The concept of studying the social interactions of individuals as a network was developed in the social sciences in the first half of the twentieth century. Considering the structure of interactions as a network has provided important new insights into the role of individuals in social systems. For example, by considering how connected individuals were in the population, it was possible to see which individuals might have more influence on the behaviour of others (Scott, 1991). More recently, network theory has received important new impulses from the physics community (see Newman, 2003). In particular, new measures allow us to characterize social structures, both at the level of the individual and the population, and simulation procedures allow statistical rigour to be added to network studies. Surprisingly, the network approach has received relatively little attention in the study of animal behaviour where the emphasis traditionally has been on dyadic relationships. The use of social network analysis potentially provides a major conceptual advance because it allows us to go beyond an investigation of dyadic relationships and views the individual in the context of its group or population (Croft et al., 2008).