Geckos are known for their distinctive eyes. A common question is whether they close them. The answer varies by species, as their ocular structures show diverse adaptations for vision and eye protection.
The Eyelid Question
Most gecko species do not possess movable eyelids like humans or many other lizards. Instead, their eyes are covered by a transparent, fixed membrane called a “spectacle” or “brille.” This specialized scale acts like a permanent, clear contact lens, continuously protecting the eye from dust, debris, and physical damage. Due to this fused structure, these geckos cannot blink or close their eyes. This adaptation provides constant protection without interrupting their vision, benefiting nocturnal species in low light.
How Geckos Manage Without Eyelids
Since most geckos lack movable eyelids, they use a unique method to keep their eyes clean and moist. They regularly lick the spectacle covering their eyes with their tongues. This behavior removes accumulated dirt, dust, or debris from the transparent membrane. Licking also hydrates the eye, ensuring the spectacle remains moist and clear for optimal vision. This tongue-wiping action functions similarly to blinking, maintaining ocular hygiene and clarity.
Geckos That Do Close Their Eyes
While most geckos lack movable eyelids, the Eublepharidae family, known as “eyelid geckos,” possesses functional, movable eyelids. This family includes species like the Leopard Gecko (Eublepharis macularius) and the African Fat-tailed Gecko (Hemitheconyx caudicinctus). Unlike their lidless counterparts, these geckos can blink, close their eyes completely, and wipe away debris, much like other lizards. This trait allows them to protect their eyes from environmental factors.
Sleeping With Open Eyes
For gecko species without eyelids, sleeping involves keeping their eyes open. Despite appearances, these geckos do enter a sleep state. To manage light exposure, they can significantly constrict their pupils, sometimes reducing them to tiny vertical slits. This pupil constriction helps limit the amount of light entering their eyes during rest.
Many lidless geckos also seek dark, secluded spots for sleeping, such as under leaves, bark, or rocks, to minimize light. While their eyes remain open, their brain activity shifts to a resting state, demonstrating that sleep is not dependent on physically closing their eyes. Eyelid geckos, however, such as Leopard Geckos, can fully close their eyes for sleep, offering complete protection and darkness.