Reptile: Shade dwellers

Reptiles and amphibians, like all animals are highly adapted to life in the wild state. Vast periods of time have passed within this long process of slow adaptation, leaving us with each species as we currently see it. I do not refer to the evolutionary process of species change at a fundamental level here, but rather the latter stages of the developmental journey that allows every species to carry on with intricate change so that it is able to take everything that it needs to thrive within its own preferred habitat as this also develops. Fish to bird is one thing, but adapting to life on an ever-ongoing basis is quite different. It could be viewed as a process of constant ‘fine tuning’.

Reptiles are generally classed within three main activity groups, those being diurnal, nocturnal and crepuscular. In fact there are a myriad of crossovers, adaptations and species alterations between the classic groupings. You cannot class all diurnal species as being direct baskers, allowing exposure to full-spectrum terrestrial daylight in its strongest times in open terrain, as we know that there are plenty of other diurnal species such as chameleons that are daytime baskers but do so within the protection of canopies. Each species has changed and adapted to life within its own portion of the habitat in order to make the best use of it, ensuring that it remains as safe from predation as possible. We class these as being ‘micro-habitats’.

It is vital that every layer of a habitat has the correct balance of inhabitants.  This is core to the ongoing success of the wider habitat. This is why multitudes of species occur at every level from the subterranean to open exposure and show adaptations within that microhabitat to allow it to do so. You cannot have an environment where every species of reptile lives in the canopy or out in open terrain, or the lower reaches would be wastelands, either unchecked and/or without predation of pest species.

As such we have a rich world, filled with life at every level. Within these habitats live a multitude of species, all developed in order to thrive. It has been assumed for far too long that reptiles are only ever diurnal or nocturnal. As such whole groups of animals have had care advice given that does not replicate the natural cycles or methods of energy supply of the species. We have overlooked intricate need via general assumption and based this assumption off of data provided by locals and trappers over a short period. There is still much to learn and we can only learn by taking guidance from the wild habitats and the parameters of supply that exist within it. The fact that MBD is still seen is testament enough to assume that we do not know everything and that we are not always providing for every cycle within life properly.

Over the past decade we have begun to accept that many species are actually better classed as being crepuscular, or more often seen during dawn and dusk. In reality, we do not know enough about many of the species that we keep to even label them as being only ever active close to sunset. There are many reports of species that have been previously classed as being nocturnal such as Moorish Geckos, being seen regularly foraging or resting in very high light levels during the day in the wild. We must realise that daylight contains a wealth of energy contained within its photons, and that this energy is freely available, as and when any animal requires it.  

The word crepuscular may not mean anything to most of us, it is not a common word and can lead to some confusion. The word is used to describe animals that are more often seen as being active at dawn or dusk. This is a time of day where heat levels are either rising or falling and light levels are lower, thus reducing the risk of open predation and water is available. Whole groups of species have developed to live within these times and it is vital that we follow the pathway of the theories of wild re-creation and natural-balance in order to help supply for their wild-like needs.

Most crepuscular species show a high level of adaptation within the body. Many of these developments can be seen by the eye and have aided in their historic classification. For example, lizards that are more active in lower levels of daylight generally have much thinner skins and a degree of dark colouration. They usually have adaptations to the eye, to allow them to see well in low light levels and they usually live within burrows, rock networks, branches, caves, in the deep canopy and/or within the first layer of the substrate. They tend to hide from the high heat and predation risk of the day and then emerge when the period of high risk has reduced.

These all have one thing in common, they are skulkers, hiders and creepers. They are well adapted to life in the underworld, a world of shadows and seclusion. They are the shade dwellers and are very good at what they do.

It has been assumed that a species with an interaction with small quantities of, or infrequent access to unfiltered daylight, does not need to be exposed to it, this is wrong. Reptiles are ectothermic, powered by an external source of energy, namely full-spectrum terrestrial daylight. It is by being exposed to the infrared spectrum that they obtain the energy that they need to be able to function, move and feed. This is a core function and one of balance.

We seem to only ever think of the levels of energy that are available to us in our own home country rather than that of the wild habitat of the species that we keep. Energy levels within daylight are very much higher in many of these habitats than those that we experience in the UK and as such even as the light is decreasing or increasing, the level of available energy within that light is surprisingly high. The fact is daylight is a full-spectrum from UV-B to IR-B projected down onto us from the direct source, this does not change. You cannot be exposed to direct heat without being similarly being exposed to visible light or terrestrial UV. It is all one source and it is balanced, whatever the quantity. If there is enough light to see your hand in front of your face there is enough light to have a measurable level of energy. It is within this balance that our shade dwellers find the energy that they need to power their bodies.  

