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| Author |
Van Doorn G.S.; Hengeveld G.M.; Weissing F.J. |
| Title |
The Evolution of Social Dominance I: Two-player Models |
Type |
Journal Article |
| Year |
2003 |
Publication |
Behavior |
Abbreviated Journal |
Behavior |
| Volume |
140 |
Issue |
10 |
Pages |
1305-1332 |
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| Abstract |
A difference in dominance rank is an often-used cue to resolve conflicts between two animals without escalated fights. At the group level, adherence to a dominance convention efficiently reduces the costs associated with conflicts, but from an individual's point of view, it is difficult to explain why a low ranking individual should accept its subordinate status. This is especially true if, as suggested by several authors, dominance not necessarily reflects differences in fighting ability but rather results from arbitrary historical asymmetries. According to this idea, rank differentiation emerges from behavioural strategies, referred to as winner and loser effects, in which winners of previous conflicts are more likely to win the current conflict, whereas the losers of previous conflicts are less likely to do so. In order to investigate whether dominance, based on such winner and loser effects, can be evolutionarily stable, we analyse a game theoretical model. The model focuses on an extreme case in which there are no differences in fighting ability between individuals at all. The only asymmetries that may arise between individuals are generated by the outcome of previous conflicts. By means of numerical analysis, we find alternative evolutionarily stable strategies, which all utilize these asymmetries for conventional conflict resolution. One class of these strategies is based on winner and loser effects, thus generating evolutionarily stable dominance relations even in the absence of differences in resource holding potential. |
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Equine Behaviour @ team @ |
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5105 |
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| Author |
Van Doorn G.S.; Hengeveld G.M.; Weissing F.J. |
| Title |
The Evolution of Social Dominance II: Multi-Player Models |
Type |
Journal Article |
| Year |
2003 |
Publication |
Behavior |
Abbreviated Journal |
Behavior |
| Volume |
140 |
Issue |
10 |
Pages |
1333-1358 |
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| Abstract |
The social hierarchies observed in natural systems often show a high degree of transitivity. Transitive hierarchies do not only require rank differentiation within pairs of individuals but also a higher level ordering of relations within the group. Several authors have suggested that the formation of linear hierarchies at the group level is an emergent property of individual behavioural rules, referred to as winner and loser effects. Winner and loser effects occur if winners of previous conflicts are more likely to escalate the current conflict, whereas the losers of previous conflicts are less likely to do so. According to this idea, an individual's position in a hierarchy may not necessarily reflect its fighting ability, but may rather result from arbitrary historical asymmetries, in particular the history of victories and defeats. However, if this is the case, it is difficult to explain from an evolutionary perspective why a low ranking individual should accept its subordinate status. Here we present a game theoretical model to investigate whether winner and loser effects giving rise to transitive hierarchies can evolve and under which conditions they are evolutionarily stable. The main version of the model focuses on an extreme case in which there are no intrinsic differences in fighting ability between individuals. The only asymmetries that may arise between individuals are generated by the outcome of previous conflicts. We show that, at evolutionary equilibrium, these asymmetries can be utilized for conventional conflict resolution. Several evolutionarily stable strategies are based on winner and loser effects and these strategies give rise to transitive hierarchies. |
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Equine Behaviour @ team @ |
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5106 |
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Dyer, J.R.G.; Johansson, A.; Helbing, D.; Couzin, I.D.; Krause, J. |
| Title |
Leadership, consensus decision making and collective behaviour in humans |
Type |
Journal Article |
| Year |
2009 |
Publication |
Philosophical Transactions of the Royal Society B: Biological Sciences |
Abbreviated Journal |
Phil. Trans. Biol. Sci. |
| Volume |
364 |
Issue |
1518 |
Pages |
781-789 |
| Keywords |
* leadership * consensus decision making * collective behaviour * human group |
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This paper reviews the literature on leadership in vertebrate groups, including recent work on human groups, before presenting the results of three new experiments looking at leadership and decision making in small and large human groups. In experiment 1, we find that both group size and the presence of uninformed individuals can affect the speed with which small human groups (eight people) decide between two opposing directional preferences and the likelihood of the group splitting. In experiment 2, we show that the spatial positioning of informed individuals within small human groups (10 people) can affect the speed and accuracy of group motion. We find that having a mixture of leaders positioned in the centre and on the edge of a group increases the speed and accuracy with which the group reaches their target. In experiment 3, we use large human crowds (100 and 200 people) to demonstrate that the trends observed from earlier work using small human groups can be applied to larger crowds. We find that only a small minority of informed individuals is needed to guide a large uninformed group. These studies build upon important theoretical and empirical work on leadership and decision making in animal groups. |
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Equine Behaviour @ team @ |
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5122 |
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Harcourt, J.L.; Ang, T.Z.; Sweetman, G.; Johnstone, R.A.; Manica, A. |
| Title |
Social feedback and the emergence of leaders and followers |
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Journal Article |
| Year |
2009 |
Publication |
Current Biology : CB |
Abbreviated Journal |
Curr Biol |
| Volume |
19 |
Issue |
3 |
Pages |
248-252 |
| Keywords |
Analysis of Variance; Animals; Appetitive Behavior/physiology; *Feedback; Great Britain; *Leadership; Markov Chains; Models, Biological; Monte Carlo Method; Smegmamorpha/*physiology; *Social Behavior; Video Recording |
