Predator satiation

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.cite book | last =Molles | first =Manuel C., Jr. | title =Ecology: Concepts and Applications | publisher =The McGraw-Hill Companies, Inc.| edition = International Edition | date =2002 | location =New York | pages =586 pp.| id = ISBN 0-07-112252-4 ] When predators are flooded with potential prey, they can only consume 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.cite book | last =Molles | first =Manuel C., Jr. | title =Ecology: Concepts and Applications | publisher =The McGraw-Hill Companies, Inc.| edition = International Edition | date =2002 | location =New York | pages =p. 340 | id = ISBN 0-07-112252-4 ]

As available food increases, a predator's rates of survival, growth and reproduction increase. [Begon, M., J.L. Harper and C.R. Townsend. 1996. "Ecology: individuals, populations, and communities", Third Edition. Blackwell Science Ltd., Cambridge, Massachusetts, USA.] However, as food supply begins to overwhelm the predator's ability to consume and process it, consumption levels off. This pattern is known as functional response. There are also limits to population growth (numerical response), dependent on the predator species' generation time.

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.cite journal | last =Karban | first =Richard | authorlink = | coauthors = | title =Increased Reproductive Success at High Densities and Predator Satiation For Periodical Cicadas | journal =Ecology | volume = 63 | issue = 2 | pages =pp. 321–328 | publisher = | date =April 1982 | url =http://www.jstor.org/pss/1938949 | doi = | id = | accessdate = 2008-06-22 ]

In contrast to predator satiation, a different pattern is seen in response to mutualistic consumers, which benefit an organism by feeding from it (e.g. 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.

ee also

*Selfish herd
*Semelparity

References