Can Lizards See In The Dark? A Detailed Look At Lizards’ Vision Capabilities

Lizards are fascinating creatures that have adapted over millions of years to thrive in a variety of environments. Many lizard species are most active during the day, but some have excellent night vision abilities that allow them to hunt and navigate terrain when the sun goes down.

If you’re short on time, here’s a quick answer: Most lizards cannot see well in complete darkness, but some gecko species have advanced eye structures that give them decent night vision capabilities.

The Basic Structure and Function of Lizards’ Eyes

Cones, Rods and Photoreceptive Cells

Lizards have specialized photoreceptive cells called cones and rods in their retinas to detect light, similar to human eyes. Cones allow lizards to see color and fine details, while rods function better in low light.

Some lizards have up to five types of cones, allowing them to perceive ultraviolet, violet, blue, green and red light (American Museum of Natural History).

Additionally, some lizards have a third type of photoreceptive cell that detects changes in light intensity, which aids their vision in varying light conditions. For example, the nocturnal Tokay Gecko possesses this special cell, helping it to hunt at night (Roth and Kelber, Current Biology, 2019).

Limited Color Vision Compared to Humans

While some lizards have good color vision, most see a more limited range than humans. Anoles and iguanas have trichromatic vision from three cone types, perceiving violet, blue and green light. But they cannot distinguish red and green hues apart as sharply as humans (HowStuffWorks).

So while some lizards enjoy enhanced color perception, most lag behind the vivid red-green vision that humans possess.

Differences Between Diurnal and Nocturnal Species

Diurnal (day-active) lizards generally have round pupils and colored oil droplets in their retinas to fine-tune color vision. Nocturnal species usually have vertical slit pupils that open wide to allow more light in dim conditions (AMNH).

Additionally, nocturnal geckos have a reflective layer called the tapetum lucidum behind their retinas. This mirror-like surface bounces light back through the rods, essentially giving the light a second chance to be detected. This helps geckos see well in low light (National Geographic).

So lizards have adapted differences in their vision based on their activity patterns. Diurnal species focus on color, while nocturnal geckos maximize light sensitivity.

Advanced Adaptations That Help Some Lizards See at Night

Enlarged Corneas and Pupils Gather More Light

Certain nocturnal lizard species like geckos have developed oversized corneas and pupils to allow more light to enter the eye. Their vertically slit pupils can open very wide at night, permitting 2-3 times more light than a round pupil the same size.

This adaptation gives their eyes far better light-gathering capacity in darkness. Some geckos also have a spherical lens in their eyes to focus stray light more efficiently. Together, these features maximize their ability to utilize whatever little nighttime illumination exists.

A Reflective Tapetum Enhances Dim Light Sensitivity

Many nocturnal geckos, skinks and eyelid geckos possess a reflective tapetum lucidum layer behind the retina. It acts like a microscopic mirror, reflecting light back through retina for additional photoreceptor stimulation. This literally gives their eyes a second chance to register the image.

It’s why gecko eyes often seem to glow at night – the tapetum is reflecting light directed into them. This built-in “night vision gear” amplifies their ability to perceive shapes, objects and motion in near darkness.

More Rods Than Cones Support Low Light Vision

Lizards active after dusk tend to have retinas densely packed with rod photoreceptors – the type specially adapted for monochromatic night vision. They contain a very light-sensitive pigment called rhodopsin optimized to work at low light intensities.

The gecko retina in particular has one of the highest densities of rod cells documented for any terrestrial vertebrate. In contrast, theircone cells – used for seeing color and detail – are far fewer in number. This distribution favors enhanced sensitivity in low light over color perception.

Working synergistically, specialized retinal rods, enlarged optical structures, and reflective tissue coating all help certain lizards make the most of scarce ambient light at night. These visual system adaptations permit heightened illumination detection – key to an active after-dark lifestyle.

Examples of Lizards with Relatively Good Night Vision

Geckos Have Impressive Low Light Abilities

Geckos are well-known for their remarkable ability to cling to surfaces using specialized toepads containing millions of microscopic hairs. But many gecko species also possess excellent night vision enabling them to hunt prey and navigate in near total darkness.

For instance, the tokay gecko (Gekko gecko) has large eyes with vertical pupils that open widely at night to allow maximum light exposure. Their retinas contain a high density of rod photoreceptor cells optimized for low light sensitivity.

Experiments have shown tokays can still identify colors and catch insects under light conditions when humans are practically blind (Current Biology, 2019).

Other geckos like the house gecko (Hemidactylus frenatus) have impressive night eyesight too. Scientists discovered house geckos feeding on insects are more than 500 times more sensitive to light than humans (Current Biology, 2019).

This allows them to utilize very subtle light cues when hunting in the dark.

Some Other Nocturnal Lizards Can Navigate in Very Dim Light

While most geckos have excellent night vision, they aren’t the only lizards with this ability. Many other nocturnal lizard species moving about in dim light also have specialized eyes.

For example, the Mediterranean house gecko (Hemidactylus turcicus) has retina cells maximized for low light detection. Experiments revealed they can navigate challenging terrain under starlight conditions 100 times dimmer than humans can manage (Current Biology, 2019).

Similarly, nocturnal helmet geckos in the genus Tarentola have rod-dominated retinas making night foraging possible. Some other nocturnal geckos and skinks also demonstrate comparable impressive feats of low light vision (Current Biology, 2019).

Clearly lizard groups like geckos have evolved amazing optical adaptations enabling their niche nocturnal lifestyles.

The Reasons Why Most Lizards Struggle in Complete Darkness

Lizards have evolved over millions of years to thrive in brightly lit environments. Their visual systems are not designed to function well in complete darkness. Here are some of the main reasons why most lizards have a hard time seeing when no light is present:

Underdeveloped Rod Cells

The retinas of most lizard species contain very few rod cells compared to humans and other mammals. Rod cells are the photoreceptors in the eye that allow vision under low light conditions. With few rods, lizards cannot see well when light levels drop.

Only some geckos and night lizards have high densities of rod cells.

Dependence on Cone Cells

Instead of rods, most lizards rely heavily on cone cells for vision. But cone cells require plenty of light to function properly. They are ineffective at capturing and transmitting visual information under dark conditions.

With few functioning rod cells and dependent cone cells, complete darkness leaves most lizards visually impaired.

Lack of Tapetum Lucidum

Many nocturnal animals like cats and owls have a tapetum lucidum – a reflective layer in the eye that amplifies low light. This adaptation allows them to see much better in darkness. However, lizards lack a tapetum lucidum entirely.

Therefore, their eyes are unable to make efficient use of very limited ambient light under dark conditions.

Slow Adaptation of Visual System

When moving from light to complete darkness, the eyes and visual systems of cats, raccoons, and other nocturnal species quickly adapt to maximize use of available light. The visual systems of most lizards do not adapt nearly as fast.

So they suffer from sudden blindness when plunged into complete darkness before their vision can adjust.

Lack of Other Adaptations

Many nocturnal and crepuscular (active at twilight) animals have excellent night vision thanks to wider pupils, increased light sensitivity, and enhanced night vision brain centers. Lizards generally lack these sorts of adaptations that would allow their eyes and brains to better process visual information under very dark conditions.

Conclusion

While a few lizard species like geckos can see fairly well at night, the majority of lizards cannot see in complete darkness. Their eyes lack adaptations for maximizing light capture and sensitivity in dim conditions.

However, crepuscular and nocturnal lizards have better night vision than diurnal species due to differences in eye structure and composition.