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In many animal groups, certain individuals consistently appear at the forefront of coordinated movements [1-4]. How such leaders emerge is poorly understood [5, 6]. Here, we show that in pairs of sticklebacks, Gasterosteus aculeatus, leadership arises from individual differences in the way that fish respond to their partner's movements. Having first established that individuals differed in their propensity to leave cover in order to look for food, we randomly paired fish of varying boldness, and we used a Markov Chain model to infer the individual rules underlying their joint behavior. Both fish in a pair responded to each other's movements-each was more likely to leave cover if the other was already out and to return if the other had already returned. However, we found that bolder individuals displayed greater initiative and were less responsive to their partners, whereas shyer individuals displayed less initiative but followed their partners more faithfully; they also, as followers, elicited greater leadership tendencies in their bold partners. We conclude that leadership in this case is reinforced by positive social feedback. |
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Department of Zoology, University of Cambridge, Cambridge, UK |
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English |
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0960-9822 |
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PMID:19185497 |
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no |
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Equine Behaviour @ team @ |
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5123 |
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King, A.J.; Douglas, C.M.S.; Huchard, E.; Isaac, N.J.B.; Cowlishaw, G. |
| Title |
Dominance and affiliation mediate despotism in a social primate |
Type |
Journal Article |
| Year |
2008 |
Publication |
Current Biology : CB |
Abbreviated Journal |
Curr Biol |
| Volume |
18 |
Issue |
23 |
Pages |
1833-1838 |
| Keywords |
Animals; *Authoritarianism; Behavior, Animal/*physiology; Cooperative Behavior; *Decision Making; Feeding Behavior; Female; *Group Processes; Male; Papio ursinus/*psychology; *Social Dominance |
| Abstract |
Group-living animals routinely have to reach a consensus decision and choose between mutually exclusive actions in order to coordinate their activities and benefit from sociality. Theoretical models predict “democratic” rather than “despotic” decisions to be widespread in social vertebrates, because they result in lower “consensus costs”-the costs of an individual foregoing its optimal action to comply with the decision-for the group as a whole. Yet, quantification of consensus costs is entirely lacking, and empirical observations provide strong support for the occurrence of both democratic and despotic decisions in nature. We conducted a foraging experiment on a wild social primate (chacma baboons, Papio ursinus) in order to gain new insights into despotic group decision making. The results show that group foraging decisions were consistently led by the individual who acquired the greatest benefits from those decisions, namely the dominant male. Subordinate group members followed the leader despite considerable consensus costs. Follower behavior was mediated by social ties to the leader, and where these ties were weaker, group fission was more likely to occur. Our findings highlight the importance of leader incentives and social relationships in group decision-making processes and the emergence of despotism. |
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Institute of Zoology, Zoological Society of London, Regent's Park, London, NW1 4RY, UK. andrew.king@ioz.ac.uk |
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English |
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0960-9822 |
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PMID:19026539 |
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Equine Behaviour @ team @ |
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5124 |
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Rands, S.A.; Cowlishaw, G.; Pettifor, R.A.; Rowcliffe, J.M.; Johnstone, R.A. |
| Title |
The emergence of leaders and followers in foraging pairs when the qualities of individuals differ |
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Journal Article |
| Year |
2008 |
Publication |
BMC Evolutionary Biology |
Abbreviated Journal |
BMC Evol Biol |
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8 |
Issue |
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Pages |
51 |
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Animals; *Feeding Behavior; *Food Chain; *Models, Biological; *Social Dominance |
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BACKGROUND: Foraging in groups offers animals a number of advantages, such as increasing their likelihood of finding food or detecting and avoiding predators. In order for a group to remain together, there has to be some degree of coordination of behaviour and movement between its members (which may in some cases be initiated by a decision-making leader, and in other cases may emerge as an underlying property of the group). For example, behavioural synchronisation is a phenomenon where animals within a group initiate and then continue to conduct identical behaviours, and has been characterised for a wide range of species. We examine how a pair of animals should behave using a state-dependent approach, and ask what conditions are likely to lead to behavioural synchronisation occurring, and whether one of the individuals is more likely to act as a leader. RESULTS: The model we describe considers how the energetic gain, metabolic requirements and predation risks faced by the individuals affect measures of their energetic state and behaviour (such as the degree of behavioural synchronisation seen within the pair, and the value to an individual of knowing the energetic state of its colleague). We explore how predictable changes in these measures are in response to changes in physiological requirements and predation risk. We also consider how these measures should change when the members of the pair are not identical in their metabolic requirements or their susceptibility to predation. We find that many of the changes seen in these measures are complex, especially when asymmetries exist between the members of the pair. CONCLUSION: Analyses are presented that demonstrate that, although these general patterns are robust, care needs to be taken when considering the effects of individual differences, as the relationship between individual differences and the resulting qualitative changes in behaviour may be complex. We discuss how these results are related to experimental observations, and how the model and its predictions could be extended. |
