I received two albino rats as a gift on July 1st. They came from petco and was told they were both males. One was obviously male the other wasn’t so obvious but I just trusted they were both males. Now the one in question is gaining weight and is becoming more aggressive, when he was my sweet curious little adventurer. I have a bin already set up in case I need to separate them if he is a pregnant female. My question I guess is, should I separate them? I am worried about separating them if I am wrong and he is just gaining weight, I don’t want to take him from his friend. Any advice appreciated. Just want to do the right thing for them.