Herpetology - the study of amphibians and reptiles

Heating and Lighting


These two subjects are inseparable. Not only is the provision and regulation of both in the correct manner essential to the welfare of your herps but each can produce the other as a by-product - whether desirably so or otherwise. Nonetheless they do serve different purposes and will be dealt with separately.


General. With outdoor vivaria this is more than adequately catered for. Although the length of the day/night cycle in parts of the UK might differ significantly from the wild for animals which will nevertheless cope with our climate, the difference does not appear to adversely affect their behaviour and well-being.

Unheated covered vivaria such as greenhouses have an even greater difference in the day night cycle to that which the animals are accustomed to but nevertheless appear to need no supplementary lighting for the species which can be kept in them. This, however, assumes that a UV transmitting glazing is used. If this is not the case then the provision of a UV light is advisable for the well-being of the animals and is certainly essential to breeding in most lizards. A mercury vapour lamp is probably most suitable in these circumstances.

With indoor vivaria which also have access to sunlight all of these factors continue to apply. I do have supplementary lighting using ordinary fluorescent tubes but this merely allows me to see the animals which are normally asleep by the time daylight fades. Conversely, nocturnal animals are usually active. This reflects an important fact - such sources of light are truly insipid compared to natural sunlight even on hazy days. In this context, the timing of lighting should be regulated either through timers or manually to ensure a day-night rhythm.

Traditional Indoor vivaria usually rely totally on artificial light. In such cases the quality of the light in terms of both brightness and wavelength must be considered. Since such vivaria are comparatively small, the lights are much closer to the animals and so long as they do have a reasonable output which can and should be boosted by a reflector they will be sufficient to represent daylight. In such cases for most species a UV transmitting light is essential and there are several makes of fluorescent tubes and compact bulbs which can provide this. They do, however, need to be close to the animal - between 15 and 30 cms for the UV output to be sufficient. While some species need little, if any UV, I have found no species that suffers from being under a relatively low output UV source such as this. Larger vivaria, especially with even more UV dependent species can benefit from UV transmitting mercury vapour bulbs. Well designed bulbs of this type are the only ones that can generate a UV output approaching that provided by the sun.

More details of lighting sources.

"Domestic" and Aquarium fluorescent tubes.

These can be suitable as light sources where their only purposes are to allow us to see the animals or to represent a day-night rhythm for nocturnal or crepuscular animals. Even so, many of them give rather strange shades of lighting and it is a reasonable generalisation to say that only those that produce a bright white light should be used. I find they can be mounted within a vivarium without risk of the animals burning themselves on them but an external ballast such as sold for aquariums must be used.

Ordinary Light bulbs

Not recommended as light sources at all. Not only is the light colour wrong but they can also present a strong and undesirable temperature source.

UV transmitting fluorescent tubes and compact fluorescents

While these do have their limitations in terms of light and UV output they can be extremely useful and I use them extensively. Again, an external aquarium ballast should be used (apart from compact fluorescents which are self ballasted) and I have found no problems with animals burning themselves on them. As previously stated, their UV output is quite low and animals do need to get close to them to benefit. I find, however, that in all vivaria a roof mounting is fine if the vivarium itself reflects the animals requirements. In other words, if the animal is arboreal it will naturally climb the branches which are provided to gain access to the light. Similarly, if it is a terrestrial animal the vivarium should be much lower with, for example, a rock placed under the fluorescent to allow the animal to get close enough.

One of the limitations of these fluorescent is their lifespan. Although they will give good quality visible light for as long as any other fluorescent, the UV output falls rapidly. There seems to be some inconsistency between individual fluorescent of even the same make in terms of the speed of this decay but it is safe to say that you can no longer rely on output being sufficient after 6 months.

Mercury Vapour Bulbs

These have long been the mainstay of herpetologists keeping animals with high UV requirements. Their UV outputs are quite substantial and the rate of decay much slower than fluorescents. Unfortunately they are far more expensive to both buy and run. However, so far as capital outlay is concerned because of their increased lifespan they actually work out no more expensive over time than fluorescents.

Recent advances have resulted in the Mega-Ray, an MV bulb designed very specifically to meet the UV requirements of reptiles. With this example it appears that other manufacturers are beginning to follow suit.

Bulbs in this series are the ones that can approach the actual UV output of the sun and it has to be said that basking reptiles seem to love them and benefit enormously from them. They should be used with a polished metal reflector to maximise their effect.

They also generate quite considerable heat which can cause problems. It is undesirable to have them constantly switching on and off as their brightness can leave the animal confused regarding day-night rhythms and, of course, it lessens the bulb's life span. This can be addressed by limiting the number of hours it is on and good vivarium design ensuring that the other end of the vivarium remains cool. Since the vast majority of lizards bask primarily in the first few hours of the morning and the last few of the evening I have these bulbs on for 2-3 hours in the morning from about 0700/0800 - 1000 and similarly in the afternoon from 1500/1600 - 1800.

In addition, since they do get so hot, it is necessary to ensure that the animals cannot get too close or touch them. In some case they can simply be mounted beyond the animals reach but more often it is advisable to cover them with mesh. This should be as coarse as possible to maximise the light transmission. A fine mesh can easily reduce it by 50%.

It is also extremely important to ensure that light sources are above the animal just as is the case with the sun. Strong light sources, especially those including the essential UV wavelengths can cause photoconjunctivitis if they shine directly into the animal's eyes.

More about UV.

