The reason the turtle is grinning eerily may be because it is engaging in a behavior called "respiratory coughing." When turtles feel stressed or irritated, they retract their heads into their shells and inhale and exhale quickly to relieve stress on their bodies.
This respiratory coughing behavior is usually accompanied by a special sound that sounds like a turtle laughing. In addition, turtles also make sounds similar to laughter when they are engaged in mating behavior or when they are excited. In general, turtles laugh not because they feel happy or happy, but rather as a physiological response or social behavior.
