Monkey say what monkey wants to do - in sign language

Monkeys at Colchester Zoo have invented their own sign language.

Milly the mandrill covered her face with her hand, a gesture staff feared meant she had bad sight before realising she was saying "leave me alone".

US researcher Mark Laidre said that her action - copied by others in the troop - was the first recorded case of a monkey using sign language for cultural benefit, not for genetic or environmental reasons.

Zoo curator Sarah Forsyth said Milly's signal "could be as simple as 'I can't see them so they can't see me'". Staff are teaching the mandrills - from central African rain forests - more sign language.