An apex predator, also known as an alpha predator or apical predator, is a predator residing at the top of a food chain upon which no other creatures prey. Apex predators are usually defined in terms of trophic dynamics, meaning that apex-predator species occupy the highest trophic level or levels and play 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.
Food chains are often far shorter on land, with their apices usually limited to the third trophic level – for example, giant constrictor snakes, crocodilians, hyenas, wolves or big cats preying mostly upon large herbivores. Apex predators do not need to be hypercarnivores.
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 was removed, lake trout, the suppressed native apex predator, diversified its prey selection and increased its trophic level.
Effects on wider ecosystem characteristics such as plant ecology have been debated, but there is evidence of a significant impact by apex predators. When introduced to subarctic islands, for example, Arctic foxes' predation of seabirds has been shown to turn grassland into tundra. Such wide-ranging effects on lower levels of an ecosystem are termed trophic cascades. The removal of top-level predators, often – and, especially, recently – through human agency, can radically cause or disrupt trophic cascades.
A now commonly cited example of the effect of apex predators on an ecosystem is the dramatic changes in the Greater Yellowstone Ecosystem recorded after the gray wolf was reintroduced to Yellowstone National Park in 1995. 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. 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,:56 especially during the autumn as they prepared to hibernate once again.:90 The grizzly bear gives birth during hibernation, so the increased food supply is expected to produce an increase in the numbers of cubs observed. Dozens of other species, including eagles, ravens, magpies, coyotes and black bears have also been documented as scavenging from wolf kills within the park.
Keystone species, a concept first described by zoologist Robert Paine to explain the relationship between the starfish species Pisaster ochraceus and mussel species Mytilus californianus, are apex predators within functional groups.
The question of whether or not homo sapiens qualifies as an apex predator is a complex one that has been subject to various analyses for years. The highly varied environments that human beings have lived in (and continue to live in) coupled with the similarly highly varied behaviors of human cultures towards animals make generalizations particularly difficult; though as omnivores that far and away consume more plant matter than meat, humans have the organized ability to drive other species into extinction as well as threatened status vastly unlike any other animal. The topic has been explored in publications such as the Proceedings of the National Academy of Sciences and Scientific American, with disputed results.
Humans range from complete vegetarians to nearly-complete carnivores, so the status of humans even as predators is often suspect even if armed humans are extremely dangerous to any animal. When hunting with firearms, dogs, falcons, or such tools as spears, snares, clubs, or fishing gear, humans are at least local superpredators along with their dogs.
Wolves operate in packs in which each wolf has a specialized role in hunts that would otherwise fail, often against prey much larger than the individual wolves. All wolf subspecies, including dogs and dingos, and the closely related coyote, are successful predators and may sometimes prey on livestock and vermin—and are competent defenders.
The tiger is one of the largest non-aquatic mammalian predators in the world. Pictured is the Bengal tiger, the subspecies of tiger most infamous for man-eating. All members of the cat family, including even the domestic cat with obvious similarities of build and behavior to tigers and leopards, are consummate predators irrespective of size.
The reticulated python, one of the largest snakes, has only its long, powerful body as a weapon. But that body is enough to kill by suffocation of its victims, and any animal that can avoid it stays out of its reach.
The whale shark, the world's largest shark and fish, has a reputation as a "gentle giant" as a filter feeder. Despite having no prey larger than small fish, it has no natural predators and is an apex predator.
With this lethal mouth and a powerful swing of its tail, the American alligator has only armed humans and larger alligators to fear in the swamps of subtropical and tropical North America in which this predator lives.
Convergent evolution has given the Tasmanian devil a superficial similarity to such small, formidable apex predators among the Carnivora as badgers and terrier dogs—but they are very different mammals of the marsupial order. They are similarly deadly to small animals as true Carnivorans of like size.
Driver ants, also known as siafu, are intrepid predators despite their blindness and the smallness of individual ants. This is due to the size of their swarms. Excruciating pain from their bites keeps larger animals from attacking them.
Tyrannosaurus rex was one of the largest carnivorous dinosaurs, possibly growing to lengths of over 12.8 meters (42 feet) and weighing 6 to 10 tons, it was one of the most supreme predators of its time. It is estimated to have been capable of exerting the largest bite force among all terrestrial animals.
- "Saltwater Crocodile." National Geographic. Retrieved 2010-01-25.
- Whiting, Frances. "Terri fights to halt croc eggs harvest." Australia Zoo. 2007-06-11. Retrieved 2010-01-25.
- "Orcinus orca – Orca (Killer Whale)". Marinebio.org. Retrieved 2012-03-04.
- "predator". Online Etymological Dictionary. Retrieved 2010-01-25.
- "apex predator". PBS. Retrieved 2010-01-25.
- Essington, Timothy E.; Beaudreau, Anne H.; Wiedenmann, John (December 2005). "Fishing through marine food webs" (PDF). Proceedings of the National Academy of Sciences. 103 (9): 3171–3175. doi:10.1073/pnas.0510964103. PMC 1413903. PMID 16481614. Retrieved 2010-01-25.
- Lepak, Jesse M.; Kraft, Clifford E., Weidel, Brian C. (March 2006). "Rapid food web recovery in response to removal of an introduced apex predator" Archived September 11, 2008, at the Wayback Machine. (PDF). Canadian Journal of Fisheries and Aquatic Sciences 63 (3): 569–575. ISSN 0706-652X. Retrieved 2010-01-25.
- Croll, D. A.; Maron, J. L.; et al. (March 2005). "Introduced predators transform subarctic islands from grassland to tundra". Science. 307 (5717): 1959–1961. doi:10.1126/science.1108485. PMID 15790855. Retrieved 2010-01-25.
- Egan, Logan Zane; Téllez, Jesús Javier (June 2005). "Effects of preferential primary consumer fishing on lower trophic level herbivores in the Line Islands" (PDF). Stanford at Sea. Stanford University. Retrieved 2010-01-25.
- Pace, M. L.; Cole, J. J.; et al. (December 1999). "Trophic cascades revealed in diverse ecosystems". Trends in Ecology and Evolution. 14 (12): 483–488. doi:10.1016/S0169-5347(99)01723-1. PMID 10542455.
- Bystroff, Chris, "The wolves of Yellowstone" (2006-04-17), p. 2. Retrieved 2010-01-25.
- Levy, Sharon (November 2002). "Top Dogs". Retrieved 2010-01-25.
- Wilmers, Christopher C. (2004). "The gray wolf – scavenger complex in Yellowstone National Park" (PDF). Retrieved 2010-01-25.
- Robbins, Jim (May–June 1998). "Weaving a new web: wolves change an ecosystem". Smithsonian Zoogoer. Smithsonian Institution. 27 (3). Archived from the original on 10 February 2010. Retrieved 2010-01-25.
- Wilmers, Christopher C.; Getz, Wayne M. (April 2005). "Gray wolves as climate change buffers in Yellowstone". PLoS Biology 3 (4): e92. doi: 10.1371/journal.pbio.0030092. Retrieved 2010-01-25.
- Davic, Robert D (2003). "Linking keystone species and functional groups: a new operational definition of the keystone species concept". Conservation Ecology 7 (1): r11. Retrieved 2010-01-25.
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