Hi everyone I'm not sure if anyone can help me, I'm new to this I used to be on another forum. Basically I have a white Guinea pig he is lovely (it's a boar) I also have another black Guinea pig (also a boar) my white Guinea pig has a black all around his bum area just between the back of his 2 legs? I don't have a clue what it is at all and it doesn't seem to be bothering him at all? I just find it very weird. They live outside and I thought maybe it was dirt at the start but it's been there a while now, it wasn't like it before? Can anyone help me???