In an ecosystem, predation is a biological interaction where a
predator (an organism that is hunting) feeds on its prey (the organism
that is attacked). Predators may or may not kill their prey prior
to feeding on it, but the act of predation often results in the death
of the prey and the eventual absorption of the prey's tissue through
Predation is often, though not always, carnivory, one of
several heterotrophic consumer-resource interactions. Different
feeding behaviors such as parasitism, parasitoidism, micropredation
and predation form a continuum rather than being entirely separate
Predation strategies can be classified by trophic level
or diet, by specialization, and by the predator's interaction with
Coevolutionary selective pressures imposed on each other by predator
and prey often result in an evolutionary arms race, resulting in
antipredator adaptations in the prey and adaptations that improve
hunting efficiency in the predator.
1 By function
1.1 True predation
2 Ecological interactions
2.2 Trophic level
2.3 As competition
2.5 Optimal foraging
2.6 Social predation
2.7 Size-selective predation
2.8 Antipredator adaptations
2.9 Predator camouflage and aggressive mimicry
2.10 Population dynamics
3 See also
5 Further reading
6 External links
Main article: Consumer-Resource Systems
Predators can be classified by their consumer-resource interactions
with their prey. Two factors are considered here: how close the
predator and prey (or host) are, and whether the prey is directly
killed by the predator, where true predation and parasitoidism involve
Humpback whales filtering thousands of krill from seawater, using
their baleen systems
A true predator is one that kills and eats another living thing.
Predators may hunt actively for prey in pursuit predation, or sit and
wait for prey to approach within striking distance in ambush
predation. Some predators kill large prey and dismember or chew
it prior to eating it, as do humans; others may eat their prey whole,
as do bottlenose dolphins swallowing fish, white storks
swallowing frogs, or baleen whales swallowing thousands of krill or
small fish at once. Some predators use venom to subdue their prey
before the predator ingests it, as in the box jellyfish, while the
venom of rattlesnakes and some spiders also helps to digest the
Seed and egg predation are true predation, as seeds and
eggs are potential organisms.
Main article: Grazing
Grazing animals generally do not kill their prey, but like predators,
they live by feeding on other organisms. While some herbivores like
zooplankton live on unicellular phytoplankton and therefore inevitably
kill what they eat, in a relationship sometimes called predation,
many others including cattle and sheep only eat a part of the plants
that they graze. Many species of plant are adapted to regrow after
grazing damage. For example, the growing meristems of grasses are not
at the tips as they are in most flowering plants, but at the base of
the leaves. Similarly, kelp is grazed in subtidal kelp forests,
but continuously regrows from a meristem at the base of the blade
where it joins the stipe. Animals may also be 'grazed' upon;
micropredators such as female mosquitoes land on hosts briefly to
feed on blood. Herbivore-plant interactions, as with predator-prey
interactions, have driven plants to evolve defences such as thorns and
chemicals to dissuade grazing.
Main article: Parasitism
Tapeworm Taenia solium, a parasite, has hooks and suckers on its head
to attach to its host.
Parasites, like predators, live by feeding on another organism. The
E. O. Wilson
E. O. Wilson has characterised parasites as "predators
that eat prey in units of less than one". Parasites often do not
kill their hosts, the exception being parasitoids which always do,
thus blurring the line between parasitism and predation. Equally,
small parasites such as mosquitoes exploit their hosts much as
micropredators such as moth caterpillars on an oak tree and grazers
do, though endoparasites in particular have a close association with
their host species; again there is essentially a continuum between
these feeding interactions.
Main article: Parasitoid
Parasitoids are organisms living in or on their host and feeding
directly upon it, eventually leading to its death. They are much like
parasites in their close associations with their hosts. Unlike typical
parasites, they always kill their hosts, but often not instantly.
Parasitoid wasps are solitary insects that live a free life as adults,
laying eggs on or in other insects such as lepidopteran caterpillars.
The wasp larvae feed on the growing host, eventually killing it.
