London - Fun-loving, friendly and bright as a button, dolphins are often painted as the most gentle of all ocean creatures.

But according to research, not only are dolphins actually “less sophisticated than chickens” - but their playful nature masks a darker, more aggressive side.

Scientists from the sea mammal research unit at St Andrews University say they have spotted bottlenose dolphins engaging in wanton acts of violence.

They found the marine mammals will often try to isolate and then kill smaller harbour porpoises, without any intention of eating their carcasses.

The leader of one particularly vicious pod was even dubbed Jack the Flipper thanks to his violent tendencies.

And a six-year Australian research project found that gangs of males try to assert their authority by forcefully mounting other males - often resulting in bloody fights.

The findings sit uneasily with a growing campaign led by experts who claim that the mammals deserve the same rights as humans because of their apparent high level of moral sophistication.

Last year scientists made a bid to have dolphins reclassified as “non-human persons”, and said killing them should be treated as murder. But zoologist Justin Gregg, who works for the US Dolphin Communication Project, believes we have allowed sentimental ideas about the species to cloud our judgment.

“Dolphins are fascinating in their own right, but in terms of intelligence they are nowhere near as special as they have been portrayed,” he said.

“Dolphins do have a unique signature whistle, and it’s possible that they could use this in order to communicate.

“But they do not seem to have alarm calls or food calls - so in that respect they are less sophisticated than chickens.”

He added: “If we could just stop looking at them through the lens of our human condition, then we might open our minds to the idea that many other species have equally wondrous lives.” - Daily Mail