Abstract: Position preferences of well-fed and food-deprived juvenile roach were investigated in schools of 2 and 4 fish in the laboratory. Food-deprived fish appeared significantly more often in the front position than their well-fed conspecifics. For fish at the same hunger level, individuals at the front of the school had the highest feeding rate. These results represent the first evidence for a relationship between the nutritional state of individual fish and their positions in a school and suggest a functional advantage of the preference.

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.

Abstract: Abstract   We present here an attempt to understand behaviors of dominant individuals and of subordinate individuals as behavior strategies in an asymmetric “hawk-dove” game. We assume that contestants have perfect information about relative fighting ability and the value of the resource. Any type of asymmetry, both relevant to and irrelevant to the fighting ability, can be considered. It is concluded that evolutionarily stable strategies (ESSs) depend on the resource value (V), the cost of injury (D), and the probability that the individual in one role will win (x). Different ESSs can exist even when values of V, D, and x are the same. The characteristics of dominance relations detected by observers may result from the ESSs that the individuals are adopting. The model explains some characteristics of dominance relations, for example, the consistent outcome of contests, the rare occurrence of escalated fights, and the discrepancy between resource holding potential (RHP) and dominance relations, from the viewpoint of individual selection.

Abstract: Abstract  SOCPROG is a set of programs which analyses data on animal associations. Data usually come from observations of the social behaviour of individually identifiable animals. Associations among animals, sampling periods, restrictions on the data and association indices can be defined very flexibly. SOCPROG can analyse data sets including 1,000 or more individuals. Association matrices are displayed using sociograms, principal coordinates analysis, multidimensional scaling and cluster analyses. Permutation tests, Mantel and related tests and matrix correlation methods examine hypotheses about preferred associations among individuals and classes of individual. Weighted network statistics are calculated and can be tested against null hypotheses. Temporal analyses include displays of lagged association rates (rates of reassociation following an association). Models can be fitted to lagged association rates. Multiple association measures, including measures produced by other programs such as genetic or range use data, may be analysed using Mantel tests and principal components analysis. SOCPROG also performs mark-recapture population analyses and movement analyses. SOCPROG is written in the programming language MATLAB and may be downloaded free from the World Wide Web.

Abstract: Abstract  Until recently, few studies have used social network theory (SNT) and metrics to examine how social network structure (SNS) might influence social behavior and social dynamics in non-human animals. Here, we present an overview of why and how the social network approach might be useful for behavioral ecology. We first note four important aspects of SNS that are commonly observed, but relatively rarely quantified: (1) that within a social group, differences among individuals in their social experiences and connections affect individual and group outcomes; (2) that indirect connections can be important (e.g., partners of your partners matter); (3) that individuals differ in their importance in the social network (some can be considered keystone individuals); and (4) that social network traits often carry over across contexts (e.g., SN position in male–male competition can influence later male mating success). We then discuss how these four points, and the social network approach in general, can yield new insights and questions for a broad range of issues in behavioral ecology including: mate choice, alternative mating tactics, male–male competition, cooperation, reciprocal altruism, eavesdropping, kin selection, dominance hierarchies, social learning, information flow, social foraging, and cooperative antipredator behavior. Finally, we suggest future directions including: (1) integrating behavioral syndromes and SNT; (2) comparing space use and SNS; (3) adaptive partner choice and SNS; (4) the dynamics and stability (or instability) of social networks, and (5) group selection shaping SNS.