Hey thanks, I think it's marking his territory because he's maturing, and he does it as soon as He is taken out. And refuring to luckies4me's question, when my boyfriend got him, he didnt know he was a male and is under the assumtion that two males will fight, he'd like to get another, but doesnt want babies, or fighting, would another male be alright with him if he is newly introduced now? ALso, if this new rat isn't the same breed/size as his current one, will that cause problems? Thx for all your help