Yes, I was recently introducing my therapist to a male ego state I discovered I had and was feeling very strange that I had a male, as I am female and my other parts were female too. He said this was not strange at all and that some people even had animal ego states (and by extension, animal alters). He gave an example that one person he worked with had a cat ego state. So I don't see why you couldn't have a bat. Can you deal with the bat alter in the same way you deal with your other alters? Do you have co-consciousness? Can you "listen" to your bat's thoughts? If your bat likes to hang from things, can you put a safe bar or something in your home to allow it be comfy?