How do alligators close their ears, nose, and throat to swim underwater?
Alligators also have a “third eyelid” like all crocodilians have a “third eyelid” which is really a transparent membrane properly called a nictitating membrane. While they have the same kind of eyelids as we do: an upper eyelid that closes from the top down, and a lower eyelid that closes from the bottom up, the third eyelid moves to cover the eye from the front to the back automatically when the animal submerges, and acts like the see-through glass of a diver’s mask. While the animal can’t see clearly through the opaque membrane, it can see dark and light and protects the eye itself from damage by sticks and other things while the animal swims under water. While alligators have a leathery flap of skin over the ear openings on the side of the head, which protects them from damage, it doesn’t actually keep out water because the flap is an open slit towards the rear. The actual ear canal is covered over by the tympanum- a tough membrane that acts as the ear drum. This membrane vibrates a
