I have recently noticed that my tortoise has these white markings on his shell. I think they have always been there but I am not sure if they are just scratches or shell rot. Please help.
The white you're seeing is bone. The top layer of keratin has chipped away. Its not a new injury and isn't causing the tortoise any discomfort. Years from now, new keratin will cover this spot, but it takes a very long time. Actually the new keratin grows UNDER this white you're seeing and eventually the white chips off. Its really pretty amazing when you think about it.