Keepers at London Zoo are trying to train their Bolivian squirrel monkeys out of their habit of stealing visitors' sunglasses.
The zoo's gang of 18 Bolivian squirrel monkeys have stolen seven sunglasses off the heads of visitors in recent weeks, reports the BBC.
Keeper Kate Saunders, 28, said: "They love to see their reflection in the lenses... the young ones, they are the cheekiest. They love the glasses the most.
"They are attracted to the shiny lenses on the sunglasses. Once they get hold of a pair they all race round the enclosure chasing the monkey with the glasses."
The zoo plans to wean the monkeys off thieving by giving them sunglasses with bitter apple sprayed on them as a deterrent.
Four years ago the thieving monkeys underwent another rehabilitation programme after stealing mobile phones.
It is now hoped that the shades will taste so unpleasant that visitors' sunglasses will no longer be a target for the monkeys.