Heat And Light
Why Is Heat And Light So Important?
It's helpful to have at least a very basic understanding of the biological processes going on inside your tortoise so that you know the reason why providing access to heat and UV light are so important.
A tortoise will sit outside basking in the sunlight naturally absorbing UV-B whilst at the same time warming itself. Inside the tortoise a chain reaction of processes will be happening. The UV-B from the sun turns provitamin D made in the skin's cells into previtamin D3. The tortoises warm skin allows the previtamin D3 to turn into vitamin D3. The vitamin D3 is then carried by the blood stream to the liver where it is hydroxylated into calcediol. In the kidneys calcediol in converted to a hormone called calcetriol. This is the hormone that plays an important part in calcium metabolism, needed for strong bones and shells in tortoises.
So for indoor enclosures a basking light to warm the skin and full spectrum UV light are essential as they provide a temporary substitute for natural sunlight. This together with a vitamin and calcium supplement will help maintain your tortoise if it needs to be inside during cold weather. It's important to note that UV-B will not penetrate glass and plastics so simply placing your tortoise table near a window is not sufficient. Glass and plastic does work well to use to build a warming area in an outside enclosure though. Of course outside and natural sunshine as much as possible is always the preferred option, with lamps and artificial heat being used temporarily to keep your tortoise active during cooler days and if they need to be over wintered.
Bulbs And Lamps
Nothing beats natural sunlight, so during the summer months outside access is essential. However, in the UK with our shorter summers, reduced daylight hours and cooler temperatures during Spring and Autumn our tortoises don't receive anywhere near the same amount of sun and UV levels as they would in the Mediterranean, so we need to provide extra indoor heat and light for our tortoises at these times. Usually a tortoise will require heat and light for around 12-14 hours per day. Additional heating is not required a night time unless temperatures are likely to reach freezing. As long as the tortoise is in a dry place they can tolerate cold night time temperatures, down to about 8c.
There are two ways of providing the additional indoor heat and light needed. Firstly, there are the popular Self Ballasted Mercury Vapor lamps. This is one bulb that provides heat and UVB light. They need to be fitted into an appropriate reflector holder and should be suspended at one end of a tortoise table at the distance specified by the manufacturer. You should be aiming for a temperature of around 30c directly under the lamp. The temperature at the far end of the table away from the lamp should be around 20c. It may be that additional background heat is required to achieve the 20c.
The second method is to provide separate basking lamps for heat and another that emits UVB light. These should be placed close together because the tortoise needs the both the heat and UVB light together. Never use heat mats for heating a tortoise as this can cause the contents of their stomachs to ferment.