Easiest introductions ever
Recently I ended up coming home (unplanned) with two rescue girls that I couldn't leave behind. I have four very friendly girls already that I needed to do intros with so I do my research and get everything setup for the carrier method.
Things are ready to go so I put them all in the tiny cage and... Nothing. No reaction whats so ever. The new girls look confused as they are quite timid but they accept the approaches. There's some cleaning but nothing two aggressive.
So I decide to move to the next cage and it's exactly the same. They sleep next to each other and sniff each other but overall there's no difference in behaviour.
So I decided to take a risk and jump straight in to the big cage and the only thing that happened was a brief "fight" of who gets to hump the girl in heat. I'm starting to think that my rats are too dumb to notice that two more have appeared.