introductions of adult male

Question
Hi i hope you will be able to help with this matter as i have read alot of information on intro's but not quite of this nature.  We have a nearly 2year old male rat who we bought at about 5mths old on his own. he was on his own when we got him and wasn't very friendly, however over time he has got used to me and has softened somewhat, though still may bite other people on occasions. The problem is we became aware about 6mths ago that he was a social animal(i hope) and should be kept in a group of same sex animals so started to think about getting him a play mate. He now isn't grooming himself as well as he could, probably due to his age so we could see it was important we sorted it out as soon as was possible, we have now bought a new very big cage and two 11week males.  As our resident rat is so old and has always been alone is it still possible to introduce them? so far both cages are next to each other so they can smell through the bars and he hasn't even bothered to get out of his bed to have a sniff but the other two seemed quite curious.  He spends alot of his time asleep now, but i would love him to be able to do that with the cosyness of a family around him. Any help you could offer on this would be extremely beneficial. Thankyou, Kind regards Alana

Answer
It is possible to introduce them and you did right by getting two babies to play with each other - one by himself probably would annoy your older boy. Introduce them in a neutral area (clean bath tub or table top) and see how they do. If they get along fine, place them in the big cage together and watch very closely. The rule of thumb with rats is NO BLOOD, NO FOUL - but as old as your big boy is, I'd be worried even about tussels. If they seem aggressive at all, separate them and let your older boy live in peace. A show of dominance (standing up, boxing, bruxing loudly, puffy fur) is to be expected, and may take a day or two to pass.

Good luck.