Now it turns out that grey squirrels are even more devious than anyone realised.

To protect their winter food stocks from potential thieves, they put on an elaborate show of burying non-existent nuts and seeds, a study has shown.

Scientists say the fake burials are designed to confuse any rival squirrels, birds or humans who might be watching.

The level of deception has astonished animal experts who say it shows a rare form of animal cunning and intelligence.

He found that a fifth of all so-called food burials are fake - and the proportion goes up if they think they are being watched.

"To our knowledge, this is the first study to show evidence of behavioural deception by a rodent, and the first to use an experimental approach to studying deceptive behaviour in in the wild," he says.

The squirrels go to elaborate lengths to keep up the pretence of hiding food.