Bottlenose dolphins have adapted to a wide variety of habitats around the world. We have had the good fortune to be able to study them where they exhibit two extremes of their ranging patterns, from the multi-decadal residents who spend their entire lives in and around the small enclosed bay system near Sarasota, Florida, to those who range widely through the Sargasso Sea, the only sea in the world that is defined by water currents rather than land boundaries. Our initial tagging studies with satellite-linked transmitters in 2003 and 2005 demonstrated that bottlenose dolphins tagged near Bermuda used the deep waters around the Bermuda Pedestal and nearby banks and seamounts.
On August 30th and 31st, 2016, with support from the Office of Naval Research and Dolphin Quest, we deployed satellite-linked time and depth recording tags on three males and one female off the north side of Bermuda, for studies of lung function and diving (see Fahlman, p. 14 and Moore, p. 15), and ranging patterns. Over the first two months of tracking, the three males (Devonshire, Hamilton, and Pembroke) have remained near Bermuda and nearby banks. After several weeks the female, Paget, went north more than 800 km to a ridge of seamounts. After moving among the seamounts, she moved south, passed east, south, and west of Bermuda, while remaining more than 100 km offshore, and as of November 2nd she is once again approaching the northern seamount ridge (see map).
Defining a population unit for the Bermuda dolphins is challenging, when both localized and long-distance ranging patterns must be considered. More tagging and tracking should help to identify the animals’ ranging patterns. In addition, we have provided small skin samples to NOAA scientists for analyses to compare the genetics of the Bermuda dolphins to those of dolphins elsewhere in the North Atlantic.
This article appeared on page 23 of the 2017 SDRP Annual Report, Nicks n Notches.