A Mass-Stranding Event or Rough-Toothed Dolphins (STENO BREDANENSIS) in the Florida Keys (Florida, USA): II. Release and Tracking

There are very few data on the life history and biology of Steno bredanensis. This species is typically thought to inhabit deep tropical and subtropical waters. Contact and observations by humans have been reported on a limited basis. On 2 March 2005, a minimum of 70 roughtoothed dolphins stranded along a 3 km stretch of the Florida Keys. Of the 26 dolphins transported to the Marine Mammal Conservancy (Key Largo, FL) for rehabilitation, 15 expired, 4 are still receiving care, and 7 were successfully rehabilitated and released. Various conditions were required for release and included: measured blood values within predetermined “normal” physiologic ranges, negative results for all infectious and non-infectious diseases, discontinued use of antibiotics for at least 10 days prior to release, and demonstration of behavioral stability and competence. SPOT4 and SPLASH model satellite tags and VHF trackers were mounted on 2 of the individuals to enable post-release monitoring of release success and to acquire information on species migration, distribution, diving capacity, and habitat utilization. On 3 May 2005, 7 dolphins were transported to the release site 14 miles east of Key Largo, Florida and were simultaneously released into waters 150 meters in depth. The satellite and VHF tracking devices indicated that the animals maintained pod structure and were successfully navigating shallow water habitats off of Andros Island in the Bahamas. This supports prior unpublished observations of S. bredanensis in shallow areas and may indicate utilization of benthic food sources. Timedepth recorders in the SPLASH tag indicated dives of up to 300 m depth, which has been previously undocumented for this species. This event was the largest release of cetaceans in documented history, and this study exemplifies the potential for research inherent in rehabilitation and release efforts.