Chimpanzee 'asks' people to free him at Wales zoo - video
The chimp is seen pointing at a window bolt and making an 'open' gesture to the people looking on.
The ape also connects its fingers together in a way that is similar to the American Sign Language meaning of the word 'gate', reports The Telegraph.
The visitor to the Welsh Mountain Zoo who filmed the video is heard saying: "He wants us to lift the window up."
Peter Dickinson of the zoo has previously written about the use of sign language with animals as part of their enrichment scheme.
> Chimpanzee bottle feeds tiger cubs at Thai zoo: Video
> Ape injures girl following zoo escape