I have a female cat who is about ten. She has been fixed, and yet suddenly, (since Matthew left) she seems to be "marking" or scenting her territory like a male un-neutered cat. I cannot even begin to understand what is going on. At first I thought she was peeing on something - but the more I have investigated it - the more I realize she is literally marking her territory. It is worse when I open the windows, as she is primarily an indoor cat. Have you guys ever experienced this?