Country diary: bottlenose dolphin attack shatters Flipper illusions

A bottlenose dolphin lifting a harbour porpoise up in the air at Chanonry Point in the Moray Firth. Photograph: Jamie Muny/PA

There are occasions when nature shatters our cosy assumptions. Last week we were watching the bottlenose dolphins (Tursiops truncatus) on the Moray Firth, much loved by tourists because they come so close to shore. They flip and leap, roll and dive, singly or in pods of a dozen or more, only a few yards from camera-clicking visitors thronging the shingle spit.

The dolphins gather in the Chanonry narrows to feast on salmon migrating upstream to spawn. We often see salmon being flung high in the air and swallowed whole. A feeding spectacle. We know dolphins eat fish and we are comfortable with it. But what we witnessed in front of our lenses that day spun us into shock. Forget film-star Flipper, forget frolicking Fungie in Dingle Bay, forget chummy Sebastian in Disney’s Shark Tale – these Moray Firth dolphins are killers.

‘Dolphins don’t eat porpoises, they just kill them. They ram them, bite them, throw them and catch them, playing with them like a cat plays with a maimed mouse.’ Photograph: Sea Watch Foundation

It wasn’t salmon they were throwing high into the air that balmy afternoon, it was a harbour porpoise (Phocoena phocoena), at less than 2m long half the size of a dolphin and probably a tenth of its body weight). Yes, another cetacean. Another common cetacean that we all enjoy seeing in our coastal waters.

And the dolphins weren’t feeding. Dolphins don’t eat porpoises, they just kill them. They ram them, bite them, throw them and catch them, playing with them like a cat plays with a maimed mouse. We don’t really know why. The scientists in the University of Aberdeen’s Cromarty Lighthouse field station, the leading authority on the bottlenose dolphins, tell me they don’t know either, but it’s not uncommon. Dead porpoises are found washed up, gashed with dolphin-teeth scars and ribs stove in. Is it territorial? Do the dolphins see them as competition for food? Or is it much darker than that – is it fun? Is it a ghastly gang game, killing for sport?

I watched the body language of my friends. It wasn’t what they wanted to believe of these intelligent, semi-human mammals that we have idolised. It was an “Oh my God!” moment – stern, disbelieving faces, shock fizzing and spinning us into silence. Right there, only 30 yards away, right in front of our noses, a gang of beautiful killers having fun.