Introduction

Poeciliid fishes such as green swordtails Xiphophorus helleri and guppies Poecilia reticulata aggregate in social groups called shoals. In addition to reducing predation risk and increasing foraging efficiency (e.g. Magurran & Pitcher, 1987; Ranta & Juvonen, 1993), fish shoals promote the transfer of social information within the group. For instance, information about foraging routes is transmitted from trained individuals to naive fish in guppy shoals (Laland & Williams, 1997; Swaney et al., 2001; Brown & Laland, 2002). The type of information transfer demonstrated in the social learning and foraging literature involves the transmission of signals from one or more individuals to the remaining group members. Investigations of social foraging and anti-predator behaviour have demonstrated that poeciliids attend to a variety of cues emitted by both conspecifics and heterospecifics (e.g. predators: Brown & Godin, 1999; Mirza et al., 2001; Brosnan et al., 2003). Although social learning and anti-predator responses constitute important aspects of group living in poeciliids, this chapter focuses more on how individuals gain information from observing interactions that occur in their social environment. Indeed, the concept of communication networks was founded on the premise that the information exchanged during social interactions (e.g. agonistic or courtship displays) may be available not only to the participants but also to bystanders within signal detection range (McGregor, 1993; McGregor et al., 2000).