Parasitoids make up as much as 10% of all insect species.
Platydemus manokwari is a flatworm predator of land snails.
Further information: Generalist and specialist species
Predators are often highly specialized, where for example the Eurasian
lynx only hunts small ungulates. Others such as leopards are more
opportunistic generalists. The specialists may be highly adapted
to capturing their preferred prey, whereas generalists may be better
able to switch to other prey when a preferred target is scarce. When
prey have a clumped (uneven) distribution, the optimal strategy for
the predator is to be more specialized as the prey are more
conspicuous and can be found more quickly.
A secondary consumer in action: a mantis (Tenodera aridifolia) eating
Trophic level and Trophic dynamics
Predators are often another organism's prey, and likewise prey are
often predators. Though blue jays prey on insects, they may in turn be
prey for cats and snakes, and snakes may be the prey of hawks. One way
of classifying predators is by trophic level. Carnivores that feed on
heterotrophs are secondary consumers; their predators are tertiary
consumers, and so forth. Because only a fraction of energy is passed
on to the next level, this hierarchy of predation must end somewhere,
and very seldom goes higher than five or six levels. For example, a
lion, an apex predator (at the top of its food chain) that preys upon
large herbivores such as wildebeest, which in turn eat grasses, is
only a secondary consumer. Other apex predators include the sperm
whale, Komodo dragon, tiger, and most eagles and owls. Many predators
eat from multiple levels of the food chain. A carnivore may eat both
secondary and tertiary consumers, and its prey may itself be difficult
to classify for similar reasons.
An alternative view offered by
Richard Dawkins is of predation as a
form of competition: the genes of both the predator and prey are
competing for the body (or 'survival machine') of the prey
organism. This is best understood in the context of the gene
centered view of evolution. Another manner in which predation and
competition are connected is throughout intraguild predation.
Intraguild predators are those that kill and eat other predators of
different species at the same trophic level, and thus that are
Riparian willow recovery at Blacktail Creek, Yellowstone National
Park, after reintroduction of wolves
Predators may increase the biodiversity of communities by preventing a
single species from becoming dominant. Such predators are known as
keystone species and 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 density, can have drastic
cascading effects on the equilibrium of many other populations in the
ecosystem. For example, grazers of a grassland may prevent a single
dominant species from taking over.
The elimination of wolves from
Yellowstone National Park
Yellowstone National Park had profound
impacts on the trophic pyramid. Without predation, herbivores began to
over-graze many woody browse species, affecting the area's plant
populations. In addition, wolves often kept animals from grazing in
riparian areas, which protected beavers from having their food sources
encroached upon. The removal of wolves had a direct effect on beaver
populations, as their habitat became territory for grazing.
Furthermore, predation keeps hydrological features such as creeks and
streams in normal working order. Increased browsing on willows and
conifers along Blacktail Creek due to a lack of predation caused
channel incision because the beavers helped slow the water down,
allowing soil to stay in place.
Optimal foraging theory
Optimal foraging theory and Consumer-resource systems
While successful predation results in a gain of energy, hunting
invariably involves energetic costs. When not hungry, predators stop
hunting, since the costs outweigh the benefits. For instance, a large
well-fed predatory fish like a shark in an aquarium ignores prey fish
Surplus killing represents a deviation from this behaviour.
The treatment of consumption in terms of cost-benefit analysis is
called optimal foraging theory, and has been successful in explaining
much animal behavior.
Wolves cooperating to hunt bison
In social predation, a group of predators cooperates to kill creatures
larger than those they could overpower singly. Social predators such
as ions, hyenas, and wolves collaborate to catch and kill large
herbivores. By hunting socially chimpanzees can catch colobus monkeys
that would readily escape an individual hunter, while a cooperating
group of Harris hawks can trap rabbits.
In size-selective predation, predators select prey of a certain size.
Large prey may prove troublesome for a predator, while small prey
might prove hard to find and in any case provide less of a reward.
