Do lizards lick their own eyes?

Lizards are a diverse group of reptiles that are found worldwide in a variety of habitats. They have several adaptations that aid their survival, including the ability to detach their tails if attacked by a predator and the ability to regenerate lost limbs or tails over time. One interesting behavior that some lizard species exhibit is the apparent licking or cleaning of their own eyes with their tongues. This has led to the common question – do lizards actually lick their own eyes?

The short answer is yes, some lizard species do regularly lick their own eyeballs. This is done through a process called lenitive contaction. There are several reasons lizards engage in this eye-licking behavior. First, it is a way for them to clean and lubricate their eyes to prevent dust and debris buildup. The tongue helps distribute tears across the surface of the eyeball to keep it moist. Second, lizards lack eyelids and cannot blink like humans, so licking their eyes is a way to provide occasional moisture and lubrication to prevent the eyes from drying out. Third, licking may help remove old skin cells and debris that can accumulate on the surface of the eye.

So in summary:

– Do lizards lick their own eyes? Yes, some species exhibit this behavior.

– Why do they lick their eyes? To clean them, lubricate them, and prevent buildup of debris.

– How are they able to lick their own eyes? Through a process called lenitive contraction of specialized muscles around the eyeball.

Now let’s dive deeper into the details and science behind this unusual lizard behavior.

Anatomy of the Lizard Eye

To understand why lizards lick their eyes, it helps to first understand the anatomy and function of the lizard eyeball.

Lizard eyes share some general similarities with human eyes, but also have some key differences:

– The eyeball itself is globe-shaped, with a tough outer layer called the sclera.

– Inside is the choroid, which contains blood vessels and supplies the eye with blood.

– The iris and pupil work together to control light levels entering the eye, just like in humans.

– The lens focuses light onto the retina at the back of the eye.

– The retina contains photoreceptor cells called rods and cones that detect light and send signals to the brain.

However, lizard eyes also have some distinct properties:

– Lizards lack a conjunctiva layer that lines the inside of the eyelids and covers the white part of human eyes.

– They also lack a lacrimal apparatus to produce tears. Their eyes are lubricated primarily by the nictitating membrane.

– Importantly, lizards cannot move their eyes within the eye sockets. Their eyes are essentially fixed in place.

– Lizards also lack eyelids and cannot voluntarily blink like humans. A transparent scale called the spectacle covers and protects the eye.

So without eyelids, blinking, or tear production, lizard eyes would be prone to dryness, debris buildup, and damage without a way to lubricate and clean themselves. This helps explain why licking behavior evolved.

The Nictitating Membrane

Lizards have a structure called the nictitating membrane that plays an important role in eye lubrication and cleaning.

The nictitating membrane is a transparent or translucent third eyelid that can move horizontally across the eye to moisten and protect it. It spreads fluid like mucus and lymph across the eyeball surface.

However, the nictitating membrane cannot fully cover the eye or move downward to remove debris. This is why lizards also lick their eyes – to supplement the functions of the nictitating membrane.

The tongue helps distribute moisture and fluids evenly across the exposed parts of the eyeball and removes particles or skin accumulation that the nictitating membrane cannot reach.

Lenitive Contraction Allows Eye Licking

For lizards to be able to lick their own eyes, they need specialized muscles and nerve connections that allow this type of contraction and movement.

Lizards have evolved a mechanism called lenitive contraction that enables the eyeball to be compressed within the eye socket and pushed forward out of the mouth’s reach.

It involves synergistic contraction of six extraocular muscles that control eye movement:

– The lateral rectus muscle
– The superior rectus muscle
– The inferior rectus muscle
– The superior oblique muscle
– The inferior oblique muscle
– The retractor bulbi muscle

Through specific activation and contraction of these muscles, the eyeball can be pushed forward and downward out of the mouth’s reach.

Nerves that serve these extraocular muscles connect to the trigeminal nerve in the brain, which controls musculature and sensation in the face and mouth region.

This trigeminal nerve activation allows for precision movement of the eyeball by the mouth, tongue, and jaw needed for licking.

Evolution of Lenitive Contraction

Lenitive contraction is not found in all lizards but is most highly developed in geckos, iguanas, monitor lizards, and other species that exhibit frequent eye-licking.

