Apex predator
Encyclopedia
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...
. Zoologists define predation as the killing and consumption of another organism (which generally excludes parasites
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
and most bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
). In this context, "apex predator" is usually defined in terms of trophic dynamics. Apex predator species occupy the highest trophic level
Trophic level
The trophic level of an organism is the position it occupies in a food chain. The word trophic derives from the Greek τροφή referring to food or feeding. A food chain represents a succession of organisms that eat another organism and are, in turn, eaten themselves. The number of steps an organism...
(s) and have a crucial role in maintaining the health of their ecosystems. One study of marine food webs defined apex predators as greater than trophic level four. The apex predator concept is commonly applied in wildlife management, conservation, and ecotourism
Ecotourism
Ecotourism is a form of tourism visiting fragile, pristine, and usually protected areas, intended as a low impact and often small scale alternative to standard commercial tourism...
.
Food chains are often far shorter on land, with the top of the food chain limited to the third trophic level, as where such predators as the big cat
Big cat
The term big cat – which is not a biological classification – is used informally to distinguish the larger felid species from smaller ones. One definition of "big cat" includes the four members of the genus Panthera: the tiger, lion, jaguar, and leopard. Members of this genus are the only cats able...
s, crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
ns, hyena
Hyena
Hyenas or Hyaenas are the animals of the family Hyaenidae of suborder feliforms of the Carnivora. It is the fourth smallest biological family in the Carnivora , and one of the smallest in the mammalia...
s, wolves
Gray Wolf
The gray wolf , also known as the wolf, is the largest extant wild member of the Canidae family...
, or giant constrictor snakes prey upon large herbivores. Apex predators need not be hypercarnivore
Hypercarnivore
A hypercarnivore is an animal which has a diet that is more than 70% meat, with the balance consisting of non-animal foods such as fungi, fruits or other plant material. Some examples include the big cats, dolphins, eagles, snakes, marlin, most sharks, and such invertebrates as octopuses and sea...
s. For example, grizzly bear
Grizzly Bear
The grizzly bear , also known as the silvertip bear, the grizzly, or the North American brown bear, is a subspecies of brown bear that generally lives in the uplands of western North America...
s and human
Human
Humans are the only living species in the Homo genus...
s are each apex predators and are omnivores. A dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
, more carnivorous than either humans or most bears, is usually more of a scavenger
Scavenger
Scavenging is both a carnivorous and herbivorous feeding behavior in which individual scavengers search out dead animal and dead plant biomass on which to feed. The eating of carrion from the same species is referred to as cannibalism. Scavengers play an important role in the ecosystem by...
than a predator, but as an occasional killer of livestock or wildlife and a participant in some human hunts it qualifies as a superpredator in much of its extensive range; this is especially true of giant molosser
Molosser
Molosser is a category of large, solidly-built dog that includes several breeds, probably all descended from the same root stock. The name derives from Molossia, a subregion of ancient Epirus, ancient Greece, where the large shepherd dog was known as the Molossus.The proper noun "Mastiff", however,...
breeds that have for their size the strength, power, agility, speed, cunning, intelligence, and aggression characteristic of wolves, bears, big cats, and hyenas but unlike those other predators do not ordinarily prey on humans
Man-eater
Man-eater is a colloquial term for an animal that preys upon humans. This does not include scavenging. Although human beings can be attacked by many kinds of animals, man-eaters are those that have incorporated human flesh into their usual diet...
. In this sense, an apex predator can be defined as being too difficult to kill for them to be a regular source of food for other predators. Some animals may be superpredators in some environments but not others, such as domestic dogs and cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s, both of which can ravage ecosystems (see Stephens Island Wren
Stephens Island Wren
The Stephens Island Wren or Lyall's Wren was a nocturnal, flightless, insectivorous passerine.-Habitat:...
).
Ecological role
- See also Mesopredator release hypothesisMesopredator release hypothesisThe mesopredator release hypothesis is a relatively new hypothesis from 1988 which describes the phenomenon of trophic cascade in certain terrestrial communities. It states that as top predators decline in an ecosystem, an increase in the populations of mesopredators occurs...
Apex predators affect prey species' population dynamics. Where two competing species are in an ecologically unstable relationship, apex predators tend to create stability if they prey upon both. Inter-predator relationships are also affected by apex status. Non-native fish, for example, have been known to devastate formerly dominant predators. One lake manipulation study found that when the non-native smallmouth bass
Smallmouth bass
The smallmouth bass is a species of freshwater fish in the sunfish family of the order Perciformes. It is the type species of its genus...
was removed, lake trout
Lake trout
Lake trout is a freshwater char living mainly in lakes in northern North America. Other names for it include mackinaw, lake char , touladi, togue, and grey trout. In Lake Superior, they can also be variously known as siscowet, paperbellies and leans...
