My male rat just lost his cage mate recently. He is about a year old, and has been on his own for about a month now. We recently brought home a young male, set up a temporary cage next to our older boy, then today introduced them and things went fine. However, our older boy keeps mounting and humping our new one. He's not drawing blood or seemingly hurting him, but our new boy does seem a little annoyed by it.
Why is this happening? Most of the answers I'm finding online say he's trying to push his dominance and show he's the alpha. I know alpha theory in dogs was debunked a long time ago, and while I know rats aren't dogs, I'm not sure I buy it for them either. I'm willing to hear everyone's opinion though.