Validation of a device for accurate timing of feeding events in marine animals

Two acceleration data loggers, each measuring surging and heaving acceleration, were attached to the head and mandible of three captive hooded seals, Cystophora cristata, for detection of underwater feeding events. Three sizes of prey: Atlantic herring (large), capelin (medium), and half a capelin (small) were tested. A highpass frequency-filtering method at 3 Hz provided more distinct prey ingestion signals for both head and mandible acceleration. The surge-axis signals from head acceleration suggested that the seals ingested their prey not only by biting, but also by thrusting. Moreover, prey ingestion movements showed higher surging acceleration from mandible than from head (mean +/- A SD from head: 5.37 +/- A 4.45 m s(-2), from mandible: 8.43 +/- A 5.15 m s(-2), n = 153), indicating that the data from the head is not required for precise identification of feeding events. Thus, our mandible acceleration device provides a practical method for the timing of underwater feeding events in seals.