Using multi-sensor suction cup tags to quantify the kinematics of lunge feeding in humpback whales (Megaptera novaeangliae) in the water around the West Antarctic Peninsula.

Abstract

Humpback whales (Megaptera novaeangliae) feed through extraordinarily energetic lunges during which they engulf large volumes of water equal to nearly 70% of their body mass. To understand the kinematics of lunge feeding, we attached high-resolution digital recording tags incorporating accelerometers, magnetometers, pressure and sound recording (Dtag) to whales feeding on euphausiids in fjords on the West Antarctic Peninsula. Instances of near vertical lunges gave us the unique opportunity to correlate the acoustic flow noise recorded on the tag with the signal from the accelerometer and changes in pressure to obtain a fine scale record of the body accelerations involved in lunging. This can then be applied to determine lunging events regardless of body orientation. We found that lunges contain extreme accelerations reaching 2.5 m·s-2 in certain instances, which are then followed by profound decelerations. However, humpback whales appear to differ from balaenopterid whales in the speed at which they are able to accelerate and the fact that they do not come to a complete halt when finishing a lunge. 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 (\u3c25m) to a median of six for deeper dives that reach depths of over 350 meters. 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. Our findings reveal how multi-sensor tag technology can be used to better describe the kinematics of baleen whale feeding and greatly augment our ability to understand their foraging ecology. This knowledge is particularly valuable for understanding how baleen whales in the Southern Ocean affect or may be affected by climate-driven changes in their pre