Parker GA. Assessment strategy and the evolution of fighting behaviour. J Theor Biol 47: 223-243

Zoology Department, Liverpool University, Liverpool, L69 3BX, England
Journal of Theoretical Biology (Impact Factor: 2.12). 10/1974; 47(1):223-43. DOI: 10.1016/0022-5193(74)90111-8
Source: PubMed


The view is examined that the adaptive value of conventional aspects of fighting behaviour is for assessment of relative RHP (resource holding power) of the combatants. Outcomes of aggressive disputes should be decided by each individual's fitness budget available for expenditure during a fight (determined by the fitness difference between adoption of alternative strategies, escalation or withdrawal without escalation) and on the rate of expenditure of the fitness budget if escalation occurs (determined by the RHPs of the combatants). Thus response thresholds for alternative strategies (“assessments”) will be determined by natural selection on a basis of which opponent is likely to expend its fitness budget first, should escalation occur. This “loser” should retreat (before escalation) and the winner should stay in possession of the resource. Many aggressive decisions depend on whether one is a resource holder, or an attacker. Assuming the RHP of the combatants to be equal, there are many instances of fitness pay-off imbalances between holder and attacker which should weight the dispute outcome in favour of one or other opponent by allowing it a greater expendable fitness budget. Usually the weighting favours the holder; the attacker therefore needs a correspondingly higher RHP before it may be expected to win. This is not invariably the case, and much observed data fits the predictions of this sort of model. If assessments are perfect and budget expenditure rates exactly predictable, then there would never seem to be any case for escalation. Escalation can be explained in terms of injury inflictions (expenditures) occurring as discrete events; i.e. as “bouts” won or lost during fighting. Assessment can give only a probabilistic prediction of the outcome of a bout. A simple model is developed to investigate escalation situations. Each combatant assesses relative RHP; this correlates with an absolute probability of winning the next bout (cabs). The stake played for is infliction of loss of RHP and is determined by the fitness budgets of the opponents. (Each individual plays for the withdrawal of its opponent.) This defines a critical probability of winning (ccrit) for each combatant, above which escalation is the favourable strategy (cabs > ccrit) and below which withdrawal is favourable (cabs < ccrit). Escalation should occur only where cabs-ccrit is positive for both combatants. This model gives predictions compatible with the observations, indicating that RHP loss alone can be adequate to explain withdrawal: escalation behaviour. Withdrawal tendency will be increased by low searching costs. Escalations should be restricted to closely matched RHP opponents if RHP disparity is the major imbalance. Outside the “escalation range” of a given individual, the higher RHP individual wins and the lower one loses (i.e. it should withdraw after conventional display). RHP disparity and holder: attacker imbalance should both interact to shape the observed pattern, though their relative importances will depend on species and situation. In some instances selection may favour immediate withdrawal from an occupied territory even without assessment of RHP.

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Available from: Geoff A. Parker, Sep 10, 2014
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    • "food or mating partners ), which can lead to increased agonistic interactions between individuals (Alexander, 1974). As aggression can be costly, animals have evolved several strategies to avoid excessive energy expenditure and physical injuries (Parker, 1974), such as the establishment of dominance hierarchies and status signalling. The latter can be an indicator of the opponent's competitive ability, providing decisive information to predict the outcome of a confrontation (Rohwer, 1975) or affect the various stages of agonistic escalation (Chaine & Lyon, 2008; Enquist & Leimar, 1990), which can be particularly relevant in gregarious species, since it can help mediate situations of conflict between members of a group. "
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    ABSTRACT: In gregarious animals, social interactions frequently take the form of dominance hierarchies that maintain stable relationships between individuals, and settle disputes without extra costs. Traits that function as signals of status can play an important role in mediating interactions among individuals, both in social and in sexual contexts. Carotenoid ornaments are more generally assumed to be sexually selected and not so relevant to general social contexts. However, it is possible for them to function in social contexts if they signal socially relevant aspects. Here we experimentally analysed social dominance and resource control in male groups of a gregarious species, the European serin, Serinus serinus, in relation to a sexual ornament. We tested whether yellow carotenoid-based plumage coloration, age, body size and testosterone were predictors of social dominance over a nonsexual resource (i.e. feeding context). We showed that dominance hierarchies were steep and were related to testosterone levels and ornamental coloration, particularly the male yellow carotenoid-based crown patch. Our results suggest that carotenoid-based colour and testosterone levels can be reliable predictors of social status in agonistic encounters in groups of male serins. Moreover, together with previous work on the sexual function of male coloration, this study provides evidence that male serin yellow coloration has a dual function in both sexual and nonsexual contexts. These results raise the possibility that this ornament may have evolved and be maintained via social selection over social competition/cooperation for reproductive opportunities and ecological resources.
    Animal Behaviour 12/2015; 110:155-161. DOI:10.1016/j.anbehav.2015.09.025 · 3.14 Impact Factor
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    • "RESEARCH ARTICLE Journal of Experimental Biology (2015) 218, 3215-3221 doi:10.1242/jeb.125831 provide an honest indication of one's fighting ability (Maynard Smith and Price, 1973; Parker, 1974; Enquist, 1985; Szamado, 2008; Szalai and Szamado, 2009). Threat displays provide clues to the weapons used in fighting; these displays are usually the first step in a species' fighting technique that is used to threaten (Szamado, 2008; Walther, 1984). "

    Journal of Experimental Biology 10/2015; 218(20):3215-3221. DOI:10.1242/jeb.125831 · 2.90 Impact Factor
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    • "These results , as well as the duration of the contests , are in accordance with cuttlefish contests in the field ( Hall & Hanlon , 2002 ) . For many taxa , the outcome of animal contests is influenced by body size ( Haley , Deutsch , & Le Boeuf , 1994 ; Wells , 1988 ) because this attribute is generally correlated with strength and the ability to inflict injury ( Archer , 1988 ; Parker , 1974 ) . For example , in mantis shrimp , Gonodactylaceus falcatus , larger in - dividuals have a physical advantage over smaller individuals because both spring and strike force of the raptorial attack are correlated positively with body size ( Claverie , Chan , & Patek , 2011 ) . "
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    ABSTRACT: Game theory models provide a useful framework for investigating strategies of conflict resolution in animal contests. Model predictions are based on estimates of resource-holding potential (RHP) and vary in their assumptions about how opponents gather information about RHP. Models can be divided into self-assessment strategies (energetic war-of-attrition, E-WOA; cumulative assessment model, CAM) and mutual assessment strategies (sequential assessment model, SAM). We used laboratory-staged contests between male giant Australian cuttlefish, Sepia apama, to evaluate RHP traits and to test game theory models. Mantle length was a key indicator of RHP because it predicted contest outcome, whereby larger individuals were more likely to win a contest. Winners and losers did not match behaviours, ruling out the E-WOA. There was no relationship between contest outcome, duration and escalation rates, arguing against the CAM. Persistence to continue a contest was based on RHP asymmetry, rather than loser and/or winner RHP, providing support for the SAM. Motivation to fight was determined from a male's latency to resume a contest following the introduction of a female during a contest. The latency to resume a contest was negatively related to the size of the focal male and positively related to the size of their opponent. These results show that competing males are able to gather information concerning RHP asymmetries, providing support for mutual assessment. Furthermore, males showed significant behavioural differences in their responses to relatively larger than to relatively smaller opponents. Using an integrative approach, our study provides a well-substantiated example of mutual assessment.
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