Humpback whale social sounds
Though the songs of humpback whales have been studied extensively for many years, research into their other communicative sounds (known collectively as 'social sounds') is fairly new. Humpback whale social sounds comprise two types of sound; sounds produced by surface behaviours (such as breaching or slapping the surface) and vocal calls.
unds has been on the east Australian population during their southern migration. The catalogue of vocal sounds they use is extremely varied, comprising of at least 34 different sound types ranging from low frequency 'snort'-like sounds to high frequency 'bird chirp'-like sounds (Dunlop et al. 2007). Vocal sounds, as well as surface-generated sounds, are thought to be used in many different contexts; as song-like signals may be used for sexual selection, other signals may be used to maintain contact between group members (such as cows with calves), to provide information on sex and location of the signaller and/or to mediate competition between males. Initial work into the contextual use of these sounds (e.g. Dunlop et al. 2008) has provided many testable hypotheses but much more work is needed to elucidate the specific function of each sound type
Much of the research into large whale communication centres on the effects of anthropogenic noise. However, before understanding the effects of anthropogenic noise on their communication, we must first understand how they communicate in ‘natural’ noise. A recent study found that humpback whales tend to change from primarily vocal communication to primarily surface-generated sound production in higher wind-dominated noise levels (Dunlop et al. 2010) as well as increase their vocal level (Dunlop et al. 2014). In response to a temporary increase in background noise due to passing vessels, humpback whales did neither (Dunlop 2016a). However, the presence of nearby singers has also been found to have a significant effect on vocal behaviour (Dunlop 2016b). Therefore, both the noise environment and the social environment have complex effects on humpback whale communication behaviour (Project leader: Rebecca Dunlop).
Humpback whale social sounds are also the subject of research by PhD student Kate Indeck, who began her PhD in 2015. She is currently working to establish the social sound repertoire of mother/calf pairs during migration, and will use this foundational data to examine the context of mother/calf sound production. She is further interested in determining the effects of both the social and the noise environments on their vocal behaviour. New PhD student Dana Cusano (beginning her PhD in July 2016) will join the social sounds research team, focusing her work on the types of social vocalisations used within competitive groups. She will also investigate the potential use of encoded cues that include emotional and motivational information. Previous work was conducted by Mindi Rekdahl, who completed her PhD in 2010.