Apex predator

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Source: Wikipedia, the free encyclopedia.
For other uses, see Apex predator (disambiguation).

The lion is the world's second-largest big cat and serves as an apex land predator in Africa.[1][2]
The saltwater crocodile is the largest living reptile and the dominant predator throughout its range.[3][4]
The great white shark (bottom) is a known marine apex predator; however, the orca (killer whale, top) is known to be one as well. Despite coexisting the majority of the time, confrontations may occur in stressed environments when both species compete for limited resources.

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

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.

rewilding efforts, such as the proposed reintroduction of the Iberian lynx
.

Ecological roles

Effects on community

The great skua is an aerial apex predator, both preying on other seabirds and bullying them for their catches.[8]

Apex

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

Further information: Trophic cascade

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.

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]

Conservation

The wolf is both an apex predator and a keystone species, affecting its prey's behaviour and the wider ecosystem.

Because apex predators have powerful effects on other predators, herbivores, and plants, they can be important in nature conservation.[21] Humans have hunted many apex predators close to extinction, but in some parts of the world, these predators are now returning.[22] They are increasingly threatened by climate change. For example, the polar bear requires extensive areas of sea ice to hunt its prey, typically seals, but climate change is shrinking the sea ice of the Arctic, forcing polar bears to fast on land for increasingly long periods.[23]

Dramatic changes in the

gray wolf, both an apex predator and a keystone species (one with a large effect on its ecosystem), was reintroduced to Yellowstone National Park in 1995 as a conservation measure. Elk, the wolves' primary prey, became less abundant and changed their behavior, freeing riparian zones from constant grazing and allowing willows, aspens, and cottonwoods to flourish, creating habitats for beaver, moose, and scores of other species.[24] In addition to their effect on prey species, the wolves' presence also affected one of the park's vulnerable species, the grizzly bear: emerging from hibernation, having fasted for months, the bears chose to scavenge wolf kills,[25] especially during the autumn as they prepared to hibernate once again.[26] The grizzly bear gives birth during hibernation, so the increased food supply is expected to produce an increase in the number of cubs observed.[27] Dozens of other species, including eagles, ravens, magpies, coyotes, and black bears have also been documented as scavenging from wolf kills within the park.[28]

Human trophic level

Further information: Trophic level
Humans sometimes live by hunting other animals for food and materials such as fur, sinew, and bone, as in this walrus hunt in the Arctic, but humans' status as apex predators is debated.

Ecologists have debated whether humans are apex predators. For instance, Sylvain Bonhommeau and colleagues argued in 2013 that across the global food web, a fractional human trophic level (HTL) can be calculated as the mean trophic level of every species in the human diet, weighted by the proportion that that species forms in the diet. This analysis gives an average HTL of 2.21, varying between 2.04 (for Burundi, with a 96.7% plant-based diet) and 2.57 (for Iceland, with 50% meat and fish, 50% plants). These values are comparable to those of non-apex predators such as the anchovy or pig.[29]

However, Peter D. Roopnarine criticized Bonhommeau's approach in 2014, arguing that humans are apex predators and that the HTL was based on terrestrial farming where indeed humans have a low trophic level, mainly eating producers (crop plants at level 1) or primary consumers (herbivores at level 2), which as expected places humans at a level slightly above 2. Roopnarine instead calculated the position of humans in two marine ecosystems, a Caribbean coral reef and the

Benguela system near South Africa. In these systems, humans mainly eat predatory fish and have a fractional trophic level of 4.65 and 4.5, respectively, which in Roopnarine's view makes those humans apex predators.[b][30]

In 2021, Miki Ben-Dor and colleagues compared human biology to that of animals at various trophic levels. Using metrics as diverse as tool use and acidity of the stomach, they concluded that humans evolved as apex predators, diversifying their diets in response to the disappearance of most of the megafauna that had once been their primary source of food.[31]

Evolutionary history

Anomalocaris was an apex predator in the Cambrian seas.[32]
Further information: Predation § Evolutionary history

Apex predators are thought to have existed since at least the Cambrian period, around 500 million years ago. Extinct species cannot be directly determined to be apex predators as their behavior cannot be observed, and clues to ecological relationships, such as bite marks on bones or shells, do not form a complete picture. However, indirect evidence such as the absence of any discernible predator in an environment is suggestive. Anomalocaris was an aquatic apex predator, in the Cambrian. Its mouthparts are clearly predatory, and there were no larger animals in the seas at that time.[32]

Carnivorous

theropod dinosaurs including Allosaurus[33] and Tyrannosaurus[34]
are theorized to have been apex predators, based on their size, morphology, and dietary needs.

