Communication among chacma baboons is mostly non-verbal. It may can take various forms : postures, ways of straightening the tail, screams and yelps. Eye blinks, ear movements or expressive grimaces ... mimicry is numerous and can mean fear, threat, submission or benevolence. But we must not rely on what we see to interpret the grimaces of baboons, nor compare them to human expressions. For example, a baboon opening its mouth wide and revealing its huge canines may actually only express a sense of peace, while the numerous grimaces of intimidation strangely look like smiles.