- Apex predator
Apex predators (also alpha predators, superpredators, or top-level predators) are
predatorsthat, as adults, are not normally preyed upon in the wild in significant parts of their range. Apex predator species are often at the end of long food chains, where they have a crucial role in maintaining the health of ecosystems.
The term has been defined in terms of
trophic levels. Trophic levels are "hierarchical strata of a food web characterized by organisms which are the same number of steps removed from the primary producers." [cite web |url=http://www.merriam-webster.com/dictionary/trophic+level
title=Trophic level |accessdate=2008-06-02 |publisher=Merriam-Webster Dictionary|date= ] Primary, secondary, tertiary, and higher level consumers occupy successive trophic levels. One study of marine food webs defined apex predators as greater than trophic level four. [cite journal |last=Essington |first=Timothy E. |coauthors= Beaudreau, Anne H.; Wiedenmann, John |year=2005 |month=December |title=Fishing through marine food webs |journal= Proceedings of the National Academy of Sciences|volume=103 |issue=9 |pages=3171–3175 |url=http://www.pnas.org/cgi/reprint/0510964103v1.pdf |accessdate= 2007-11-24 |format=PDF]
Mesopredator release hypothesis."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. [cite journal |last= Tasku|first= Cheon |coauthors=Ohta, Shigemi |year=2004 |month=August |title=Suppression of ecological competition by an apex predator |journal=Physical Review |volume=70 |issue=2 |pages= |doi=10.1103/PhysRevE.70.021913 |url=http://adsabs.harvard.edu/abs/2004PhRvE..70b1913C |accessdate= 2007-11-24 ] Inter-predator relationships are also affected by apex status. Non-native fishes, for example, have been known to devastate formerly dominant predators. One lake manipulation study found that when the non-native smallmouth basswas removed, lake trout, the suppresed native apex predator, diversified its prey selection and increased its trophic level.Lepak, Jesse M., Kraft, Clifford E., and Weidel, Brian C. (March 2006). " [http://www.dnr.cornell.edu/cek7/Publications/Lepak_et_al_2006.pdf 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 on 2008- 06-03.]
Effects on wider ecosystem characteristics, such as plant
ecology, have been debated, but there is evidence of a significant impact by apex predators: introduced arctic foxes, for example, have been shown to turn subarctic islands from grassland into tundra through predation on seabirds. [cite journal |last=Croll |first=D. A. |coauthors=Maron, J. L.; et al. |year= 2005|month=March |title=Introduced Predators Transform Subarctic Islands from Grassland to Tundra |journal=Science |volume=307 |issue=5717 |pages=1959 - 1961 | url=http://www.sciencemag.org/cgi/content/abstract/307/5717/1959 |accessdate= 2007-11-24 |doi=10.1126/science.1108485 ] 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 radically cause (or disrupt) trophic cascades. [cite web |last= Egan|first=Logan Zane |coauthors=Téllez, Jesús Javier |year=2005 |month=June |title=Effects of preferential primary consumer fishing on lower trophic level herbivores in the Line Islands |work=Stanford at Sea |publisher= Stanford University|url=http://stanford.sea.edu/research/EganTellez_Research_Project.pdf |accessdate= 2007-11-24 |format=PDF ] [cite journal |last=Pace |first=M. L. |coauthors=Cole, J. J.; et al. |year=1999 |month=December |title=Trophic cascades revealed in diverse ecosystems |journal=Trends in Ecology and Evolution |volume=14 |issue=12 |pages=483-488 |url= http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&list_uids=10542455&cmd=Retrieve&indexed=google |accessdate= 2007-11-24]
List of Apex Predators
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