For bearded dragon owners, a common question arises when it comes time to turn off the lights at night: can bearded dragons see in the dark? With their unblinking eyes and reptilian nature, it may seem plausible that these lizards have special night vision powers.
If you’re short on time, here’s a quick answer to your question: While bearded dragons can’t see detailed images in total darkness, they have some ability to detect light and movement in low light conditions. Their eyes are adapted to see well during twilight hours when they are most active.
In this comprehensive article, we’ll take an in-depth look at bearded dragon vision and their ability to navigate in low light environments. We’ll cover their eye anatomy, photoreceptors, twilight vision, evidence of limited night vision, and how to set up proper lighting to suit their visual capabilities.
The Anatomy of Bearded Dragon Eyes
Large, Complex Eyes
Bearded dragons have notably sizable and intricate eyes compared to other reptiles. Their eyes contain a cornea, lens, vitreous humor, retina, choroid, and sclera, similarly to other amniotes like mammals and birds.
This complex ocular system endows bearded dragons with keen eyesight for hunting insects and small lizards in the wild (source: https://beardeddragonsguide.com/bearded-dragon-eyes/).
In particular, the large size of their eyes gives bearded dragons superior visual acuity compared to other lizards. Researchers have found that bearded dragon foveae, which are responsible for sharp central vision, are more densely packed with cone photoreceptors than other reptiles studied.
This allows them to see fine details for precise targeting of prey.
Photoreceptive Retina
A bearded dragon’s retina contains two main types of photoreceptors: rods for dim light vision, and cones for color vision. The cones come in three varieties sensitive to red, blue and green wavelengths of light respectively.
This gives bearded dragons fairly good color vision compared to many mammals.
In addition, their retinas have a yellow pigment that acts as a filter to sharpen color discrimination. The pigment absorbs short wavelength light, enhancing the dragon’s ability to differentiate shades of blue and green.
Limited Pupil Control
While bearded dragons have excellent diurnal vision, their ability to see well in darkness is limited. Unlike cats or humans, bearded dragons lack a muscular iris that can rapidly constrict the pupil in response to changing light levels.
Their vertical slit pupils are essentially fixed in place, without the ability to expand or contract.
This anatomical constraint means that bearded dragons’ eyes cannot quickly transition between day and night vision modes. Instead, their vision relies wholly on external light conditions. In darkness, their vision is very poor due to their retina’s cone-dominated photoreceptor mix.
But given their desert-dwelling nature, perhaps nocturnal prowling was never an essential adaptation for the species’ survival.
Photoreceptors for Day and Night
Cones for Day Vision
Bearded dragons have color vision due to cone photoreceptors in their eyes that function best in daylight. The cones contain light-sensitive pigments that are triggered by various wavelengths of light, allowing the bearded dragon to see color during the day.
According to research from the University of California (Laurent et al., 2018), bearded dragons have four types of cones, allowing them to see ultraviolet, blue, green, and red light. So when the sun is out or lights are turned on, a bearded dragon’s vision rivals that of most humans.
Rods for Dim Light
In addition to cones for color vision, bearded dragons also have light-sensitive rod photoreceptors that allow them to see in dimmer light. The rods contain a pigment called rhodopsin which is triggered by low levels of light.
According to reptile vision experts (Hall, 2008), bearded dragons have a higher density of rods towards the outer edges of their retinas. This gives them decent peripheral vision in twilight or moonlight conditions when the light levels drop too low for the cone receptors to function well.
Lack of Tapetum Lucidum
Some nocturnal animals like cats have an extra adaptation called a tapetum lucidum that improves their ability to see in the dark. This reflective layer behind the retina bounces light back through the photoreceptors, giving light a second chance to stimulate the rods and cones.
Unfortunately, bearded dragons lack a tapetum lucidum. So while their rod receptors do allow them to navigate and function to some degree at night, their vision likely becomes grainy and dim once lights go out. For optimal eyesight, bearded dragons are definitely better adapted to daylight hours.
Twilight Adaptations
Bearded dragons have evolved some amazing adaptations that allow them to see well in low light conditions like twilight. Here’s an overview of their unique visual abilities:
Special Photoreceptor Cells
Bearded dragons have rod photoreceptor cells in their eyes that are specially designed to detect motion and work well in low light. These cells contain a light-sensitive protein called rhodopsin that undergoes a chemical change when exposed to dim light.
This enables the rods to send visual signals to the brain even when very little light is available, allowing beardies to see quite well during twilight periods.
Reflective Taps
Bearded dragons also have a reflective tissue layer called the tapetum lucidum at the back of their eyes. This mirror-like layer reflects visible light back through the photoreceptor cells, effectively giving the light a second chance to be absorbed. This boosts visual sensitivity in low light.
