When deep in thought...

... some humans stick their tongue out. It looked like this thoughtful-looking grey squirrel was using a similar strategy to solve the problem of raiding a bird feeder at Harlow Carr Gardens this morning.

Interestingly, in today's news, the problem-solving skills of grey squirrels were being compared to red squirrels. 

Of course, birds tend to have a different solution to the problem (see today's extra).