Photo – Bottlenose dolphin attack on porpoise in Cardigan Bay, West Wales – L. Higby
An extraordinary attack on a harbour porpoise by a group of around eight bottlenose dolphins acting in ‘tight formation’ has been witnessed by a marine wildlife expert off Covesea Skerries near Lossiemouth on the south coast of the Moray Firth.
While attacks on porpoise by bottlenose dolphins are not unusual, North Grampian Regional Co-ordinator for the Sea Watch Foundation, Alan Airey, says he has never before seen such an organised attack by a ‘tight pack’ of dolphins.
The attack happened while he was watching around eight bottlenose dolphins, and a mother and calf, leaping, feeding and surfing on the west side of the skerries on Friday 24 May, just as the Bank Holiday began. While the mother and calf remained feeding, slowly the behaviour of the other dolphins changed.
“I also saw a porpoise quite close in heading east. Slowly the dolphins moved further west. Then at about 4.15pm, the eight dolphins started charging about shoulder to shoulder, and I realised they were attacking at least one porpoise. I saw a porpoise had been tossed in the air, with the pack all diving in after it.
“Then I saw a porpoise swimming for its life right in front of the dolphin ‘pack’, the dolphins would surge forward as one as if trying to drown it by forcibly pushing it under, and then I saw another chase which resulted in a porpoise being tossed in the air again.
“It was hard to judge whether it was just one porpoise that was been ‘played’ with, or more than one porpoise. I’ve seen bottlenose attacks on porpoise before but not quite like this with such a tight ‘pack’ of dolphins.”
Alan witnessed the attack through binoculars and says it took place about 800 metres from the coast. Later that day a group of more than 50 bottlenose dolphins were reported at Burghead and later the same evening a minke whale was seen in the area. There have been a couple of dead porpoises found at Covesea and Burghead over the last week, although whether they too were victim to bottlenose attacks is not yet known.
Danielle Gibas, Sea Watch Sightings Officer said:
“We cannot be sure why bottlenose dolphins attack harbour porpoise. There have been several hypotheses ranging from misdirected infanticide to pure aggression by males, but it may well be simply when the two species interfere with one another for space or food. In any event, this was an extraordinary and graphic account of bottlenose dolphin behaviour, which has rarely been witnessed at firsthand.”
Interestingly, exactly the same technique for killing a porpoise was witnessed by Sea Watch director, Peter Evans, off Anglesey a few years ago when a pack of three dolphins pursuing the porpoise, tossing it into the air repeatedly, then jumping on the animal, in that instance crushing its vertebrae and puncturing the lungs.