Meeting Abstract
Territorial defense is beneficial to social animals, however individuals within groups may differ in their participation in defense. This could be a consequence of variation in individual ability to provide defense, the relative benefits of providing defense, or the costs associated with particular types of intruders. Further, “powerful” members of groups may be able to influence other group members to modify their response to intruders in such a way to reflect the fitness interests of powerful individuals. We hypothesized that the size and relative size of dominant breeding pairs Neolamprologus pulcher would influence 1) their ability to defend against perceived intruders of the group, and 2) their ability to influence the behavioral response of other group members to intruders. We also hypothesized that size (and relative size) of group members would influence the baseline cortisol levels of individual N. pulcher. To test these hypotheses, we exposed successfully breeding pairs of N. pulcher to three types of intruders, and measured cortisol levels in each fish one week after behavioral trials were complete. Pairs consisted of fish which varied in relative size. Compared to groups in which males were much larger than females, males performed fewer aggressive acts and females performed more aggressive acts towards intruders when males and females were similar in size. Male and female N. pulcher responded less aggressively towards a heterospecific fry predators than they did towards unfamiliar conspecific N. pulcher. There was not a significant relationship between individual cortisol levels and the size (or relative size) of pairs of N. pulcher, or behavioral interactions within the dyad. We conclude that individual phenotype, as well as the interacting phenotypes in groups, can have important consequences for the social dynamics in animal groups.
