Three-dimensional dive profiles of free-ranging Weddell seals

We used an acoustic tracking system to record under-ice movements of two fr ee-ranging adult male Weddell seals. The two males were unconstrained and i nteracting 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 2 20 m. These three-dimensional dive profiles were compared with conventional time-depth dive profiles recorded using microprocessor loggers. We assigne d 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-dimensionall y derived, classes the actual three-dimensional dive profiles at times vari ed profoundly. Additional parameters obtained with the acoustic system, suc h as bearing and distance travelled between diving and surfacing points, de monstrate that significant, additional, biologically important information can be derived from the three-dimensional data.