, the suppressed native apex predator, diversified its prey selection and increased its trophic level
Trophic level
The trophic level of an organism is the position it occupies in a food chain. The word trophic derives from the Greek τροφή referring to food or feeding. A food chain represents a succession of organisms that eat another organism and are, in turn, eaten themselves. The number of steps an organism...
.
Effects on wider ecosystem characteristics, such as plant ecology
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
, have been debated, but there is evidence of a significant impact by apex predators: introduced arctic fox
Arctic fox
The arctic fox , also known as the white fox, polar fox or snow fox, is a small fox native to Arctic regions of the Northern Hemisphere and is common throughout the Arctic tundra biome. The Greek word alopex, means a fox and Vulpes is the Latin version...
es, for example, have been shown to turn subarctic islands from grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...
into tundra
Tundra
In physical geography, tundra is a biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра from the Kildin Sami word tūndâr "uplands," "treeless mountain tract." There are three types of tundra: Arctic tundra, alpine...
through predation on seabird
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
s. Such wide-ranging effects on lower levels of an ecosystem are termed trophic cascade
Trophic cascade
Trophic cascades occur when predators in a food web suppress the abundance of their prey, thereby releasing the next lower trophic level from predation...
s. The removal of top-level predators, often, recently, through human agency, can radically cause (or disrupt) trophic cascades. A commonly cited example of apex predators affecting an ecosystem is Yellowstone National Park
Yellowstone National Park
Yellowstone National Park, established by the U.S. Congress and signed into law by President Ulysses S. Grant on March 1, 1872, is a national park located primarily in the U.S. state of Wyoming, although it also extends into Montana and Idaho...
. After the reintroduction of the gray wolf
Gray Wolf
The gray wolf , also known as the wolf, is the largest extant wild member of the Canidae family...
in 1995, researchers noticed drastic changes occurring in the Greater Yellowstone Ecosystem
Greater Yellowstone Ecosystem
The Greater Yellowstone Ecosystem is one of the last remaining large, nearly intact ecosystems in the northern temperate zone of the Earth and is partly located in Yellowstone National Park. Conflict over management has been controversial, and the area is a flagship site among conservation groups...
. Elk
Elk
The Elk is the large deer, also called Cervus canadensis or wapiti, of North America and eastern Asia.Elk may also refer to:Other antlered mammals:...
, the primary prey of the gray wolf, became less abundant and changed their behavior, freeing riparian zone
Riparian zone
A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the fifteen terrestrial biomes of the earth. Plant habitats and communities along the river margins and banks are called riparian vegetation, characterized by...
s from constant grazing. The respite allowed willows, aspens, and cottonwoods to grow, creating habitat for beaver
Beaver
The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...
, moose
Moose
The moose or Eurasian elk is the largest extant species in the deer family. Moose are distinguished by the palmate antlers of the males; other members of the family have antlers with a dendritic configuration...
, and scores of other species. In addition to the effects on prey species, the gray wolf's presence also affected the park's grizzly bear
Grizzly Bear
The grizzly bear , also known as the silvertip bear, the grizzly, or the North American brown bear, is a subspecies of brown bear that generally lives in the uplands of western North America...
, a vulnerable species
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...
. The bears, emerging from hibernation, chose to scavenge off wolf kills after fasting for months. They can also eat wolf kills in autumn to prepare for hibernation. As grizzly bears give birth during hibernation, a greater food supply may improve the mother’s nutrition and increase the number of cubs. Dozens of other species, including eagles, ravens, magpies, coyotes, and black bears, have been documented scavenging from wolf kills. Keystone species
Keystone species
A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance. Such species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and...
are apex predators within functional groups, a concept first described by zoologist Robert Paine
Robert T. Paine (zoologist)
Robert T. Paine, PhD, is a zoologist and professor emeritus of the University of Washington,who coined the keystone species concept in order to explain the relationship between Pisaster ochraceus, a species of starfish, and Mytilus californianus, a species of mussel.In his classic 1966 paper, Dr...
to explain the relationship between Pisaster ochraceus, a species of starfish, and Mytilus californianus, a species of mussel
Mussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
.