Remotely releasable instruments for monitoring the foraging behaviour of pinnipeds

The use of stomach temperature data loggers to record prey ingestion has pr oven to be very valuable when combined with time-depth recorders and satell ite tracking devices in studies of seabird foraging ecology. This paper pre sents 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 inst rument package contains a satellite transmitter, for remote tracking of mov ements, and a data logger, for recording dive depth, swim speed, water temp erature, and stomach temperature (made possible by an incorporated telemetr y receiver). The instrument package can be remotely released upon command t o 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.