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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    • "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.
    • "As such, the ability to assess an individual's dominance without having to engage in aggressive competition will spare the less dominant individual potential injuries that could arise from an unsuccessful agonistic encounter (Bernstein, 1981). For women, correctly assessing men's dominance is important for intersexual selection, as dominant men have higher status positions in society (Mueller & Mazur, 1997) and have greater resource acquisition potential (Parker, 1974), both of which could confer benefits to a man's partner (Gangestad & Simpson, 2000). Indeed, women prefer high-status partners (DeWall & Maner, 2008), and therefore, accurate assessments of men's dominance may afford selective advantages in women's mate choice. "
    Perception 08/2015; DOI:10.1177/0301006615596898 · 0.91 Impact Factor
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    • "In recent decades, new data similar to that of the case of James and his neighbor in Fransfontein along with a critical reading of ethnographic literature have led many to question both assumptions. On the one hand, Peterson (1993), Bird-David (1990, 1992, 2005) and Blurton Jones (1984, 1987), building on Parker and Smith (Parker 1974; Smith and Parker 1976; Smith 1974), have provided evidence that food transactions are often solicited by a recipient, rather than generously initiated by the possessor. To account for this, they introduced the terms " demand sharing " (Peterson) and " tolerated theft/scrounging " (Blurton Jones) to make it clear that many transfers are explicitly demanded by a recipient. "
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    ABSTRACT: Two competing models concerning food transfers prominent in the anthropological literature conceptualize such transfers either as sharing or as exchange. Sharing is understood as situational transactions formed through demands and unconditional giving, whereas reciprocal exchange is understood in terms of networking and keeping score. I propose that the picture is more complicated than these classifications suggests. Drawing on data collected in Northwestern Namibia, I show that sharing and reciprocal exchange are dynamically interrelated in actual food transfers. As a local norm, people can demand food from anyone, and they are typically given food in response to a demand. However, in practice, food transfer networks emerge (N = 62) that are highly reciprocal and fit the exchange model much better. Although the sharing norm makes no restrictions on whom to ask, in practice people often turn to their neighbors. Interpersonal dynamics account for why some of those ties become strongly reciprocal and others do not. Under these circumstances, unconditional sharing, a norm that has been viewed as an alternative to exchange, can lead to reciprocity via reciprocity on demand.
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