While we're on the topic of animals that act like humans, consider this very sad, very famous case: Nim Chimpsky. Raised to be a human boy, when the funds ran out and Nim got to the age equivalent of a five year old boy, he was sent off to live with other chimps. Imagine that you are a five year old boy and get put into a cage with chimps...

And despite Nim's handlers' published opinion, it seems he did use ASL for communication, as have other chimps more humanely looked after.