Head and Whisker Behaviours Observed During Foraging in Northern Elephant Seals (Mirounga angustirostris)

Pinnipeds use their whiskers to detect and follow hydrodynamic cues during foraging. The movement of their head and whiskers is likely to be important for positioning the whiskers towards salient points in the flow-scape. We present here the first descriptions of whisker and head movements in freely moving, foraging male northern elephant seals (Mirounga angustirostris) using a novel, non-invasive underwater filming set-up. We observed a range of behaviours during foraging, including forward swimming, vertical diving, diving with rotations, swooping swimming motions, vertical head dabbing (or bobbing), and lateral head sweeping, which occurred at different timescales, ranging from long, continuous swims to 0.4 s dabs. These different types of movements in time and space likely provide the seals with the range of head and whisker positions and timings necessary for successful foraging. We also observed prolonged whisker protractions and rhythmic whisker movements with amplitudes of 10°-130°. These are the largest ever measured in pinnipeds. It is likely that only by observing naturalistic behaviours, such as foraging in the wild, can these large, full whisker movements be observed. With this in mind, continuing to develop technology to observe naturalistic whisker movements in the field will give us better insights into the sensory behaviours of pinnipeds and other mammals.