Looking away when yawning
Like hippos, bears and wolves will often yawn and display their teeth as a sign of aggression before an attack. According to a study in International Wildlife Magazine, baboons will also yawn in a threatening manner to establish pecking order in groups.
When animals that live in groups, like lions, don't want a yawn to be perceived in a threatening way, they'll often look away and avoid direct eye contact when they do it. Others learn to cover their teeth with their lips. In this way, members of their groups won't look at yawns as aggressive moves.