Three-dimensional dive profiles of free-ranging Weddell seals

Abstract

We used an acoustic tracking system to record under-ice movements of two free-ranging adult male Weddell seals. The two males were unconstrained and interacting with other Weddell seals at a breeding colony in McMurdo Sound, Antarctica. We reconstructed three-dimensional paths of 279 dives by these seals. All dives were less than 20-min duration and none were deeper than 220 m. These three-dimensional dive profiles were compared with conventional time-depth dive profiles recorded using microprocessor loggers. We assigned each of the 279 dives to 1 of 6 classes using an existing classification scheme on the basis of the time-depth trace. Within these, two-dimensionally derived, classes the actual three-dimensional dive profiles at times varied profoundly. Additional parameters obtained with the acoustic system, such as bearing and distance travelled between diving and surfacing points, demonstrate that significant, additional, biologically important information can be derived from the three-dimensional data.