Fine-scale feeding behavior of Weddell seals revealed by a mandible accelerometer

We used a mandible accelerometer to document feeding events in two free-ranging adult female Weddell seals in Atka Bay, Antarctica. Using spectral analysis, we isolated several patterns in the mandible acceleration data. The shorter, un-attenuated signals are thought to represent feeding. The longer, attenuating signals are thought to represent vocalizing activities. The depth data suggest that one seal dived under the base of the iceberg. During these dives we detected a unique type of feeding signal. These signals were characterized by patterns of low amplitude and irregular peaks. A second signal type, characterized by a larger amplitude, was observed 75 times at depths shallower than 60 m. The number of feeding signals per dive was higher for iceberg associated dives (>60 m, 11.3 signals/dive) than for dives to midwater depths (<60 m, 0.5 signals/dive). Our results support the hypothesis that underwater surface of icebergs serves as a habitat for marine fauna. We recorded the first vocalization related signals in seals using a mandible accelerometer. One seal spent significantly more time in shallow water and foraged less than the second seal. This seal also vocalized more often (135 events) than the second individual (29 events), possibly due to an emphasis on mating behavior.