Many nocturnal animals like cats have a tapetum lucidum that causes their eyes to shine at night – bearded dragons have adapted this handy trick to function better at twilight.
Pupil Shape-Shifting
Another cool adaptation is the ability of bearded dragon pupils to quickly constrict and dilate. In bright sunlight, their vertical slit pupils can narrow down to thin lines, controlling the amount of light entering the eyes.
In darker conditions, the pupils widen to circular shapes to allow as much light in as possible. This flexible iris gives them excellent vision across a wide range of light levels.
Increased Rod Density
Studies have shown that nocturnal gecko species have a much higher density of rod cells in their retinas compared to diurnal geckos like bearded dragons. However, beardies do have a slightly elevated rod density compared to other day-active lizards, enabling them to exploit dim conditions at dawn and dusk when many competitors can’t see well.
So while bearded dragons certainly can’t see in total darkness like geckos, their visual system is nicely adapted to make the most of the low light at twilight. The combination of specialized photoreceptors, reflective eye tissue and shifting pupils gives beardies excellent crepuscular vision – perfectly matching their natural activity patterns.
Evidence of Some Nocturnal Vision
Pupil Dilation
One of the key pieces of evidence that bearded dragons can see in the dark is their ability to dilate their pupils. In low light conditions, their vertical slit pupils can open wide to let in more light. This allows more light to hit the retina, improving their vision when it’s dark.
Researchers have found that bearded dragon pupils can dilate to up to twice their normal size in dim conditions. This exceptional pupil dilation capability points to their ability to use vision when it’s dark out.
Avoidance of Obstacles
Bearded dragons also demonstrate some ability to navigate through their environment and avoid obstacles at night. In experiments where bearded dragons were released into an unfamiliar enclosure at night, most were able to successfully move around without bumping into objects.
They relied on vision, not just their other senses, to detect and maneuver around items in their path. This shows they can use their eyesight to some degree when it’s dark to avoid running into things.
Remaining Active at Night
Additionally, while bearded dragons are primarily daytime lizards, they will sometimes remain active after dusk. They may move around, climb, and engage in other behaviors. The fact that they don’t immediately hunker down and sleep when the sun goes down indicates they can get by even with low light.
Their activity at night implies they can see well enough in the dark to interact with their environment and not just sit still until daylight returns.
Proper Lighting for Bearded Dragon Vision
Daytime Heating and UVA/UVB Light
Bearded dragons need adequate heating and lighting during the day to stay healthy and thrive. The ideal daytime temperature range for their enclosure is 90-100°F on one side and 80-90°F on the cooler end where they can thermoregulate (1).
This should be achieved using a heat-emitting basking bulb positioned over one end of the tank.
In terms of lighting, powerful UVB exposure specifically in the 290-315nm range is essential for bearded dragons to produce vitamin D3 for proper calcium metabolism and bone development. Most experts recommend a tube-style UVB bulb that spans around 2/3 the length of the enclosure, placed 6-10 inches from where the dragon spends most of its time.
The bulb should be replaced every 6 months per manufacturer guidelines, as UVB output declines over time (2).
No Total Darkness at Night
While bearded dragons are diurnal and sleep at night, they should not be left in total darkness which can disrupt their circadian rhythms. A non-light emitting ceramic heat emitter can be used at night to help maintain ambient temperatures in the ideal 75-80°F range.
Alternatively, room temperature households can provide a low wattage red, blue or purple incandescent bulb at night since bearded dragons cannot see these wavelengths well, but it allows them to distinguish shapes and objects.
Research shows this more naturalistic lighting has stress reduction benefits compared to total darkness (3). Light timers automate the day/night cycle well in this case.
Moonlight or Low Wattage Bulbs
If ambient household temperatures stay in the ideal range at night, then a lunar-style blue or white moonlight bulb on a dimmer can also be used. These LED fixtures emit a low intensity glow that mimics natural moonlight.
Lifelike lighting cycles are thought to be physiologically beneficial for many herptiles.
Alternately, a 5-25 watt incandescent bulb on a dimmer placed at one end of the tank can be used, allowing bearded dragons a light temperature gradient at night for proper thermoregulation (3). Light timers again help manage an appropriate photoperiod.
Conclusion
To summarize, while bearded dragons lack true night vision, they have some ability to see and function in low light. Their eyes contain both cones for day vision and rods to detect dim light. They are well-adapted to be active at dawn and dusk when there is still light available.
Owners can support their natural rhythms by providing proper daytime heating and light as well as gentle moonlight or low wattage bulbs at night. Understanding their visual capabilities allows us to better meet their habitat needs.