This has led to a correlation between the size of predators and their
prey. Size may also act as a refuge for large prey. For example,
adult elephants are relatively safe from predation by lions, but
juveniles are vulnerable.
Lion and cub eating an African buffalo
A juvenile red-tailed hawk eating a California vole
Great blue heron
Great blue heron with a speared fish
Jungle-runner lizard eating a rat
Indian python swallowing a chital
Main article: Antipredator adaptation
Springbok stotting to advertise its ability to escape
Many antipredator adaptations have evolved in prey populations due to
the selective pressures of predation over long periods of time. Some
species mob predators cooperatively. Others such as Thomson's gazelle
stot to signal to predators such as cheetahs that they will have an
unprofitable chase. Many prey animals are aposematically colored
or patterned as a warning to predators that they are distasteful or
able to defend themselves. Such distastefulness or toxicity is
brought about by chemical defenses, found in a wide range of prey,
especially insects, but the skunk is a dramatic mammalian example.
Chemical defences can include toxins, such as bitter compounds in
leaves, often absorbed by leaf-eating insects such as caterpillars and
used to dissuade potential predators.
Camouflage of the dead leaf mantis makes it less visible to both its
predators and its prey.
Camouflage makes use of coloration, shape, and pattern to misdirect
the visual sensory mechanisms of predators, enabling prey to remain
unrecognized. Among the many mechanisms of camouflage are blending
in with ones background, countershading, and disruptive coloration.
The resemblance can be to the biotic or non-living environment, such
as a mantis resembling dead leaves, or to other organisms. In mimicry,
an organism has a similar appearance to another species, as in the
drone fly, which resembles a bee, yet has no sting. Many butterflies
and moths have wing markings that resemble eyes. When a predator
disturbs the insect, it reveals its hind wings, startling the predator
and giving it time to escape.
Predator camouflage and aggressive mimicry
A camouflaged predator: snow leopard in
Ladakh (Photo by Tashi
Striated frogfish uses camouflage and aggressive mimicry in the form
of a fishing rod-like lure on its head to attract prey.
Further information: Aggressive mimicry
Predators use stealth, camouflage and aggressive mimicry to improve
their hunting efficiency. Members of the cat family such as the snow
leopard (treeless highlands), tiger (grassy plains, reed swamps),
ocelot (forest), fishing cat (waterside thickets), and lion (open
plains) have coloration and patterns suiting their habitats.
Female Photuris fireflies, for example, copy the light signals of
other species, thereby attracting male fireflies, which they capture
and eat. Flower mantises are ambush predators; camouflaged as
flowers, such as orchids, they attract prey and seize it when it is
close enough. Frogfishes are extremely well camouflaged, and
actively lure their prey to approach using an esca, a bait on the end
of a rod-like appendage on the head, which they wave gently to mimic a
small animal, gulping the prey in an extremely rapid movement when it
is within range.
Predators tend to lower the survival and fecundity of their prey, and
depend on prey for their survival, so predator populations are
affected by changes in prey populations and vice versa. The
population dynamics of predator–prey interactions can be modelled
using the Lotka–Volterra equations. These provide a mathematical
model for the cycling of predator and prey populations. Predators tend
to select young, weak, and ill individuals.
Predation appears to have become a major selection pressure shortly
Cambrian period—around 550 million years ago—as
evidenced by the almost simultaneous development of calcification in
animals and algae, and predation-avoiding burrowing. However,
predators had been grazing on micro-organisms since at least
1,000 million years ago.
Humans and dogs as a predatory team
Humans are to some extent predatory, fishing, hunting and trapping
animals using weapons and tools. They also use other predatory
species, such as dogs, cormorants, and falcons to catch prey for
food or for sport.
In biological pest control, predators from a pest's natural range are
introduced to control populations, at the risk of causing unforeseen
problems. Natural predators are an environmentally friendly and
sustainable way of reducing damage to crops, and are an alternative to
the use of chemical agents such as pesticides.
Bird of prey
Built for the Kill, a nature series on predators
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