Rats are very social and are happiest in pairs or groups of same sex or neutered rats. A single rat needs lots of daily human attention. Rats can be kept in groups of up to six Females per cage and four Males per cage (PROVIDED THE CAGES ARE BIG ENOUGH). They should be able to stretch on their hind legs in their cage and they should be able to climb (which comes very naturally to them)
Good sound advice with compliments of Liezel from Moonstones rattery www.moonstonesrattery.bravehost.com
“Integration with older males should be done very slowly and gradually. I have a very Alpha male at the moment who is housed on his own – he is extremely hormonal, over scent-marks everything, rubs his sides and feet on everything continuously, and when put with other ratties fights and draws blood (not just normal scuffles) I tried to put him with one of his 6 week old sons – but he attacked the little one also. This rat is just overly hormonal – neutering him will cure this. Remember that from 6-8 months males go through a very hormonal stage and they might fight to sort out a new pecking order in the cage. Very few rats get so agressive (like the one I have now) Best way to integrate 2 new males is to put vanilla essence on them, and introduce them in a neutral place – like in a room where neither of them have been before.
Also set up a NEUTRAL cage and let them get to know each other there – never put a male rat in another male rats cage and expect them to get along.
When my 8 new males arrived I had them all in the same cage so I could observe who got on and who didnt (they all arrived in the same crate anyway) And then separated them into 2 groups, and these never fight – with the exception of our overly hormonal Blue!
So yes one needs to be careful with male rats when introducing a new male, especially if one or both of them are mature. It is rare for them to hurt a baby, but it can happen. Remember babies are sexually mature from 6 weeks!”