ASAP! Is my male guinea pig neuetered? Behavior?

Question
Hello! I have two questions about my male guinea pig. First question,
IS HE NEUTERED? I put him in a cage with a female, and i don't know if hes neutered. I looked up on-line what a neutered guinea pig would look like, and he doesn't have huge testicals like the un-neutered guinea pigs in the pictures. My friend rescued him from a shelter, and she doesn't know if he's neutered or not. Please let me know soon.                 My second question is,
WHAT DOES HIS BEHAVIOR MEAN?
He follows my female guinea pig around the cage a lot and sniffs her butt. Also, at random times, his hair sticks straight up, and he circles around the cage, sometimes he circles around the female. When he does that, he make a purring sound. I have not seen them breed yet, and i dont know if hes neuetered...  Please answer my questions soon! tahnk you soo much!

    -Sarah

Answer
Hi Sarah
A good rule of thumb is that if they were 2 boys they would be fighting and a bit aggressive with each other.The hair sticking up could be the male warning the other male that he is the boss
The circling behaviour you talk about is that of a male showing off to his lady friend saying hey look at me im well fit!