The role of vocal individuality in conservation.

Identifying the individuals within a population can generate information on life history parameters, generate input data for conservation models, and highlight behavioural traits that may affect management decisions and error or bias within census methods. Individual animals can be discriminated by features of their vocalisations. This vocal individuality can be utilised as an alternative marking technique in situations where the marks are difficult to detect or animals are sensitive to disturbance. Vocal individuality can also be used in cases were the capture and handling of an animal is either logistically or ethically problematic. Many studies have suggested that vocal individuality can be used to count and monitor populations over time; however, few have explicitly tested the method in this role. In this review we discuss methods for extracting individuality information from vocalisations and techniques for using this to count and monitor populations over time. We present case studies in birds where vocal individuality has been applied to conservation and we discuss its role in mammals.

Information and aggression in fishes.

Aggressive interactions between fishes commonly take place in a social environment in which uninvolved individuals (bystanders) have an opportunity to gather information about interactants. Signals frequently used during such interactions are designed to transmit information about resource-holding power and/or intention. They are generally related to the level of escalation reached and the eventual outcome of a fight. We consider here the information available in signaling and nonsignaling aspects of aggressive interactions. We focus, in particular, on information available to bystanders. We summarize evidence that bystanders alter their behavior toward interactants on the basis of information acquired while bystanding, and we discuss the sources of information that may result in this change of behavior. In particular, we distinguish eavesdropping (i.e., extracting information from signaling interactions) as a subset of bystanding (i.e., extracting information from all available sources). We conclude that considerations of aggressive strategies should include potential costs and benefits resulting from wider social contexts in which aggression occurs.

Timing of presentation of an audience: aggressive priming and audience effects in male displays of Siamese fighting fish (Betta splendens).

Studies of animal communication often underestimate the presence of individuals other than the signaller-receiver dyad. Signalling interactions often occur in the presence of non-participating individuals (audiences); the effect of these individuals upon the dynamics of interactions has been called the audience effect. Recent studies of fighting fish Betta splendens have shown that the presence of a male audience can increase aggression during interactions. However, in many of these studies males were allowed to see the audience prior to the interaction, thus such pre-exposure may have facilitated aggressive behaviour (aggressive priming). Here we present results of two experiments designed to examine the relative importance of priming and audience effects on the dynamics of aggressive interactions. Males that were pre-exposed showed higher levels of aggression during subsequent interactions regardless of the presence or absence of an audience. When only one of the interactants had been pre-exposed to the audience, the non-exposed male showed similar increases in aggressive behaviour, i.e. matching the level of aggression showed by his opponent. Taken together these results suggest that aggressive priming may have resulted in an over-estimation of the audience effect in previous studies. The results still highlight the importance of social environment in determining the dynamics and outcomes of aggressive contests.