Desperado effect

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The desperado effect is an explanatory model that describes the motive behind the attack behavior of animals that seek conflict with stronger conspecifics in a population .

description

In intra-species battles for reproductive possibilities, weaker individuals usually avoid risky battles with stronger conspecifics when it is foreseeable that they will lose the battle. For weak individuals, however, this can mean that they have to avoid all fights and so their expected reproduction rate drops to zero. If there are such asymmetries that would prevent members of a population from reproducing, they are in a desperate position. For lack of alternatives, they subsequently attack stronger conspecifics, although it is very unlikely that they will win the fight. Female individuals can also exhibit this behavior in some species.

The desperado effect is an application of evolutionary game theory .

Origin of the term

The desperado effect was first described in 1987 by Alan Grafen . In his research report from Oxford University , he stated that respecting the asymmetries that can occur due to various characteristics, such as body size, leads to individual individuals in populations always being on the losing side of asymmetry. This could trigger the desperado effect.

Asymmetries

Asymmetries that result from this type of feature are called divisive asymmetry by the counts . They are defined by the fact that at a certain point in life there is no longer any logical possibility for an individual to come back to the winning side of asymmetry. At this point, individuals are often ready to risk time and energy or injury and display aggressive behavior. Young animals that cannot prevail against their older conspecifics do not show the desperado effect, since over time they will take a place on the winning side of the asymmetry anyway. These types of features create an asymmetry that Grafen calls Undivisive Asymmetry .

Individual evidence

  1. ↑ Damian O. Elias, Carlos A. Botero, Maydianne CB Andrade, Andrew C. Mason, Michael M. Kasumovic: High resource valuation fuels “desperado” fighting tactics in female jumping spiders . In: Behavioral Ecology . tape 21 , no. 4 , July 1, 2010, ISSN  1045-2249 , p. 868-875 , doi : 10.1093 / beheco / arq073 ( oxfordjournals.org [accessed May 30, 2016]).
  2. ^ Lesley J. Morrell, Jan Lindström, Graeme D. Ruxton: Why are small males aggressive? In: Proceedings of the Royal Society of London B: Biological Sciences . tape 272 , no. 1569 , June 22, 2005, ISSN  0962-8452 , p. 1235–1241 , doi : 10.1098 / rspb.2005.3085 , PMID 16024387 , PMC 1564107 (free full text) - ( royalsocietypublishing.org [accessed May 30, 2016]).
  3. ^ Alan Grafen: The logic of divisively asymmetric contests: respect for ownership and the desperado effect . In: Animal Behavior . tape 35 , no. 2 , April 1, 1987, pp. 462-467 , doi : 10.1016 / S0003-3472 (87) 80271-3 ( sciencedirect.com [accessed May 30, 2016]).
  4. ↑ Ulrich Müller: Evolution and Game Theory . Ed .: Ulrich Müller. Walter de Gruyter, 1990, ISBN 3-486-82728-6 , p. 196 .