New evidence from unmanned underwater cameras has proved that dolphins are only pretending to be friendly to humans and that the moment that our backs are turned, a sour and indignant expression returns to their faces.

The discovery, which will traumatise animal lovers the world over, was made when Californian marine biologist Mike Varney sensed that the smiling, chattering manner of dolphins and porpoises was somehow a little insincere. He set up a series of remote controlled underwater cameras to record ceteceans interacting with swimmers and divers and then filmed the same dolphins as they left their human companions.

‘It’s fascinating,’ said Varney. ‘As the excited eco-tourists climb onto the boat, still thrilled at their real-life encounter with wild bottlenose dolphins, you can see the dolphins turn away and their cheerful expression suddenly changes. They looked really pissed off, and were sort of tutting and looking skywards. It’s like they were saying ‘I AM SO BORED OF THIS!’

Varney’s research has also demonstrated that their high-pitched animated chattering is also contrived and phoney. Amongst themselves, dolphins manage little more than an occasional indignant grunt, and often can’t even bothered to reply to other family members.

This is the second major discovery by maverick naturalist Varney. Last year his remote controlled cameras discovered that gorillas are actually really smiley when they are left to themselves.