I always thought it was due to clearing the lungs out or to regulate them but then I saw a turtle yawn under water. I then thought it’s ancestors wouldn’t have been swimmers so maybe it’s instinctive still, but then it would need a mechanism to prevent water inhalation. So why retain the yawn.
Perhaps as you say it’s more about visual communication to others around you.
I always thought it was due to clearing the lungs out or to regulate them but then I saw a turtle yawn under water. I then thought it’s ancestors wouldn’t have been swimmers so maybe it’s instinctive still, but then it would need a mechanism to prevent water inhalation. So why retain the yawn.
Perhaps as you say it’s more about visual communication to others around you.