Abstract

Although release of captive cetaceans for reestablishment of extirpated populations has not yet been necessary, current releases of excess animals could provide information for future reintroduction efforts. Previously successful reintroductions have been correlated with large numbers of individuals released with a high probability of mortality . The purpose of this study was to determine factors that would increase probability of survival for small numbers of releasees. I examine ethical issues pertaining to the arguments that a minimal set of duties owed to captive individuals extends to those being released. In this release, efforts to meet such duties included pre-release determination of associations and ability to forage, assessment of local dolphin behavioral ecology to best time the release and development of trained response to research vessels with remote tracking to monitor and recapture individuals unable to adapt. ;The group comprised 6 wild-born adults and 3 captive-born juvenile females. Male association patterns were recorded using focal animal and instantaneous sampling of activity state and proximity. Boat surveys of the coastal dolphin population were conducted for 27 months . Releases were tracked via radio telemetry, boat surveys and reported sightings. ;Pre-release association patterns changed during an episode of agonistic interactions and did not persist post-release. Three cases of stress-related illness associated with the shift in associations were monitored. Although soft release was timed to coincide with peak dolphin abundance, releasees did not join wild groups. Resighting frequencies of wild dolphins suggest an open population where individuals have few close associates and extensive ranges, thus it is not surprising that 5 released animals were not sighted beyond 2-4 weeks of monitoring. The only known mortality was a newborn calf. An adult male, the mother of the newborn calf, and a juvenile female were recaptured due to visible weight loss and interaction with humans. ;Recommendations include use of both radio and satellite tracking to maximize chances of relocating releasees and more emphasis on foraging ability pre-release. Additionally, further examination of mechanisms to enhance group cohesion and means of provisioning may enhance chances of survival and integration into wild populations