Horses use 17 discrete facial movements in communication, compared to 27 for people, 16 for dogs, and 13 for chimpanzees.
I am still rather skeptical as to how such movements qualify as being “communication”. Most people I speak to aren’t even aware of most of these muscular fluctuations, so when I ask them what they meant, they can’t usually say. If there was no intent, then there was arguably no message. Sure, every movement is some indicator of the state of an organism. But the insistence on framing this as being a “language” which can be parsed to have specific reproducible meanings strikes me as obviously and deeply suspect.
By analogy, I can perform a spectrographic analysis of a star and learn a tremendous amount of vital information about it. But I cannot reasonably infer from this that it has a language, and is trying to communicate messages to me. There is no intentionality, nor semantic layer of meanings or concepts.