Chimpanzees modify recruitment screams as a function of audience composition

Abstract

Wild chimpanzees produce acoustically distinct scream vocalizations depending on their social role during agonistic interactions with other group members. Here, we show that victims during such agonistic interactions alter the acoustic structure of their screams depending on the severity of aggression experienced, providing nearby listeners with important cues about the nature of the attack. However, we also found that victims of severe attacks produced screams that significantly exaggerated the true level of aggression experienced, but they did so only if there was at least one listener in the audience who matched or surpassed the aggressor in rank. Our results are consistent with the more general hypothesis that chimpanzees possess sophisticated understanding of third-party relationships, so-called triadic awareness, and that this knowledge influences their vocal production.audience effect ͉ language evolution ͉ Pan troglodytes ͉ primate vocalizations ͉ social intelligence

Production of food-associated calls in wild male chimpanzees is dependent on the composition of the audience

“…Callers are sensitive to the identity of the individuals surrounding them, and they preferentially produce rough grunts in the presence of important social partners. Our data are consistent with the idea that these calls are directed at particular group members, rather than being indiscriminately broadcast (Slocombe and Zuberbühler 2007;Townsend et al 2008), but further research is needed to establish whether there is a direct causal relationship between the presence of an important social partner and the production of rough grunts.…”

Coalitions in theory and reality: a review of pertinent variables and processes

“…Chimpanzees, for example, may hold out an open hand to another to solicit his or her support, embrace the other, or sit right behind an ally, hooting along with his vocal challenge of the common target (de Waal, 1982). De Waal & van Hooff (1981) provide a detailed analysis of side-directed behaviour in chimpanzees (see also Slocombe & Zuberbühler, 2007), but species-typical recruitment behaviour is also well-known of macaques (e.g., de Waal, 1976;Gouzoules & Gouzoules, 2000), baboons (e.g., Noë, 1990;Cheney et al, 2010), and capuchin monkeys, which encourage each other in a so-called 'overlord', with one coalition partner mounted on the shoulders of the other, while both threaten a common opponent (Perry et al, 2004;Figure 1). All of these behaviours may add to the degree of coordination within the coalition.…”

“…All of these behaviours may add to the degree of coordination within the coalition. Recruitment is moreover very dependent on the identities of the target and the potential supporter, suggesting a good understanding of the relationship network, dubbed 'triadic awareness' (cf., de Waal, 1982), i.e., knowledge of the affiliative and dominance relationships between individuals other than oneself (Perry et al, 2004;Slocombe & Zuberbühler, 2007;Wittig et al, 2014). The fact that many primates have evolved specialized signals for the recruitment of allies strongly suggests the importance of coalitionary synergy, but this idea remains to be tested empirically.…”

The central importance of information in studies of animal communication

“…Hammerschmidt & Fischer 1998). Their acoustic features can also be correlated with different types of aggression (Gouzoules et al 1984), the caller's role in the interaction (Slocombe & Zuberbühler 2005), or the presence of a particular 'audience' (Slocombe & Zuberbühler 2007). As a result, screams used in playback experiments elicit different responses from different individuals, or from the same individual under different circumstances Gouzoules et al 1984;Palombit et al 1997;Fischer 2004;Fugate et al 2008;Slocombe et al 2009).…”