Predator satiation

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Predator satiation has evolved as a reproductive pattern in cicadas of the genus Magicicada.[1]

Predator satiation (less commonly called predator saturation) is an antipredator adaptation in which prey occur at high population densities, reducing the probability of an individual organism being eaten.[2] When predators are flooded with potential prey, they can consume only a certain amount, so by occurring at high densities prey benefit from a safety in numbers effect. This strategy has evolved in a diverse range of prey, from trees to insects. Predator satiation can be considered a type of refuge from predators.[2]

As available food increases, a predator has more chances of survival, growth, and reproduction.[3] However, as food supply begins to overwhelm the predator's ability to consume and process it, consumption levels off. This pattern is evident in the functional response of type II. There are also limits to population growth (numerical response), dependent on the generation time of the predator species.

This phenomenon is particularly conspicuous when it takes the form of masting, the production of large numbers of seeds by a population of plants.

Some periodical cicada (Magicicada) species erupt in large numbers from their larval stage at intervals in years that are prime numbers, 13 or 17. At high density sites, research finds that the number eaten by birds does not increase with the number of cicada individuals and the risk of predation for each individual decreases.[4]

In contrast to predator satiation, a different pattern is seen in response to mutualistic consumers, which benefit an organism by feeding from it (such as frugivores, which disperse seeds). For example, a vine's berries may ripen at different times, ensuring frugivores are not swamped with food and so resulting in a larger proportion of its seeds being dispersed.

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References[edit]

  1. ^ Williams, K. S.; Smith, K. G. & Stephen, F. M. (1 June 1993). "Emergence of 13-year periodical cicadas (Cicacidae: Magicicada): phenology, mortality and predator satiation". Ecology 74 (4): 1143–1152. doi:10.2307/1940484. ISSN 0012-9658. JSTOR 1940484. 
  2. ^ a b Molles, Manuel C., Jr. (2002). Ecology: Concepts and Applications (International ed.). New York: The McGraw-Hill Companies, Inc. pp. 586 pp. ISBN 0-07-112252-4. 
  3. ^ Begon, M., J.L. Harper and C.R. Townsend. 1996. Ecology: individuals, populations, and communities, Third Edition. Blackwell Science Ltd., Cambridge, Massachusetts, USA.
  4. ^ Karban, Richard (April 1982). "Increased Reproductive Success at High Densities and Predator Satiation For Periodical Cicadas". Ecology 63 (2): 321–328. doi:10.2307/1938949. JSTOR 1938949.