6 Things About Bearded Dragons

6 Things About Bearded Dragons

Vision and the 'Third Eye'

Bearded Dragons are long-sighted, with typical prey eye positioning for an enhanced vision field at the cost of depth perception as well as the capability of independent eye movement, such as looking forward on one side and back with the other.

Their colour wavelength acuity is better than a human's, along with a broader spectrum due to being tetrachromatic (they have four cone cell receptor types). Hence, they are high-light sensitive at the expense of poor night vision. This extra cone type allows them to see Ultraviolet waves, emphasising the importance of adequate brightness intensity for their eye health, sleep, and stress + immunity.

Beardies have a parietal eye, a.k.a. the pineal/solar eye organ. It looks like a little spot on top of the skull, which is covered by a thin transparent grey skin/scale layer - except it's a hole connecting to the pineal gland. The eye has no processing ability for visual imagery, whereas it's essential for thermoregulation, the circadian rhythm, navigation and predator detection.

As the structure is receptive to subtle changes in luminance from above, it aids navigation/orientation (sort of like a mix between a sundial and a compass), distinguishing shade, dim light and bright light - where darker areas are likely cooler and lighter ones are warmer. The pineal gland secretes melatonin according to light levels for circadian rhythm regulation, deducing the time of day (e.g., darker light is sleeping time since they're diurnal - lights in captivity should get turned off).

Sudden shadows above are probably frightening, plausibly being a flying predator in the wild, yet resembling one concerning captivity - so best not to approach overhead. Flickering lights, excessive light intensity, or abrupt changes from natural to artificial lighting causes agitation regarding both physiology and temperament.

UV Lighting

Metabolic Bone Disease (MBD) is the most common health issue for beardies. It involves a lack of calcium, phosphorus, vitamin D, or imbalances relative to one another. Domesticated ones need sufficient exposure to UV type B lighting, injections or oral supplementation, preferably UV B, as it's the most manageable and least stressful.

Vitamin D synthesis from UV B is paramount for promoting calcium absorption provided in their diet, so MBD and hypocalcaemia are averted. Enough calcium intake upholds biological and physiological functionality, for example, to avoid rapid muscle spasms, tremoring, seizures and bone fragility after calcium gets taken from them.

UV type A intensifies colouration, respecting breeding appeal; while promoting basking, feeding and general mental/physical health and wellbeing. Dominant beardies can actually lie on top of others for elevated UV absorption.

UV lighting isn't ample enough as a heat source, so a lighting area dedicated to warmness and basking is ideal.

Sociality and Temperament

Bearded Dragons are known for being some of the most chilled reptiles, especially older ones. They are frequently sedentary, particularly while basking in warmth. More calm/relaxed ones have their scales lying flat with a silky touch, and the 'beard' plus upper chest should be similarly coloured to the rest of the body (unless recent shedding reveals a new colour).

The 'beard' is formed by projecting spines under the neck, which can puff/expand to appear bulkier and spikier if excited, or as an attempted deterrent. The neck and chin are usually raised, with an open mouth, body tension, and maybe some hissing in contention against predators.

Beard spikes alongside the rest of the skin can change colour from light yellowish to darker black/grey in more intensive states, for instance, discontent, frustration, stress or arousal. Front and ventral side colour change links with social communication, whilst the rest of the skin is more consistent with camouflage and thermoregulation.

More evident communication forms include a human-like greeting, waving a forelimb in a circular arc laterally for species/familiar individual recognition. It can get used interspecifically, probably with less success pertaining to reciprocation/comprehension from the other species. Waves function in hierarchical establishment too.

Beardies' head bobs (similar to pushups) are more often associated with hierarchy - they can be quick, 'challenge' bobs that can get accompanied by fast waves, performed by the alpha or by competing males until one stops. Otherwise, a slow bob and/or slow waves indicate submission or passiveness, attempting to prevent confrontation. Bobs additionally apply to courtship, where males bob frantically, and females may respond slower in acceptance.

Ectotherms

Ectotherms are cold-blooded animals and/or invertebrates. They are highly dependent on external heat sources such as solar radiation to maintain their body temperature above the ambient temperature. As their temperature equilibrates correspondingly to the environment, their temperatures are volatile - yet less thermoregulatory precision may allow them to remain more adjustable to changing conditions.

Beardies and other reptiles have slower-moving, cold blood, alluding to lower metabolic rates, inferring less required food intake to survive longer without eating. It also means they are a low-maintenance species in captivity, except being unable to sustain high-energy activity for too long.

Because beardies naturally live in hot and arid australian woodlands, deserts, scrublands and savannas, they alter their behaviour for temperature regulation via locomotion/shuttling from place to place. Shading, moving into water, burrowing, and even rostral positioning away from heat sources can help with cooling. Moreover, considering their colour-changing abilities, they can switch to a lighter colour for improved heat reflection.

Beardies are unlike endotherms (warm-blooded animals like mammals and birds) who thermoregulate more internally, where temperature fluctuates within narrower limits. They utilise metabolic processes; or mechanisms for heat loss or preservation like sweating, panting, vasodilation, shivering contractions and vasoconstriction.

Despite that, if not a short yawn or aforementioned defensive/confrontational display, beardies can mouth gape as a substitute for panting to increase heat transfer effectiveness away from the lizard. It's proposed to contribute more to head temperature, implying prioritisation of preventing death by the brain enzymes from denaturing. Head-body temperature differences often exist in arid-dwelling reptiles - so the head could feel cool compared to the body.

Water Conservation

Birds, insects and reptiles like Bearded Dragons excrete uric acid as nitrogenous waste compounds that erode your car. It's a paste-like substance, so water volume is lessened for retention, helping them in their arid climates.

This waste form also saves energy since there's no expenditure converting urea to urine (by adding water), as what occurs in mammals. For scaleless silkback beardies, the uric acid mechanism is especially crucial as they lose water evaporatively ~2x as fast as fully-scaled wild types.

Furthermore, it's vital because animals like reptiles only have the shorter 'cortical' kidney nephrons, which don't extend as much as 'juxtamedullary' ones; therefore, they are less capable of filtration and less water gets retained. So, beardies can't produce hyperosmotic urine (fluid with higher salt and nitrogenous waste concentrations - but with less water loss for higher efficiency).

Be careful of salmonella bacteria and possible endoparasites that pass through from the digestive tracts, getting on their skin and then transferring to humans with physical contact.

Mobility

Beardies are technically semi-arboreal; they can climb trees for greater sun ray exposure, assert dominance over other beardies, or if food is only available up there.

On the ground, however, they have a seemingly contradictory evolutionary development. With their centre of gravity residing towards the back of the body already, the distribution shifts further back when running. It might help with propelling power for speed, with less impact on the front limbs for agility and longevity, though more speed with said centre of gravity entails it's tougher to keep the forelimbs on the ground.

Thus, they are pulled back onto the hindlimbs and run on two legs which may have hindered their top speed of ~9mph. They would presumably be faster with all four limbs on the ground. Although, they can sleep standing up with the hindlimbs locked out to the sides, which looks quite funny.