If you just dump this new rabbit into the established colony, it's probably gonna get shredded - but I guess you know that. The best method I can come up with would be to confine this rabbit in a cage within the colony's space, so they can smell but not touch. Hopefully, they can get used to the presence and the smell of the new rabbit over time, and it won't seem "new" when you finally let them get together. This might work, or it might not - I have had rabbits that lost body parts to a rabbit in the cage next door (toes, chunks of ear, part or all of a tail . . . ). When you do let them get together, I would take the newbie and one of the lowest members of the colony and introduce them in some space that doesn't "belong" to either. If you can get this rabbit to buddy up with some of the colony members in neutral territory, they will be unlikely to kill it when on the colony's home turf. This depends, of course, on just how "alpha" the most dominant rabbits in your colony are - some may be fine with rabbits they already know, but totally ruthless and unaccepting with those they don't.
