How Important is Natural Sunlight to Tortoises?

Question

My fiancée and I are considering getting a Mediterranean spur thigh tortoise - neither of us have had one before, and we're unsure if it's suited to our current situation - as much as we both love the idea. The tortoise in question is currently 6 months old and is being given away by a friend of my fiancée.

We live in a ground-floor flat with no garden or outside space - however, we do plan to buy our first house (non-negotiably with a garden) within the next 2 years (maximum - we hope less).

We've been told that vitamin D is important for tortoises, especially in early life, and fully plan on getting a UV lamp and a proper "tortoise house" (unsure of the correct term!).

We would rather not get a tortoise at all than selfishly make it fit into our lives at the expense of harming its life or development, so any help would be hugely appreciated!

Answer 1

Natural sunlight is the best source for reptiles to obtain D3 however for indoor tortoises you can use artificial uv lighting. Mercury vapour bulbs are ideal as they pump out a ton of uvb and can be used as basking lights (lots of heat). Taking your tortoise outside for 30mins a day is very beneficial (though the more the better), I would do this on top of having his indoor UV lighting.

Another good option for indoor UV are the long tube lights, the coil bulbs are garbage so don't bother with those.

As tanya had mentioned it is crutial for them to have this as it's how they utilize calcium. You will need to add supplements to his diet as well to prevent MBD (metabolic bone disease) and other health issues, though take caution that you can over supplement and make your tortoise sick. Calcium every second day and multivitamin once a week is ideal (sprinkle on food). You can purchase reptile supplements at your local pet store.

Answer 2

According to this website,

Tortoises synthesise their own vitamin D3 from the UV component of sunlight. Vitamin D3 is essential for the effective metabolism of dietary calcium in reptiles.

...

Carnivorous and omnivorous reptiles get a high proportion of their vitamin D3 requirement from their food, however, plants do not contain D3, cholecalciferol, instead they contain D2, ergocalciferol, which is far less efficient in calcium metabolism than D3.

In summary, this means that since almost all tortoises are herbivorous, they will depend more on the artificial lightning (your UV lamp in this case) to get vitamin D3.

The website goes on to explain that if vitamin D3 is not available, your tortoise could develop a condition known as Metabolic Bone Disease (MBD). In accordance to what you said, yes, younger tortoises are most at risk. MBD could cause the bones to soften in younger animals, especially the long bones.

Lastly... The tortoise house you're referring to, I believe is called the vivarium/terrarium.