Residents at the Bristol Zoo can get a little touchy about their privacy.
One local man found that out the hard way when he visited the attraction and began snapping photos of a gorilla minding its own business.
Bob Pitchford, 67, was on a visit to the city's zoo last week when he spotted the large ape chewing on some grass.
He took his camera out to take a photo but when the the mammal caught sight of Mr Pritchard he swiftly made the rude gesture.
The gorilla obviously didn't take too kindly to the interruption in its regular grass chewing time and showed his displeasure apparently in the only way it knew how — by flicking the photographer off.
The unnamed flipper of the bird must not have made his point too clear, however, because Pitchford said he didn't even realize he had received the offense until he came home and reviewed the pictures.
'When I saw the pictures, I just thought "you little devil",' he added. 'He really does look a bit cheese off.
'I quite regularly photograph the animals at Bristol, but I've never seen anything like this.
'Gorillas are really good at expressing their feelings. I was just really lucky to capture this.'
This isn't the first documented time we've seen such fierce expression from apes, who also can be well versed in physical communication.
Is this a terrifying image of things to come?
Rise of the Finger of the Apes