Mixed-species associations between Pantropical spotted dolphins (<I>Stenella attenuata</I>) and Hawaiian spinner dolphins (<I>Stenella longirostris</I>) off Oahu, Hawaii

Abstract

Mixed-species interactions were observed between Pantropical spotted dolphins, Stenella attenuata, and spinner dolphins, Stenella longirostris ,i n Hawaiian waters between 1996 and 1998. Yearround observations were made of spinner dolphins entering a shallow bay off the Waianae (western) coast of Oahu. Mixed-species observations occurred on 19 days between 1996–1998. Spinner dolphins were typically present in greater numbers than spotted dolphins with ratios as high as 75:1. Interspecific behaviours observed include aggression, copulation, and travelling. Five aggressive interactions are described in detail. These behavioural observations are similar to those observed between other delphinid species around the world and suggest that sympatric delphinid species may be more common than previously reported and may have common communication and social signals.