ASA PRESSROOM

4th ASA/ASJ Joint Meeting, Honolulu, HI

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Look Whos Talking: Humpbacks Dont Just Sing

Rebecca A. Dunlop- r.dunlop@uq.edu.au
School of Veterinary Sci., Univ. of Queensland, St. Lucia, Qld 4072, Australia

Michael J. Noad
School of Veterinary Sci., Univ. of Queensland, St. Lucia, Qld 4072, Australia

Douglas H. Cato
Defence Sci. and Tech Org., Pyrmont, NSW 2009, Australia

Dale Stokes
Scripps Inst. of Oceanogr., La Jolla, CA 92037

Popular version of paper 4pABa4
Presented Friday afternoon, December 1, 2006
4th ASA/ASJ Joint Meeting, Honolulu, HI

Humpback whales are renowned for their long complex songs, only produced by males and probably linked with breeding behaviors. Singing in humpbacks is only part of the acoustic story however. While its been known for a while that humpbacks also produce other brief, unpatterned sounds termed ‘social sounds’, we have found that their social sound ‘vocabulary’ is larger than previously thought. We have also found different social sounds are used in different social and behavioral contexts suggesting that they may be used for a wide range of communicative contexts.

This study was part of the larger HARC (Humpback Acoustic Research Collaboration) project involving researchers from Australia, the US and Britain and funded principally by the US Office of Naval Research. The HARC study site was Peregian Beach, southeast Queensland. It focused on the east Australian population of humpbacks, which migrates annually along the eastern Australian coastline between feeding grounds in the Antarctic and breeding grounds inside the Great Barrier Reef off central and northern Queensland. The southward migration occurs from August to November with a peak in September/October. It is likely that these humpbacks are still in ‘breeding-mode’ even though they are on their way back to the feeding grounds.

Male humpbacks sing both on the breeding grounds and on migration. Numerous studies have been carried out on the function of song and concluded that it is a sexual signal, though to whom it is directed and to what function it serves, remain unanswered. Studies on social sounds in humpbacks, however, are distinctly lacking. These are all non-song sounds produced by humpback whales and can include surface-active behaviors such as breaching or repeated slapping of the tail or fins on the surface of the water, and vocalizations such as ‘wops,’ ‘thwops,’ ‘grumbles,’ ‘snorts,’ ‘cries’ and sounds presumed to be underwater blows.

Photo courtesy: Josh Smith

Social sounds are not as loud as song sounds and so do not propagate as far underwater. This suggests social sounds are directed at animals at comparatively close ranges, that is, animals within the same group or in near-by groups, whereas the song is more likely to be a broadcast signal where the singer is displaying his presence to any whales in the area.

Humpbacks use these social sound communication signals in the breeding grounds, feeding grounds and on migration. Unlike the song, social sounds are not limited to males; females and calves are also making these sounds. They probably convey a wide variety of information such as sender identity (who), sender location (where) and sender context (what). Although we can only speculate on the sender contexts, they are probably used as contact calls between mothers and calves or within groups. They may also be used as social integration calls when two groups join and agonistic calls within large groups, for example when males are competing with each other for access to females. Interestingly, lone animals were found to make these sounds, suggesting their use is not limited social interactions.

Interestingly, humpbacks sometimes use song units (that is specific sounds within the song) as social sounds. We mainly hear this when single males are joining females, suggesting that the sounds within the song (the song units) are important sexual signals, rather than the length or the loudness of the song (as in some bird species). What information the song units convey remains to be seen, but the study of social sounds may serve to answer those persistent questions regarding humpback song; why sing, what is its function and to whom is it directed?

A selection of social sounds, including a recording of each sound, and their possible contextual use.

SOUND TYPE (with sample)	POSSIBLE CONTEXT
breach	many different theories; e.g. location, size,
slapping	female solicitation call i.e. to ‘call-in’ males
wop	mother and calf contact call
thwop	contact call not limited to mother and calf
grumble/snort	within-pod contact call
grunt trains	mediate joins between pods
cry	agonistic
underwater blows	agonistic
song units	sexual signal directed at the female

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