Do animals use sign language?

Animal behaviour expert Eleanor Drinkwater took on this question...

This is a really great question. And there is at least one example of two non-human species communicating via sign language. So this particular case comes from a chimpanzee called Washoe who was trained by researchers to be able to communicate via sign language. What the researchers then found was that when the chimpanzee had her own baby, she then proceeded to teach the baby how to also communicate via sign language, which is a really lovely example of how animals can teach their babies how to communicate.

As for the second question about whether there's been two different species which have been seen communicating via sign language.

Other than humans communicating with different types of primate, I don't know of any examples of when this has happened.

What is, however, so much more impressive than two animals communicating via a shared language, is the amazing diversity in nature that we see of different ways in which animals can communicate despite having no shared language. So a really lovely classic example of this is honeyguides.

So these are amazing little birds, which have been known to show humans and other animals where to find sources of wild honey, despite not sharing their language. But even more impressive than that, in my opinion, one of my favorite examples of this, is the relationship between the red-breasted nuthatch and chickadees.

So chickadees are these incredible birds, who have an immense ability to be able to encode very, very detailed information in their alarm calls. So within one alarm call they can indicate what the type of predator it is, or how big the predator is.

And the really amazing thing is despite the fact that nuthatches and chickadees are not very closely related, nuthatches are able to listen in on these calls and understand in detail, exactly the threats which the chickadees are describing and be able to respond in an appropriate way, which I think is just an incredible, incredible piece of evidence showing how two animals of very different species, can understand each other's calls despite not having a shared language. And the incredible thing is these are just the species that we have studied.

There's probably many other incredible examples of species communicating without a shared language that we just still don't know about.