Abstract: Atlantic spotted dolphins (Stenella frontalis) and bottlenose dolphins (Tursiops truncatus) inhabit the western edge of Great Bahama Bank (GBB), Bahamas. In 1998, a photo-identification and behaviour project was initiated in this area. Over three consecutive winters (64 days) dolphins were observed on GBB. Interspecific behaviours are described over 6 years (1998 & 2003). Habitat of GBB is comparable to an adjacent study site on Little Bahama Bank (LBB) that has been under observation since 1985. To date, no photoidentification overlap has been documented between the two study sites (62 identified spotted dolphins on GBB and 220 identified spotted dolphins on LBB). Size of single species groups (GBB=9.1±SD 6.8/LBB=9.3±SD 8.0) and average duration of encounters (GBB=28 min/LBB=31 min) were similar. Mothers with calves on GBB were mottled in coloration, similar to first parturition coloration reported for LBB spotted dolphins. The majority of behavioural activities documented for LBB spotted dolphins during summer months were observed on GBB during winter months, including foraging in the sand, travelling, resting, playing, disciplining, courtship/mating, and intra and interspecific aggression with bottlenose dolphins. In addition, in 2002 male spotted dolphins were observed in dominant mounting behaviour of male bottlenose dolphins (reverse roles to LBB). In the winter of 2003, a hybrid male calf was repeatedly observed with a lactating adult female spotted dolphin. The offshore form of the bottlenose dolphin was observed on GBB, engaging in aggressive activity with resident spotted dolphins. Ongoing research in these adjacent study sites includes genetic sampling and habitat analysis to provide insight into the comparative natures of these two adjacent sandbanks and delphinid species.
Key Words: ATLANTIC SPOTTED DOLPHIN; BOTTLENOSE DOLPHIN; INTERSPECIES INTERACTION; HYBRID; TURSIOPS STENELLA FRONTALIS
Document Type: Research article