One rather incredible ability that tortoises possess is that of regenerating and re-growing not only the outer keratin scutes where damaged by either predators or wildfires, but of continuing to survive even where the underlying skeleton (the bony part of the carapace) has been almost totally destroyed. Over the years we have seen a few examples of this. The Testudo hermanni hermanni above that we found in Italy is quite a good example of very extensive tissue regeneration... but it pales almost into insignificance when compared to THIS:
Apologies for the technical quality of this image, but it was sent to us many years ago by someone working with wild Testudo hermanni hermanni as a small print. We sadly also do not have the name of the photographer, but if whoever it was sees this, and contacts us, we would be happy to give them full credits. Despite the low resolution, it is an important image as it shows a tortoise with the entire INTERNAL bony structure of the carapace destroyed by fire, yet, not only is the tortoise alive but a new layer of keratin has developed UNDERNEATH the old, dead bone! This is truly quite remarkable. We did hear of a report of a Stigmochelys pardalis (Leopard tortoise) in South Africa with a similar level of regeneration while we were down there - a park ranger described it to us, but unfortunately we never saw it ourselves and he had no photos. We certainly find his report credible, however.
There are also reports of similar profound carapace regenerations taking place in semi-terrestrial temperate species such as Terrapene carolina carolina (Eastern box turtle)
Finally, here's another example, this time a Testudo nabeulensis (Tunisian tortoise) that we encountered on a field trip.
In this case there is extensive damage to the front of the carapace, with the old, dead bone layer having flaked off leaving regenerated keratin visible below. This can be a very slow process, often taking years... and the animal must be quite vulnerable to predators and potentially to secondary infections, especially in the early phases. That it occurs at all, and that animals DO survive long-term after such traumas is little short of miraculous!
Howey C.A.F., Roosenburg W.M. Effects of prescribed fire on the eastern box turtle (Terrapene carolina carolina) North East. Nat. 2013;20:493–497.