionship; motivation to ignore the predatory instinct may result from mutual advantage or fear of reprisal from human masters who have made clear that harming co-inhabitants will not be tolerated. Pet cats and pet mice, for example, may live together in the same human residence without incident as companions. Pet cats and pet dogs under human mastership often depend on each other for warmth, companionship, and even protection, particularly in rural areas.
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Biological pest control*
Scavenger
