In many terrestrial species, there is a relationship between the acoustic features of vocal signals and the underlying motivational state and arousal level of the signaller. This information may be particularly important during complex social interactions, which are common in species where males compete for access to females during the breeding season. However, research into how information on motivation and arousal is used in marine mammals during these interactions is limited. Here, we examined changes in the calling behaviour of humpback whale (Megaptera novaeangliae) female-calf groups with the addition of escorts to investigate if and how potential information on motivation and arousal is encoded within their non-song vocal signals. Female-calf pairs had low overall call rates and used primarily single calls. However, the addition of one or more escorts to the group resulted in a significant increase in individual call rates, the use of long bouts of calls, and a more variable vocal repertoire. These results indicate that humpback whales convey both motivation and arousal by modifying various features of call production, as well as using specific call types, which contributes to our growing understanding of their complex communication system.
Acoustic communication, arousal, motivation, vocalisations, vocal repertoire