"Dirty Jobs" Monkey Thoughts
That got me thinking about how every animal I can think of has their own special signals with their own special meanings, and they act like every other animal understands it. I started wondering whether some of these things are cultural like they are in humans. We have both universal and local signals, for instance laughing and smiling are both universally understood, but certain gestures are not. For instance, shaking your head means no in some cultures and yes in others. So are there groups of monkeys for whom flapping your arms means something besides aggression, perhaps a warning of danger? I don’t know, and I don’t even know where to start looking to find out. I would speculate that there are, because I know that some primates have some form of culture, such as tool use. But I don’t know.
I also thought about how effective these signals are for interspecies communication. Some of them, like barring the teeth, are probably pretty effective, and seem to be used by most animals as a way of saying, “Don’t mess with me.” But hitting your head with your hands? That seems far less likely to trigger any kind of understanding. Maybe this is almost like sexual selection, where all that matters is what the majority of the species uses, and it’s fairly arbitrary.
I think that there are some things that are fairly universal, base instincts inherited from the ancient mammals, or even further back, while the rest are arbitrary, and only have meaning inside the species. But because of the universal instincts, the animals don’t recognize that these signals will be meaningless past the species boundary. That’s just my guess though, I’m sure some biologist out there actually knows.