agression

Question
I used to have 3 rats but one recently passed away and now i have 2 i used to
have them all in one cage but since my sweety passed away my other 2 rats
don't get along at all, i've had to separate them in two different cages because
the won't stop attacking each other and its not just an occasional thing they
were constantly at each others throats i don't understand what happend .. i
was hoping you might have some insight..
thanks :)  

Answer
It seems that the rat that passed away may have been the alpha and now there are two males without a leader. Both may want the role which is causing friction between the two. I have seen this alot with males. Depending on their age, they may not over come this and will have to remain living apart. This is also nothing new to me as I have had many males (intact) that after many months, even a year or more together all of a sudden start to hate each other and have to spend the rest of their lives living in separate cages. Dont feel guilty about it though. They made their choice and usually do very well alone. You can let them out to play and see how they act with one rat in his cage while the other roams the area. Chances are they will fight through the bars though. Keep their cages near each other too so they continue to know each others scent.
How old are they?