Authors: Wiley, David¹; Ware, Colin²; Bocconcelli, Alessandro³; Cholewiak, Danielle⁴; Friedlaender, Ari⁵; Thompson, Michael⁴; Weinrich, Mason⁶

Source: Behaviour, Volume 148, Numbers 5-6, 2011 , pp. 575-602(28)

Publisher: BRILL

Abstract:

Humpback whales (Megaptera novaeangliae) employ a unique and complex foraging behaviour — bubble-netting — that involves expelling air underwater to form a vertical cylinder-ring of bubbles around prey. We used digital suction cup tags (DTAGs) that concurrently measure pitch, roll, heading, depth and sound (96 kHz sampling rate), to provide the first depiction of the underwater behaviours in which humpback whales engage during bubble-net feeding. Body mechanics and swim paths were analysed using custom visualization software that animates the underwater track of the whale and quantifies tag sensor values. Bubble production was identified aurally and through spectrographic analysis of tag audio records. We identified two classes of behaviour (upward-spiral; 6 animals, 118 events and double-loop; 3 animals, 182 events) that whales used to create bubble nets. Specifically, we show the actual swim path of the whales (e.g., number of revolutions, turning rate, depth interval of spiral), when and where in the process bubbles were expelled and the pattern of bubble expulsion used by the animals. Relative to other baleanopterids, bubble-netting humpbacks demonstrate increased manoeuvrability probably aided by a unique hydrodynamicly enhanced body form. We identified an approximately 20 m depth or depth interval limit to the use of bubble nets and suggest that this limit is due to the physics of bubble dispersal to which humpback whales have behaviourally adapted. All animals were feeding with at least one untagged animal and we use our data to speculate that reciprocity or by-product mutualism best explain coordinated feeding behaviour in humpbacks.

Keywords: HUMPBACK WHALE; FEEDING; BUBBLE NET; KINEMATIC; SPIRAL-LOOP; DOUBLE-LOOP

Document Type: Research article

DOI: http://dx.doi.org/10.1163/000579511X570893

Affiliations: 1: Stellwagen Bank National Marine Sanctuary, NOAA National Ocean Service, 175 Edward Foster Road, Scituate, MA 02066, USA;, Email: David.Wiley@noaa.gov 2: Centre for Coastal and Ocean Mapping, University of New Hampshire, 24 Colovos Road, Durham, NH 03824, USA 3: Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, USA 4: Stellwagen Bank National Marine Sanctuary, NOAA National Ocean Service, 175 Edward Foster Road, Scituate, MA 02066, USA 5: Duke University Marine Laboratory, 135 Pivers Island Road, Beaufort, NC 28516, USA 6: Whale Centre of New England, 24 Harbour Loop Road, Gloucester, MA 01931, USA

Publication date: 2011-06-01

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• In this Subject: Biology/Life Sciences ,  Zoology ,  Ecology
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