Hello, I was just at the Toledo Zoo and I noticed one of the female northern white-cheeked gibbons was missing the fur on her scalp, which I’m not going to lie, concerned me a little bit. Why may this be? Is it a sign of sterotypic behavior, namely her pulling her fur out because of stress? Is it likely an indicator of some kind of medical procedure that required the fur to be removed? Or perhaps a sign of aging? I would like to know