Rather than continuing to go on about UV and light quality I would simply reiterate that it is essential to most basking herps for the synthesis of Vitamin D3, itself essential to proper bone formation, general health and well-being, and successful breeding. You can learn far more about the qualities of the UV output from many different forms of light by visiting here and about the animals requirement's here. Both of these valuable online resources are highly recommended.


General. Again with outdoor vivaria heating is not necessary - presuming of course, that you keep only suitable species. Should you choose not to please don't ask me how you can heat an entire outdoor reptiliary without attempting to heat most of the known universe as well !

Covered outdoor vivaria such as greenhouses are a little different and certainly more practical to heat. I certainly do not heat mine, but since on the south coast of the UK the temperature within the greenhouses never drops to freezing point and remains significantly higher in the hibernacula I do not need to. While I can make no firm recommendation I think that an electric tubular heater running from a frost stat might be practical where there is a risk of temperatures dropping too low in the winter. Obviously care would be required as the heat loss through the glazing would be considerable.

Indoor walk-in vivaria present a special problem as there is a very large area to be heated and the species typically kept in them require higher temperatures. In my case this is provided by a central heating system with individually controlled radiators for each vivarium providing ambient heat at different levels for day and night. Since these also provide a hotspot where the temperature is considerably higher and sunshine is frequently available this takes care of all the heating requirements.

Indoor vivaria become even more complex. Again, in my case the reptile room itself is centrally heated and this provides a suitable background temperature. Each vivarium also has its own separate heating switched through thermostats. This heating is generally provided by a spotlight for basking during the day. At night a more diffuse warmth at a lower temperature is provided by a red "Fireglo" bulb. This is omitted from vivaria where the ambient room temperature is sufficient at night. Conversely, some vivaria which contain non basking species have only the red light operable both day and night albeit at different temperature settings.

As briefly mentioned in the heating section, one very important aspect is to ensure that a vivarium has an adequate temperature gradient. In essence, a basking spot should be provided where the animal can quickly raise its body temperature to an appropriate level (in most species, about the same as ours). It should, however, also have cooler retreats which also avoid any UV radiation. Consequently it is usually best to concentrate both heating and UV sources towards one end of the vivaria.

For both types of indoor vivaria, by wiring these through appropriate timers, thermostats and relays, it is possible to control the temperature adequately during both day and night at the differing levels necessary.

Other heating sources. As you will gather from the above the only heat sources I use are white or red light bulbs, sunshine and radiators. All but the last, to my mind, most closely emulate the natural heat sources which the animals use in nature. In essence throughout most of the day they are reliant on radiant heat from the sun (or, additionally in this case, light bulbs) which they absorb. along with UV, through their dorsal surfaces. Later in the day this may be supplemented by the heat radiated by rocks which they have absorbed from the sun. In this case, even the radiators start to emulate nature since they all have a rock basking surface above them. I do not find any need to use "heat rocks" or heat mats, neither of which, to my mind, fully emulate natural heat sources.

Wiring. Obviously some of the wiring systems I use are rather complex. I set out an example below but I must stress that you must be confident (and justifiably so) of your capabilities before you undertake this and you should also take into account the legal position regarding electrical work wherever you are.

This example relates only to the wiring for the central heating for the reptile room walk-in vivaria and the lighting for the latter. Only the "Live" wires are shown for clarity.

Some explanation of this diagram is in order. Mains supply in red comes in at the top left and is protected by a switch and a fuse. There are two outlets from this. One, still in red, goes through a timer and a light sensitive switch to lights which thus come on only during the daytime if natural light falls below certain levels. The second, in brown, goes through an overheat protection thermostat set at 35 deg C. This ensures that if the ambient temperature goes above 35 deg C then the whole heating system shuts down. The remaining red wire switches on the day/night relays. Returning to the brown wire, immediately after the overheat protection thermostat it again branches. One branch goes through a second thermostat which switches the boiler on to ensure that the minimum ambient temperature is held at 16 deg C. This continues, in orange, to the output side of the heating valves thus allowing the boiler to be switched on if any one of their thermostats is calling. The second branch provides power to the switched input of various motorised relays and valves that operate the heat sources and to the input sides of the local (vivaria specific) thermostats. In some cases these are in pairs - one for day and one for night. Where this is the case the power goes to the daytime ("hotter") thermostat.  The purple wires interconnect the various relays and thermostats.

Using the extreme left hand grouping as an example, during the day if the ambient temperature is below 35 then power is fed into the input side of the high temperature thermostat via the relay 1 which has been switched on by the timer. If this is calling (i.e. temperature below required level), the power then goes directly to a motorised valve which opens the radiator and switches on the boiler via its own relay. It also connects to a second switch on relay 1 which feeds the optional basking lights.

During the night power is fed direct to the low temperature thermostat. When this is calling, this connects to the input side of the high temperature thermostat. Obviously if it is cool enough for the low temperature thermostat to be calling then the high temperature one will also be calling. This time, however, while its output will still operate the radiator valve and boiler, since relay 1 is now switched off (being controlled by the timer) power does not get through to the basking lights.

Last, but not least, it is possible, especially first thing in the morning, for both the low and high temperature thermostats to be calling simultaneously for a while. This does not matter at all since it simply closes a contact between two live feeds and the output remains identical to normal daytime output.

This wiring system allows differing day and night temperatures together with two independent heat sources according to the time of day and supplementary lighting during the day only when necessary.

This is the photo of the actual control box to which this wiring diagram relates. The fused switch and timer are mounted outside the door which is swung open to the right. Obviously this is normally secured shut in view of the potential for electric shock! It is also only one of several such controlling differing groups of vivaria as appropriate to them.

You have been warned!

NEXT: The animals themselves - feeding