Postmortem evidence of interactions of bottlenose dolphins (Tursiops truncatus) with other dolphin species in south-west England.

Reports of violent interactions between bottlenose dolphins (Tursiops truncatus) and harbour porpoises (Phocoena phocoena) in the coastal waters of the UK are well documented. Examination of stranded cetaceans by the Cornwall Wildlife Trust Marine Strandings Network and the UK Cetacean Strandings Investigation Programme has indicated that seven animals, of four other species, found stranded in south-west England, had pathology consistent with bottlenose dolphin interaction, including two juvenile and two adult common dolphins (Delphinus delphis), one juvenile pilot whale (Globicephala melas), one juvenile Risso's dolphin (Grampus griseus) and one adult striped dolphin (Stenella coeruleoalba). Although recorded traumatic lesions were often not as severe as those found in harbour porpoises, it is probable that the interactions did contribute to stranding and/or death in all four of the juvenile animals examined. Furthermore, analysis of photographs taken before establishment of the Marine Strandings Network revealed rake (teeth) marks consistent with bottlenose dolphin interaction on one stranded common dolphin in 1992. A number of causes have been suggested for these interactions in harbour porpoises stranded in the UK and it is possible that any combination of these factors may also be implicated in the cases described in this report.