They may have developed to be more active within low levels of light, but by being exposed in some way, no matter how slight, they are exposed to all of the terrestrial wavelengths of the sun as a filtered source.  As per the laws of development over time, there will be a use for and a level of protection against this energy and every other parameter of supply that is available to them.

As we have seen, many of these species have developed a very thin skin. This thin dermal layering allows light to interact with the body very quickly and in low levels. In reverse, a fully diurnal open basker would have a very thick, almost armoured skin. This provides a high level of protection to the animal from the sun in high quantities and for extended periods. Both animals are using the sun in the same way, but within the process set out by its own development.


We can see easily from blood testing that these thinner-skinned animals are as able to generate vitamin D3 in the natural and self-regulated cycles as the thicker skinned open baskers. They simply go through the process in a fraction of the time and in lower levels of light. This provision of D3 then allows them to assimilate, store and use mineral nutrition which to a degree sets and allows for the function and health of every single organ.

The move towards providing energy from light for this group has been rather slow to date but we are now seeing the old ‘it doesn’t need UV’ argument disappear as keepers gravitate towards a more natural method of supply. A quick search of the keeper’s forums will show a marked swing towards those that use UV products now.

With every species light and its contained energy must be provided in the correct way. This means providing a quality of light that replicates that of the terrestrial source and in a quantity and method that aligns with the species’ own method of use. To do this we must always provide illumination from above the animal, never to the side as this bypasses the developed extended orbital bones and increases the risk of glare related disease. We must only provide a lamp that’s energy projection will match that of the area in which the animal is found. Providing too much energy will result in burns and too less can mean either unnaturally long basking or an under provision of D3.


We must also use the principles of the light and shade method for every species. No animal is subject to the power of the sun for the whole of the day without having an area in which it can find shade and rest. Even the open baskers will have burrows, rocks and even fallen branches to hide within. The cycles that produce D3 are self-regulating in a number of ways. Firstly, via the correct exposure to UV-A which can turn off or recycle production, and then via active self-regulation of the body within the habitat and between energy gradients. We must ensure that every species is able to self-regulate well between light and shade and the millions of index changes in between the two.

This is a point of note, an animal is able to take exactly what it needs at any given moment from the energy that surrounds it. It does this by altering its level of exposure by moving the body within the natural light gradients that exist in its home terrain. Many animals can even move to higher areas in order to assimilate higher quantities of energy. It is via this horizontal movement within the intricate terrain and via vertical self-regulation that any species is able to regulate itself in some way. Light is never on or off, but rather an uncountable series of shafts and reflections of infinite degrees of size and angles. This is core to natural self-selection and regulation and they are more than capable using it, if we provide adequate space and decorative design.

Shade dwellers are able to move within power gradients or find provision by only exposing part of the body to direct light while the majority of the body is hidden within the security of the basking place. This is called partial basking. A thinner-skinned animal can go through the D3 production cycles even when only exposing quite a small area of the body. This is a fantastic adaptation and one that was first researched in the 1960s. This is a high level of development, being able to secrete oneself within a habitat while only exposing a small part of the body and still being able to power up correctly.

Within all of this we must also factor in the benefits to both body and mind. An animal that has access to a well decorated enclosure that also allows it to regulate its own level of energy will have to move to do so. This means the implementation of physical enrichment which in-turn increases brain function. Exposure to UV-A will activate natural reptilian vision which in turn lowers potential stress and allows a more natural view of life. The mind and the body is nourished via both exercise and natural stimulation.

If we glance back for one moment to the three parameters of supply that make up overall nutrition we can easily see that providing the correct level of exposure to external energy falls within active nutrition.

  • The energy which surrounds
  • The energy which is ingested
  • Physical and mental enrichment

Each of these parameters are bound into the next in deep synergy, all working together in order to allow the correct level of biological function within an animal. A well energised but poorly fed animal is as unbalanced as a well fed but under energised animal.

As always, all of the answers to great animal care are hidden in the wild animal, all we have to do is to learn from it and then implement these things in a safe and measured way. This is the key to effective and ethical reptile care.

John’s book was published in Spring 2018 and is currently available in all good bookshops, online and through the reptile wholesale network and a trade price. This will be a series of titles based on the elements.

To listen to John’s free podcasts, visit www.chameleonbreeder.com/podcast-ep-55-mbd-uvb-with-john=courteney-smith

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