Distributions of Costs and Benefits Within Groups

Abstract

The previous two chapters described how resources and risk affect the costs and benefits that group members obtain from sociality. However, not all group members necessarily obtain the same benefits, nor do all pay the same costs. The net benefit of group membership is typically skewed in favour of some individuals to the detriment of others. In some cases this skew may be extreme, so that it may pay some group members to leave the group, depending on the opportunities available outside the group. More often, however, all members of the group fare better than they might on their own, even if some do better than others. Furthermore, the benefits and costs are not fixed, so that those that obtain relative low rewards at one point in time may be able to improve their lot subsequently. There are two main predictors of these cost and benefit inequalities within groups: firstly, the position that an animal occupies within a group, relative to other group members, and, secondly, the position an animal occupies within a dominance hierarchy. These factors often interact, with dominant individuals taking up the most favoured positions at the expense of their subordinate social partners. In this chapter, we first examine the payoffs associated with different positions in animal groups; we then examine how animals are able to respond dynamically to these by adjusting their relative position in their group. Finally, we examine the constraints that animals may face on their ability to take up beneficial spatial positions within groups with particular reference to the existence of dominance hierarchies.