On his Wikipedia page, in the 1966 - 1975 section it says it took a lot of persuasion to get him to use the wheelchair. This suggests that he wasn't in dire need of it at that point. His first child was in 1967, the last in 1979.
6. Extremely high ammonia levels in the water can damage the outer layer of skin and cause shedding. RES are tolerant of high ammonia levels while map turtles are not, so this problem is more likely to occur with Graptemys species.
The simple answer is that snakes shed their skin because they are just like all other animals. All animals shed their skin â even you! In mammals, especially humans, this is an ongoing process that's rarely noticed. Skin shedding in reptiles is different. Instead of an ongoing process, reptiles shed skin periodically.