getting rats to socialize with each other

Question
I have a Male Res Rat and a Male Hairless Rat and a Female Dumbo.  I want to put the two males in the same cage so they can keep each other company.  If all the rats are out together playing, they act okay.  But when I put the 2 males in the cage, which is a big cage,  they only get along for about 15 minutes, then they fight pretty violently.  I had to remove the hairless rat because he was getting tore up pretty bad.  Is there anything that can be done to make them get along better?

Answer
Hi Jeremy

How long have you had the male rats?  

Also, the reason they fight is because they are fighting over territory. They get along outside the cage because they dont feel that their territory is being invaded but soon as you put them together, they feel the need to defend their turf and prove their alpha status.
How old are they?

Also, what about the female? Does she have a cagemate? She should not be with the males at all unless she is spayed or they are neutered since of course female rats go in heat every 5 days and they are sexually reproductive as young as 5 weeks old.

Let me know about their age and how long you have had them and I will tell you the best way to deal with their aggression. It will work out so dont worry, its just a bit upsetting when they fight!

Sandra