Mixed-species associations of striped dolphins (Stenella coeruleoalba), short-beaked common dolphins (Delphinus delphis), and Risso’s dolphins (Grampus griseus) in the Gulf of Corinth (Greece, Mediterranean Sea)

Surveys to assess cetacean presence were conducted in July 1995 and 1997 in the Gulf of Corinth, which is an almost-enclosed sea in Greece, Eastern Mediterranean. The dolphin sighting frequencies were high (0.043 sightings/km). Four dolphin species were encountered: striped dolphins (Stenella coeruleoalba), short-beaked common dolphins (Delphinus delphis), Risso’s dolphins (Grampus griseus) and bottlenose dolphins (Tursiops truncatus). Bottlenose dolphins were encountered only once. Thirteen dolphin sightings were single-species (striped dolphins) and seven were mixed-species with either two species (striped and common dolphins in five sightings), or three species (striped, common, and Risso’s dolphins in two sightings) in the group. In all mixed-species sightings, Risso’s dolphins and common dolphins were always and by far the minority species present. To date, no singlespecies groups of Risso’s or short-beaked common dolphins have been observed in the Gulf of Corinth. Interspecific rake marks on the Risso’s dolphins, and behaviours observed through video analysis, indicate potentially complex and regular interspecific interactions. Our results support the idea that interspecific interactions between sympatric cetacean species in the area are common, and apparently complex.