Hi Laura,
It is very interesting about your breeder. I don't know any breeder who would sell tortoises of two different species to someone, if they weren't going ot keep them separate, and also I'm afraid the theory about UV light causing excess growth is just not correct.
There are two main types of UV light -- UVA and UVB. Tortoises should have both, but UVB is the really important one. The main (and best) source of UVB is from the sun, and it reacts with the tortoise's skin and enables it to produce Vitamin D3. Vitamin D3 enables the tortoise to absorb and utilise the calcium in its diet, and calcium is super important for supporting healthy bone and shell growth (and when you think about it, they have an awful lot of bone and shell). The same process happens with the sun in humans, and it's why doctors now say that people in the northern hemisphere (like the UK) should take Vitamin D supplements, because we don't have enough exposure to the sun and for a good part of the year it is lower in the sky and therefore at not such a good angle, so most of us suffer from Vitamin D deficiency. It has nothing to do with the rate of growth -- it ensures that the bone and shell that a tortoise produces is healthy and strong (and in humans it can support the immunity system).
The behaviour that Elvis is showing is typical male mating/dominance behaviour, but you can sometimes get that with female tortoises too. If yours are really less than two years old (it should say on the Article 10 certificates that the breeder gave you when you bought them), then it is probably too early to sex them, but because they are the size of an older tortoise, we might be able to do this. Could you send photos of the undersides of the two tortoises, clearly showing the tail? As I said, it's probably too early, but it might be possible.
Given that it looks like they will need to be separated for various reasons, would you consider keeping one of them and rehoming the other? The Spur Thigh will grow to be much bigger than the Hermann's.
Regarding an outdoor enclosure -- tortoises really thrive outdoors, but it needs to be warm enough for them, so they can't live outdoors all year round without a good source of heat. If you can wear a t-shirt outside then tortoises can go outdoors, and the natural sunshine is very good for them. You can make an outdoor enclosusre secure from dogs by putting a lid over the top of it (a wooden frame covered in chicken wire or something can work well. You are right to be concerned about dogs and tortoises together, but with care you can protect a tortoise from a dog.
I can tell that you really care about your tortoises, and I think you could provide a good home for them. I understand the difficulty in keeping two of them separately, but If you would like to keep one of the tortoises, we would be really happy to support you in any way we can. There is so much involved here -- would you like to have a chat on the phone about it? I could ring you at your convenience, or I could give you my phone number and you could ring me -- just drop me an email at
nina@thetortoisetable.org.uk if you would like to do that. Sometimes it's easier talking rather than writing.
Best,
Nina