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Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK. sean.rands@bristol.ac.uk |
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English |
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1471-2148 |
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PMID:18282297 |
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no |
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Equine Behaviour @ team @ |
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5126 |
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Rands, S.A.; Cowlishaw, G.; Pettifor, R.A.; Rowcliffe, J.M.; Johnstone, R.A. |
| Title |
Spontaneous emergence of leaders and followers in foraging pairs |
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Journal Article |
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2003 |
Publication |
Nature |
Abbreviated Journal |
Nature |
| Volume |
423 |
Issue |
6938 |
Pages |
432-434 |
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Animals; *Energy Metabolism; Food; *Food Chain; *Models, Biological; Motor Activity; *Social Behavior; Time Factors |
| Abstract |
Animals that forage socially often stand to gain from coordination of their behaviour. Yet it is not known how group members reach a consensus on the timing of foraging bouts. Here we demonstrate a simple process by which this may occur. We develop a state-dependent, dynamic game model of foraging by a pair of animals, in which each individual chooses between resting or foraging during a series of consecutive periods, so as to maximize its own individual chances of survival. We find that, if there is an advantage to foraging together, the equilibrium behaviour of both individuals becomes highly synchronized. As a result of this synchronization, differences in the energetic reserves of the two players spontaneously develop, leading them to adopt different behavioural roles. The individual with lower reserves emerges as the 'pace-maker' who determines when the pair should forage, providing a straightforward resolution to the problem of group coordination. Moreover, the strategy that gives rise to this behaviour can be implemented by a simple 'rule of thumb' that requires no detailed knowledge of the state of other individuals. |
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Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK. s.rands@zoo.cam.ac.uk |
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English |
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0028-0836 |
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PMID:12761547 |
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Equine Behaviour @ team @ |
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5138 |
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Camazine, S.; Deneubourg, J.L.; Franks, N.R.; Sneyd, J.; Theraula, G.; Bonabeau, E. |
| Title |
Self-Organization in Biological Systems |
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Book Whole |
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2003 |
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Princeton University Press |
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Princeton |
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978-0691116242 |
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Equine Behaviour @ team @ |
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5143 |
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Schaller, G.B: |
| Title |
The Mountain Gorilla: Ecology and Behaviour. |
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Journal Article |
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1964 |
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Oryx |
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7 |
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05 |
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253-254 |
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Cambridge Journals Online |
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Cambridge |
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Zuckerman, S |
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0030-6053 |
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Equine Behaviour @ team @ |
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5149 |
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Smith, L.A.; Wells, K.L.; Marion, G.; Swain, D.L.; Hutchings, M.R. |
| Title |
Effects of group composition on the grazing behaviour of herbivores |
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Journal Article |
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Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
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In Press, Corrected Proof |
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grazing; group composition; herbivore; individual behaviour; physiological state |
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Animal behaviour is often a function of the animal's physiological state. Groups of animals will often contain individuals with a range of physiological states and the grazing behaviour of herbivores is affected by their physiological state. This study compared the grazing decisions of animals in groups of single and mixed physiological states. Using a grazing model that simulated individual herbivore behaviour in relation to environmental distributions of forage resource (grass) and parasites (faeces), we tested the hypothesis that an animal's level of parasite exposure via the faecal-oral route is affected by the composition of physiological states in the group. Four physiological states were considered: parasite-naïve, parasitized, lactating and parasite-immune animals. Baseline parasite exposure levels for each state were generated by simulating single-state groups and were compared to simulations of each of the six two-state combinations. In single-state groups parasitized animals had the least and lactating animals had the greatest levels of parasite exposure. When co-grazing with lactating animals, parasitized, immune and naïve animals increased their parasite exposure, relative to single-state groups. When co-grazing with parasitized animals, lactating, immune and naïve animals reduced their parasite exposure, relative to single-state groups. There was no difference in parasite exposure of the immune or naïve animals co-grazing together when compared to the single-state groups. These results highlight the need to recognize the impact of the individual when studying group-living animals. |
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0003-3472 |
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Equine Behaviour @ team @ |
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5155 |
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