I have just gotten a new guinea pig today and he seems completely healthy behavior wise, but when I was letting him run around in a pen by himself for a bit I noticed a little black patch right above his butt/lower back area. It seems like a scab and I tried pulling it off and it didn't bother him when I was doing that. I am worried it is a sign of mange but it could also just be a bite from another guinea pig before I got him. He has all of his hair and isn't itching or anything. He had a couple pieces of dandruff but it wasn't noticeable. Has anyone else had this problem? I don't want my other piggies to get sick and I want to make sure that my new one is healthy.