A

Cheliderpeton latirostre), one of which had consumed a fish, Acanthodes bronni, showing that the shark had lived at a trophic level of at least 4.[c][35]

Among more recent fossils, the saber-tooth cats, like Smilodon, are considered to have been apex predators in the Cenozoic.[36]

Interactions with humans

Dogs have been used in hunting for many centuries, as in this 14th century French depiction of a boar hunt.

Hunting

Further information: Hunting

Humans hunted with apex predators in the form of wolves, and in turn with

flush out, or retrieve prey.[39] The Portuguese Water Dog was used to drive fish into nets.[40] Several breeds of dog have been used to chase large prey such as deer and wolves.[41]

Eagles and falcons, which are apex predators, are used in falconry, hunting birds or mammals.[42] Tethered cormorants, also top predators,[43] have been used to catch fish.[44]

Ecotourism

Further information: Ecotourism
Tiger sharks are popular ecotourism subjects, but their ecosystems may be affected by the food provided to attract them.

big cats and crocodiles.[46]

Rewilding

Further information:
Rewilding (conservation biology)
The reintroduction of predators like the lynx is attractive to conservationists, but alarming to farmers.

In some densely populated areas like the

rewilding movement.[48] The reintroduction of large predators is controversial, in part because of concern among farmers for their livestock.[48] Conservationists such as Paul Lister propose instead to allow wolves and bears to hunt their prey in a "managed environment" on large fenced reserves; however, this undermines the objective of rewilding.[48]

Notes

  1. Zoologists generally exclude parasites from trophic levels as they are (often much) smaller than their hosts, and individual species with multiple hosts at different life-cycle stages would occupy multiple levels. Otherwise they would often be at the top level, above apex predators.[5]
  2. ^ However, humans had a network trophic level (NTL) of 4.27 in the coral reef system, compared to an NTL of 4.8 for the blacktip shark in the same system. Therefore, humans were not the topmost apex predator there.[30]
  3. ^ Its trophic level would be exactly 4 if the fish's prey were pure herbivores, higher if the prey were themselves carnivorous.

References

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  6. ^ "predator". Online Etymological Dictionary. Archived from the original on 2009-07-01. Retrieved 2010-01-25.
  7. ^ "apex predator". PBS. Archived from the original on 2009-07-22. Retrieved 2010-01-25.
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  24. ^ Lister, Brad & McDaniel, Carl. "The wolves of Yellowstone" Archived 2011-07-20 at the Wayback Machine (2006-04-17), p. 2. Retrieved 2010-01-25.
  25. ^ Levy, Sharon (November 2002). "Top Dogs". Archived from the original on 2009-06-06. Retrieved 2010-01-25.
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  27. ^ Robbins, Jim (May–June 1998). "Weaving a new web: wolves change an ecosystem". Smithsonian Zoogoer. 27 (3). Smithsonian Institution. Archived from the original on 10 February 2010. Retrieved 2010-01-25.
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  47. ^ Jones, Lucy. "The rewilding plan that would return Britain to nature". BBC. Retrieved 6 June 2018. wolves, bears and lynx roamed the land. ... Humans chopped down the trees to make space for farms, and hunted the large animals to extinction, leaving plant-eaters to decimate the country's flora. Britain is now one of the few countries in the world that doesn't have top predators.
  48. ^ a b c Lister, Paul (28 April 2015). "Bring on a few more apex predators". The Daily Telegraph. Archived from the original on 2022-01-11. Retrieved 14 March 2018.
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