Male alliance formation by north-western Australian Indo-Pacific humpback dolphins?
Krützen, M., Allen, S., Cagnazzi, D., Bejder, L. and Parra, G.J. (2011) Male alliance formation by north-western Australian Indo-Pacific humpback dolphins? In: 19th Biennial Conference on the Biology of Marine Mammals, 27 November - 2 December, Tampa, Florida.
Indo-Pacific humpback dolphins (Sousa chinensis – ‘Sousa’ hereafter) are found in shallow, near-shore waters of the northern Australian coastline. The species’ social structure appears to be characterized by a fission-fusion grouping pattern, similar to that of several other coastal delphinids. Sexual segregation has not been reported. We conducted boat-based photo-identification, biopsy sampling and behavioural surveys of tropical delphinids across northwestern Australia from Coral Bay to Broome between April and July 2010. Here, we provide preliminary evidence that male Sousa across the region form allied pairs. Firstly, there was a high proportion of large, scarred pairs found in close proximity and engaged in coordinated behavior that we tentatively assigned as males based on physical appearance. These preliminary classifications were later proven to be correct by genetic sexing. Secondly, we documented both aggressive and affiliative display behaviors by individuals within putatively allied pairs toward other conspecifics. Thirdly, we recorded instances of object-carrying by individuals within pairs of adult male Sousa around adult female Sousa (a possible socio-sexual display), as well synchronous behavior between suspected male allies in these social settings. Whilst we did not conduct extensive focalindividual or group follows to better document behavior and temporal stabilityof male associations, these preliminary findings suggest an as yet unrecognizedlevel of social complexity in this species.
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|Murdoch Affiliation:||Centre for Fish and Fisheries Research|
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