Top - Malayan Forest Gecko (Cyrtodactylus pulchellus) 

Center/Bottom - Crested Gecko (Correlophus ciliatus)

Why do geckos (and some other terrestrial lizards) lick their eyeballs?

Wouldn’t you, if you could? I sure would. Other than the fact that they have cool long tongues, geckos (and many of their terrestrial brethren) have non-functional eyelids, but rely strongly on their eyesight. In order to maintain their vision, they lick their eyes!

Several mammals, such as okapi and giraffe, also lick their eyes, though they still have functional eyelids.

Unrelated cool fact! "Eyelash geckos", otherwise known as crested geckos, were once thought to be extinct! In 1994, however, they were re-discovered in a southern province of New Caledonia. They bred easily in captivity, and are now one of the most popular pet reptiles.

Malayan Forest Gecko via Wikimedia Commons

"Lizard Lick" via It’s Erin! on Flickr