Whilst onboard a wildlife tour boat in Cardigan Bay, two bottlenose dolphins were spotted attacking a harbour porpoise at Ynys-Lochtyn. Bottlenose dolphin kills are the most common cause of death of harbour porpoises in Cardigan Bay. Despite this it is very rare to see an attack. Sea Watch volunteer Louisa Higby who was onboard Ermol V collecting data at the time, took photos of the event. She described seeing lots of splashing about 500 metres from the boat. The porpoise started to swim towards the boat presumably for shelter whilst being chased by two dolphins. One of the dolphins then started to continuously throw the porpoise into the air. At the end of the attack the dolphins were seen nudging the dead porpoise.
It is not clear why dolphins regularly kill porpoises. It is thought that is may be due to competition for the same food source.