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An apex predator, also known as a top predator or superpredator, is a predator[a] at the top of a food chain, without natural predators of its own.[6][7]
Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the highest trophic levels. Food chains are often far shorter on land, usually limited to being secondary consumers – for example, wolves prey mostly upon large herbivores (primary consumers), which eat plants (primary producers). The apex predator concept is applied in wildlife management, conservation, and ecotourism.
Apex predators have a long evolutionary history, dating at least to the Cambrian period when animals such as Anomalocaris and Timorebestia dominated the seas.
Humans have for many centuries interacted with other apex predators including the wolf, birds of prey, and cormorants to hunt game animals, birds, and fish respectively. More recently, humans have started interacting with apex predators in new ways. These include interactions via ecotourism, such as with the tiger shark, and through rewilding efforts, such as the proposed reintroduction of the Iberian lynx.
Ecological roles
[edit]Effects on community
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Apex predators affect prey species' population dynamics and populations of other predators, both in aquatic and terrestrial ecosystems. Non-native predatory fish, for instance, have sometimes devastated formerly dominant predators. A lake manipulation study found that when the non-native smallmouth bass was removed, lake trout, the suppressed native apex predator, diversified its prey selection and increased its trophic level.[9] As a terrestrial example, the badger, an apex predator, preys upon and also competes with the hedgehog, a mesopredator, for food such as insects, small mammals, reptiles, amphibians, and the eggs of ground-nesting birds. Removal of badgers (in a trial investigating bovine tuberculosis) caused hedgehog densities to more than double.[10] Predators that exert top-down control on organisms in their community are often considered keystone species.[11]
Effects on ecosystem
[edit]Apex predators can have profound effects on ecosystems, as the consequences of both controlling prey density and restricting smaller predators, and may be capable of self-regulation.[12] They are central to the functioning of ecosystems, the regulation of disease, and the maintenance of biodiversity.[13] When introduced to subarctic islands, for example, Arctic foxes' predation of seabirds has been shown to turn grassland into the tundra.[14] Such wide-ranging effects on lower levels of an ecosystem are termed trophic cascades. The removal of top-level predators, often through human agency, can cause or disrupt trophic cascades.[15][16][17] For example, a reduction in the population of sperm whales, apex predators with a fractional trophic level of 4.7, by hunting has caused an increase in the population of the large squid, with trophic level over 4 (carnivores that eat other carnivores).[18] This effect, called mesopredator release,[19] occurs in terrestrial and marine ecosystems; for instance, in North America, the ranges of all apex carnivores have contracted whereas those of 60% of mesopredators have grown in the past two centuries.[20]