This ability likely evolved through natural selection. Lizards born with slight anatomical variations that allowed tongue-to-eye contact may have had improved eye cleaning ability and eye health.

This would confer survival advantages, allowing those traits to be passed down and specialized through generations via the lens of evolution.

Over time, the intricate nerve connections between the trigeminal nerve and extraocular muscles evolved to enable the precise control needed for lenitive contraction and eye licking.

Functions and Benefits of Eye Licking in Lizards

As mentioned briefly earlier, lizards lick their eyes for a few key reasons and benefits:

Cleaning and Debris Removal

The tongue helps remove dust, dirt, skin cells, and other debris that accumulate on the exposed eyeball surface that cannot be reached by the nictitating membrane alone.

The mechanically scrubbing action of the tongue likely removes potentially irritating or obscuring material.


Without tear glands, lizard eyes depend on the tongue to spread moisture and oily secretions across the eyeball for lubrication and to prevent drying out.

The mucus in saliva may also contain antibacterial properties to protect eye health.

Distribution of Protective Fluids

As mentioned, the nictitating membrane secretes protective fluids across the eye. The tongue likely helps evenly spread these secretions to fully coat the eyeball.

Prevention of Damage

By keeping the eye surface clean, moist, and lubricated, regular licking can prevent damage from debris buildup and dryness over time.

Licking may also help remove pathogens or parasites before they can infect or irritate the eyeball surface.

Differences Between Lizards Species in Eye Licking

While many lizards exhibit eye licking using lenitive contraction, there are some differences between species:


Geckos lick their eyes very frequently, sometimes every several minutes. Other species like iguanas may only lick occasionally. Some reptiles don’t seem to exhibit eye licking at all.


Smaller geckos often lick just one eye at a time, rapidly flicking the tongue across the eyeball surface. Larger lizards like monitors may open their mouths widely to lick both eyes simultaneously.


Lizards evolved differences in the trigeminal nerve branches and extraocular muscles that likely correspond to differences in licking frequency and technique. More research is needed.

Certain families like chameleons have eyes that can move more independently, reducing the need for lenitive contraction.

Overall, smaller diurnal lizards seem to gain the most frequent benefits from dedicated eye licking adaptations. Further comparisons between species may reveal interesting evolutionary patterns.

Remaining Questions and Future Research

While we now have a decent understanding of how, why, and which lizards lick their eyes, some questions remain that could be addressed by future research:

Detailed Anatomical Studies

While the general muscle and nerve anatomy that allows lenitive contraction is understood, detailed dissections could reveal subtle differences between species that correspond to eye licking abilities.

Sensory Activation Mechanisms

What sensory cues initiate eye licking behavior? Is it triggered by sensations of dryness on the eyeball surface? Do lizards have a natural rhythm or “biological clock” controlling the behavior?

Antibacterial Properties

Do chemical properties of lizard saliva confer antibacterial benefits when spread over the eyeball? Or is lubrication the primary function?

Function in Nocturnal Lizards

Some nocturnal geckos also exhibit frequent eye licking. What benefit does this provide during the night? Are their eyes more prone to debris buildup for some reason?

Further research and observations into these and other questions will reveal more about the curious phenomenon of eye-licking across different lizard species.


In conclusion, many lizard species do indeed lick their own eyes using a process called lenitive contraction. This involves specialized musculature around the eyeball that allows it to be pushed forward and exposed for the tongue to reach.

Lizards likely evolved this mechanism through natural selection because it provides several benefits for eye health and function. Eye licking helps clean debris, evenly spread moisture and protective fluids, prevent desiccation, and avoid damage that could occur without eyelids and blinking.

Different lizard species exhibit variations in eye licking frequency and technique based on their anatomy and habitat. While we now understand the general mechanisms behind this unusual lizard behavior, further research can provide deeper insight into the detailed anatomical adaptations and triggers involved.

Lizard Family Frequency of Eye Licking Licking Technique
Geckos Very frequent Often one eye at a time
Iguanas Occasional Tongue spread over both eyes
Chameleons Rare Eyes can move more independently
Monitors Moderately frequent Open mouth wide to lick both eyes

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