They leap through hoops, communicate with clicks and are seen as among the most intelligent of animals.
But Northern Ireland’s first confirmed case of a killer dolphin casts a whole new light on what are usually regarded as peace-loving mammals.
Scientists who carried out a post-mortem examination on the corpse of a porpoise found on rocks on the Co Antrim coast early in the New Year have revealed that its death is consistent with a bottlenose dolphin attack.
It’s the first such killing documented here, although similar incidents have been reported in California, Wales, off the Cork coast and in the Moray Firth in Scotland.
It seems that the porpoise may have been mistaken for a bottlenose calf — infanticide has been recorded among some bottlenose colonies in the British Isles, according to Irish Whale and Dolphin Group member Ian Enlander.
Ian believes he saw the culprits — two bottlenose dolphins — when he was walking along the seafront at Whitehead on January 13.
Later that day, Ian received a report of a ‘stranded dolphin’ near Whitehead and the next day kayaker Bob Nixon found a dead harbour porpoise towards Blackhead. “The corpse of a 1.45m long male was on the rocks, looking rather forlorn with no obvious sign of injury and in very good condition, so much so that I did check for any signs of life — but this was one very dead harbour porpoise,” Ian said.
Staff from Northern Ireland Environment Agency collected the remains for examination by pathologist Tony Patterson, who made a startling discovery. “The porpoise was recorded as having, amongst other injuries, multiple rib fractures and the blubber separated from the underlying muscle mass — all consistent with a massive impact,” Ian said.
“The veterinarian’s conclusion was that the pattern of injuries was consistent with a bottlenose dolphin attack. So in the space of 24 hours I had seen my very first murder victim and indeed probable murderer.”
Researchers in the Moray Firth have been documenting similar behaviour for more than 10 years, Ian said.
One observer has described seeing the dolphins “flipping up a porpoise with their beaks and battering it when it landed on its back on the water”.
“Adult bottlenose dolphin are substantial in size, weighing over four times more than harbour porpoise and capable of tremendous bursts of speed and hence of delivering a substantial impact,” Ian said.
“Quite why this aggressive interaction with porpoise occurs is unclear. Suggestions include competition for food, territorial conflict or sexual frustration. A study of bottlenose dolphin calf corpses in north-east Scotland has shown that many of these also show evidence of being attacked and killed by adults of the same species — yes, some bottlenose dolphin populations practise infanticide.
“This has led to a suggestion that, given the similarity in size between these calves and harbour porpoise, the adult dolphins are actually attacking the porpoise mistaking them for bottlenose calves.”
Ian had some words of reassurance for anyone who is afraid the bottlenose dolphin could be the new Jaws: “There is no record of bottlenose dolphins deliberately attacking people.”
Other animals on the attack
It’s been suggested that orca attacks — as documented on David Attenborough’s BBC series ‘The Trials of Life’ — may be driving down seal populations on the northern coasts of Scotland.
A seagull dive bombed Belfast Zoo’s penguin enclosure at feeding time in August 2008, snatching a fish from the beak of an unfortunate penguin, as recorded by a visitor who posted the video on YouTube.
The ‘Battle of Kruger’ video shows a pride of lions seize a baby cape buffalo at an African watering hole, only for the infant to stagger back into the water and be grabbed by a crocodile. It struggled free, back to the lions, but was carried to safety when buffalo attacked the lions.