Intelligent and inquisitive, chimpanzees have always been able to communicate with man.
But this heartbreaking video shows just how desperate this chimp is to be understood and to be let out of his cage.
The chimp is seen in the video motioning to a watching visitor to unlock the bolt on what appears to be a glass door and lift the window, so he can be free.
Tapping on the window the chimp repeatedly urges people standing on the other side of the glass to let them outside.
It links its fingers together, a signal similar to the American Sign Language representation of the word ‘gate’.