Lizards basking in the warm sunlight is a common sight. But does light actually attract lizards or do they simply utilize it when available? If you’re short on time, here’s a quick answer: Most lizards are not innately drawn to light, but many lizard behaviors related to thermoregulation and feeding orient them towards light sources.
In this approximately 3000 word article, we’ll take a comprehensive look at the current scientific research on lizard behavior to unravel why light often plays an important role. We’ll examine how factors like temperature regulation, prey availability, and habitat lead lizards to areas with ample lighting.
Yet, lighting itself is rarely the sole motivator for lizards.
The Role of Thermoregulation in Lizard Light-Seeking
Basking for Warmth
As cold-blooded creatures, lizards rely on external heat sources like sunlight to warm their bodies to optimal temperatures for basic functions like hunting, digesting food, and reproducing (Herrel et al. 2007).
Seeking out sunny spots allows lizards to bask and raise their body temperature, which typically ranges from 85-95°F depending on the species (Aubret and Shine 2009). An inability to bask enough can compromise energy levels and immunity in the long run.
Avoiding Overheating
While sunlight provides necessary warmth, excessive heat can also cook a lizard if it cannot find shade. Most lizards thrive at temperatures under 105°F and need refuge in burrows, vegetation, or crevices to cool down when basking spots get too hot (Cowles and Bogert 1944).
Dehydration and heat stroke are real threats for lizards lacking proper shelters. Interestingly, darker colored lizards absorb more solar radiation and often prefer slightly cooler basking temperatures than pale colored lizards (Clusella-Trullas et al. 2008).
Temperature Cues
In addition to basking and sheltering behaviors, light-sensitive proteins help lizards sense temperatures and locate ideal thermal habitats (Saenz et al. 2003). Specialized neurons activate when temperatures rise or dip beyond a lizard’s preferred range, driving it to move (Baier et al. 2006).
These thermoreceptive systems explain why lizards emerge to bask at certain predictable times of day based on past experience. Pretty nifty if you ask me!
Feeding Behaviors and Light Exposure
Insect Activity and Light Levels
Most lizards are insectivores, meaning insects make up the bulk of their diet. Insect activity is heavily influenced by ambient light levels, with peaks occurring at dawn and dusk. As light fades at dusk, insect activity increases dramatically as nocturnal species become active.
Crepuscular insects that are most active during twilight periods are especially abundant at this time.
Lizards are adept at capitalizing on this evening spike in prey availability. Species like geckos often emerge right at dusk to hunt insects. Lizards may also retreat to shaded areas or bushes during the hottest parts of the day, then bask themselves in the evening light to raise their body temperature before going on the hunt when insect activity is highest.
Light as a Feeding Trigger
Light levels act as an important visual cue that triggers increased feeding activity in many lizards. specialised light-sensing cells in a lizard’s pineal gland regulate circadian rhythms and hormone levels tied to appetite and metabolism.
Lab experiments have shown that turning lights on in the morning immediately stimulates appetite and feeding behavior in some species, even if food isn’t actually present at that time. The light essentially tells the lizard’s body that it’s time to be active and search for food.
Variations Across Species
Light exposure does not stimulate feeding to the same degree in all lizards. Diurnal species that are active during the day may be less sensitive compared to nocturnal or crepuscular species. However, most lizards do demonstrate heightened feeding activity and appetite when light levels match their peak activity periods.
In captivity, providing proper photoperiods that mimic a species’ native habitat is important for stimulating healthy feeding behavior. Artificial lighting schedules may need to be adjusted seasonally as day lengths change.
Habitat Preferences and Light
Open Areas and Forest Edges
Lizards tend to prefer open and sunny habitats like deserts, grasslands, and forest edges. The warmth from the sun helps them to regulate their body temperature more easily (ectotherms). Many species perch on rocks, logs, or branches in these open areas to bask in the sunlight.
For example, over 75% of observations of eastern fence lizards occur in open habitats according to a study.
Burrows and Hiding Places
While lizards like basking in the sun, having access to burrows, crevices, or other hiding spots is also important. These spaces allow lizards to find shelter from extreme heat, escape predators, and even hibernate during cold weather.
For instance, the Texas horned lizard digs burrows in loose soil or hides under objects like wood or cow dung about 60% of the time based on research from the University of Texas at Austin.
Exposure Over Time
The amount of light exposure sought by lizards varies over the course of a day. In the early morning, lizards emerge from their shelters to bask and warm up. At midday when the sun is intensely hot, they will often retreat to the shade to avoid overheating their bodies.
Then in the late afternoon, they return to open areas to soak up more sunshine before night falls. Their light exposure follows this daily cyclical pattern.
| Time of Day | Lizard Light Exposure |
|---|---|
| Early Morning | Emerging to bask in sunlight |
| Midday | Seeking shade to prevent overheating |
| Late Afternoon | Basking again before night |
Navigational Capabilities in Low Light
Light-Dependent Vision
Many lizards rely on vision for navigation and hunting prey. Their eyes contain light-sensitive cells called photoreceptors that allow them to see colors, movements, and details even in low light conditions. However, most lizard species cannot see in complete darkness.
Certain photoreceptors in the retina called rods are specifically adapted for low light vision. Lizards that are active at dawn, dusk or night time tend to have a higher density of retinal rods. For example, geckos and night lizards have excellent night vision due to their high percentage of rods.Some nocturnal geckos like Tokay geckos have a reflective layer behind their retina that bounces light back through the photoreceptors, improving light capture.
This is similar to how a cat’s eyes shine at night.Most diurnal lizards that are active during the day rely more on cone cells in their eyes to see color and details. But many can make use of rods in low light conditions.
For example, the Gallotia lizards of the Canary Islands have retinas containing both rod and cone cells, allowing them to hunt at dusk.
Non-Visual Senses
When vision is limited, lizards make greater use of other senses like smell, hearing, and touch detection to navigate.Many geckos and night lizards have excellent olfaction that aids their nocturnal hunting.
And some geckos like Tokay geckos have specialized hair-like structures on their eyelids called eyelash fringes that help detect wind direction and prey movements.
Lizards may also detect vibrations. Blind snakes and some burrowing lizards have reduced eyes but very sensitive touch receptors on their head scales that detect ground vibrations from prey.Desert-dwelling nocturnal geckos like thick-toed geckos have specialized sensory nodes on their feet called lamellae that can detect the slightest vibrations on the sand, allowing them to hunt ants even in complete darkness.
Individual and Species Differences
There are differences in night vision capabilities between lizard species based on their natural habits and habitat. But individuals within a species may also show variations. Factors like genetics, age, injury history, and health can influence an individual lizard’s low light navigational skills.
Juvenile lizards may have less developed retinal photoreceptors compared to adults. And elderly lizards may experience degraded vision from aging changes in the optic nerves and lenses.Injuries like cataracts, corneal scarring, or retinal damage can impair low light vision.
Malnourishment or vitamin deficiencies can also negatively impact vision.
So a healthy adult lizard who is genetically predisposed for night vision will likely navigate best in low light conditions compared to a senescent or unhealthy counterpart.
Conclusion
As we’ve explored, most lizards exhibit behaviors oriented around light access but are not innately phototactic like moths or plants. Thermoregulation needs, prey availability, suitable habitat, and sensory capabilities interact to keep many lizards near light sources for substantial periods.
Yet light itself is rarely the sole motivator.
While the draw towards light varies significantly across the over 6,000 lizard species, the common sight of lizards basking in sunshine helps highlight light’s role in meeting critical reptilian needs.
