I have never produced tortoises in captivity, but have read some from people who have produced them. The common thought seems to be incubation temps in the mid-80's, and humidity supplied by damp, but not wet, vermiculite in relatively sealed clear plastic boxes. I have not seen anything stating exactly measured humidity levels. However, based on the degree of moisture in their incubation media, and my experience with incubation of other reptile species, I would say that the humidity they are working with would be around 85 to 90%. As I stated earlier, this level of humidity would be in combination with a damp, but not wet substrate. As you are probably aware, a wet substrate will cause major problems with tortoise eggs.

Kelly