Offshore bottlenose dolphins (Tursiops truncatus):: Movement and dive behavior near the Bermuda Pedestal

The behavior of offshore bottlenose dolphins (Tursiops truncatus) in deep water and near oceanic islands is not well known. Using satellite-linked, time-depth recorders, we investigated the movements and dive behavior of offshore bottlenose dolphins in the deep waters surrounding the Ben-nuda Pedestal. Three dolphins were tracked from 5 to 45 days and traveled a mean distance of 28.3 km/day where mean water depth was -1,402.0 m +/- 1,120.7 SD. Regular dives during the night (2100-0259 h local time) to depths greater than 450 m (8.9% of total dives), 46.4% of night dives lasting longer than 5 min, and high hematocrit values reveal the deep-diving capabilities of offshore bottlenose dolphins. During the day (0900-1459 h local time), dives tended to be shallow, with 96% of dives within 50 m of the surface, and of short durations, with 52.7% lasting less than I min. At dusk (1500-2059 h local time), the number of dives increased ((X) over bar = 72.4 +/- 19.6), indicating a diet dive cycle. The dive patterns of bottlenose dolphins in Bermuda waters correlate with the reported nightly vertical migrations of mesopelagic prey along the steep-sided Bermuda Pedestal.