Remotely releasable instruments for monitoring the foraging behaviour of pinnipeds

The use of stomach temperature data loggers to record prey ingestion has proven to be very valuable when combined with time-depth recorders and satellite tracking devices in studies of seabird foraging ecology. This paper presents a similar system that will allow biologists to determine the precise timing and location of foraging by pinnipeds. The system includes a stomach temperature transmitter and an animal-mounted instrument package. The instrument package contains a satellite transmitter, for remote tracking of movements, and a data logger, for recording dive depth, swim speed, water temperature, and stomach temperature (made possible by an incorporated telemetry receiver). The instrument package can be remotely released upon command to allow data recovery without animal recapture. The system was tested on 6 Steller sea lions Eumetopias jubatus in Southeast Alaska and found to be a powerful tool for quantifying foraging behaviour, although some suggestions for improve ment are presented.