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Shallow and deep lunge feeding of humpback whales in fjords of the West Antarctic Peninsula

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Abstract

Humpback whales (Megaptera novaeangliae) belong to the class of marine mammals known as rorquals that feed through extraordinarily energetic lunges during which they engulf large volumes of water equal to as much as 70% of their body mass. To understand the kinematics of humpback lunge feeding, we attached high-resolution digital recording tags incorporating accelerometers, magnetometers, pressure and sound recording to whales feeding on euphausiids in fjords of the West Antarctic Peninsula. Instances of near vertical lunges gave us the unique opportunity to use the signal from the accelerometer to obtain a fine scale record of the body accelerations involved in lunging. We found that lunges contain extreme accelerations reaching 2.5 m/s2 in certain instances, which are then followed by decelerations. When animals are intensively feeding the inter-lunge interval is similar for both deep and shallow lunges suggesting a biomechanical constraint on lunges. However, the number of lunges per dive varies from one for shallow feeding (<25 m) to a median of six for deeper dives. Different feeding patterns were evident in the kinematic record, for deep and shallow feeding bouts with the much greater mean turn rates occurring in shallow feeding.

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Ancillary