Apex predator

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For the Napalm Death album, see Apex Predator – Easy Meat.

An apex predator, also known as an alpha predator, super predator, top predator or top-level predator, is a predator residing at the top of a food chain on which no other creatures predate.[n 1][1][2] 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.[3] 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: humans,[4] for example, are both apex predators and omnivores.[5]

Ecological role[edit]

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.[6]

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.[7] 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.[8][9]

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.[10] 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,[11][12]:56 especially during the autumn as they prepared to hibernate once again.[12]: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.[13] Dozens of other species, including eagles, ravens, magpies, coyotes and black bears have also been documented as scavenging from wolf kills within the park.[14]

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.[15]

Gallery[edit]

Notes[edit]

  1. ^ Zoologists generally define predation as the non-parasitical or non-bacterial killing and consumption of organisms.[citation needed]

References[edit]

  1. ^ "predator". Online Etymological Dictionary. Retrieved 2010-01-25. 
  2. ^ "apex predator". PBS. Retrieved 2010-01-25. 
  3. ^ 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. 
  4. ^ Archer, Michael: "Slime Monsters Will Be Human Too" in Nature Australia vol. 22 (1989).
  5. ^ Haenel H (1989). "Phylogenesis and nutrition". Nahrung 33 (9): 867–87. PMID 2697806. 
  6. ^ Lepak, Jesse M.; Kraft, Clifford E., Weidel, Brian C. (March 2006). "Rapid food web recovery in response to removal of an introduced apex predator" (PDF). Canadian Journal of Fisheries and Aquatic Sciences 63 (3): 569–575. ISSN: 0706-652X. Retrieved 2010-01-25.
  7. ^ 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. 
  8. ^ 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. 
  9. ^ 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. 
  10. ^ Bystroff, Chris, "The wolves of Yellowstone" (2006-04-17), p. 2. Retrieved 2010-01-25.
  11. ^ Levy, Sharon (November 2002). "Top Dogs". Retrieved 2010-01-25. 
  12. ^ a b Wilmers, Christopher C. (2004). "The gray wolf – scavenger complex in Yellowstone National Park" (PDF). Retrieved 2010-01-25. 
  13. ^ 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. 
  14. ^ Wilmers, Christopher C.; Getz, Wayne M. (April 2005). "Gray wolves as climate change buffers in Yellowstone". PLoS Biology 3 (4): e92. doi10.1371/journal.pbio.0030092. Retrieved 2010-01-25.
  15. ^ 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.
  16. ^ "Saltwater Crocodile." National Geographic. Retrieved 2010-01-25.
  17. ^ Whiting, Frances. "Terri fights to halt croc eggs harvest." Australia Zoo. 2007-06-11. Retrieved 2010-01-25.
  18. ^ "Orcinus orca – Orca (Killer Whale)". Marinebio.org. Retrieved 2012-03-04. 
  19. ^ "Evolution and General Intelligence: Three hypotheses on the evolution of general intelligence.". Scientific American. 1998. Retrieved 30 October 2013.