This website says you can't.

1. Once a group of one male and several females is formed and bred, you cannot introduce any new animals without it being immediately attacked and killed by the original members!
2. Two males can and will likely fight to the death if left together in a group with a small number of females.
3. Never remove the male from the group and try to reintroduce him, even only after a day of separation. The females will kill him upon reintroduction.
http://www.metalmonkeyexotics.com/blog/?page_id=822