Triumph displays inform eavesdropping little blue penguins of new dominance asymmetries

Agonistic signals used during contests over important resources have been extensively studied; post-conflict signals have received comparatively little attention. While ‘triumph displays’, performed by winners following fights, have been described for many species, no experiment has yet assessed one of the main hypotheses explaining their existence: advertising victory to social eavesdroppers. Our experiments evaluated the impact of triumph calls on the behaviour and stress responses of surrounding penguins. We found that territorial male little blue penguins, Eudyptula minor, having previously been exposed to playback of a vocal exchange between conspecifics followed by the sounds of a fight, had higher heart rates in response to the winner’s call than that of the loser; females had high rates in response to both winners and losers. Males were also less likely to threaten winners than losers vocally during a simulated approach of their burrow, while females remained silent in both contexts. Our findings support the hypothesis that triumph calls facilitate an association of winners’ distinctive vocalizations with stress generated by nearby overt aggression. By advertising their victories, males may establish a ‘reputation’ for winning fights within the social group, potentially reducing the likelihood of being challenged by eavesdroppers in future contests

Everyday bat vocalizations contain information about emitter, addressee, context, and behavior

Animal vocal communication is often diverse and structured. Yet, the information concealed in animal vocalizations remains elusive. Several studies have shown that animal calls convey information about their emitter and the context. Often, these studies focus on specific types of calls, as it is rarely possible to probe an entire vocal repertoire at once. In this study, we continuously monitored Egyptian fruit bats for months, recording audio and video around-the-clock. We analyzed almost 15,000 vocalizations, which accompanied the everyday interactions of the bats, and were all directed toward specific individuals, rather than broadcast. We found that bat vocalizations carry ample information about the identity of the emitter, the context of the call, the behavioral response to the call, and even the call’s addressee. Our results underline the importance of studying the mundane, pairwise, directed, vocal interactions of animals

The vocal repertoire of the domesticated zebra finch: a data-driven approach to decipher the information-bearing acoustic features of communication signals

Although a universal code for the acoustic features of animal vocal communication calls may not exist, the thorough analysis of the distinctive acoustical features of vocalization categories is important not only to decipher the acoustical code for a specific species but also to understand the evolution of communication signals and the mechanisms used to produce and understand them.Here, we recorded more than 8,000 examples of almost all the vocalizations of the domesticated Zebra finch, Taeniopygia guttata: vocalizations produced to establish contact, to form and maintain pair bonds, to sound an alarm, to communicate distress or to advertise hunger or aggressive intents. We characterized each vocalization type using complete representations that avoided any a priori assumptions on the acoustic code, as well as classical bioacoustics measures that could provide more intuitive interpretations. We then used these acoustical features to rigorously determine the potential information-bearing acoustical features for each vocalization type using both a novel regularized classifier and an unsupervised clustering algorithm. Vocalization categories are discriminated by the shape of their frequency spectrum and by their pitch saliency (noisy to tonal vocalizations) but not particularly by their fundamental frequency. Notably, the spectral shape of zebra finch vocalizations contains peaks or formants that vary systematically across categories and that would be generated by active control of both the vocal organ (source) and the upper vocal tract (filter)