Harbour porpoises were found dead on the north-east coast of Scotland. The cause of death showed that bottlenose dolphins must have attacked them, but the reason is unknown. Data that were collected from direct observation showed communication between adult bottlenose dolphins and calfs provided proof that infanticide was most likely present in this population. Possible reasons for the incident was most likely caused by competition for prey, sexual frustration, play fighting, or feeding interference. The size range between harbour porpoises and bottlenose dolphin calves are very similar. The signs of attack by the bottlenose dolphin could be caused by previous interactions, therefore having infanticidal behavior. These two species also inhabit
