Interferring in rat fights

Question
Hello!

I have 2 female rats, sisters out of the same mother, about a month apart. Pepper is 10 months old, Skye is 9, and I've had them for the last 8 months. The last few months, there have been some dominance fights in the cage, and some of it has gotten pretty vicious. They have absolute opposite personalities, and I think some of the fights are just Pepper saying "Enough is enough!" with Skye.

I adopted 4 boys 4 months ago, they're 6 months old now. All four are brothers, and my plan is to get them neutered soon, and introduce them to the girls, to give Skye some playmates who will play and tussle with her, and give Pepper some quiet company. One of the boys, Tony, started frantic mounting of his brothers last week, and they didn't seem to notice.

This week though, there's been some boxing and chases. I try to ignore most of it (they have to work out the dominance!), but Tony had Bruce cornered, and Bruce was squealing, and Tony was still stalking. I used a bottle of water to mist them, which broke it up while they cleaned themselves, and it seemed to be forgotten.

At what point do you interfere with a rat fight? I know logically they have to work it out, but my brain also says that they're in a cage, and unable to flee like they would in the wild. Any advice would be appreciated!

Answer
Hi Amanda.  There are different schools of thought on this topic, but the majority, including myself, feel that aggression should not be permitted for the sake of safety.  

Your brain is correct.  A cage leaves no room for escape and the submissive rat(s) may end up getting hurt.  Assertive behavior to establish dominance in a group of rats is normal but when it turns aggressive or violent, it should be stopped.  In fact, if you notice signs of imminent aggression (poofy fur, hissing, sidling, etc), you should immediately intervene, wearing thick gloves to avoid injury to yourself.  

If this behavior continues, my advice is to keep the aggressor in a separate cage until they can all be neutered.  Remember that after neutering, it will take several weeks for the male hormones already coursing through their bodies to subside so they will have to be kept apart until their system is stabilized.  You can discuss this with your vet.

Here is some interesting reading material about aggression in rats
http://ratbehavior.org/Aggression.htm

Please let me know if I can answer any other questions, and good luck with all your babies.