The male must be separated at the first sign of any aggression or dominance on his part if you are keeping them together for more than a few days. This will prevent injury to either rabbit and may even save both rabbits' lives since fights can be very serious with these naturally territorial animals, despite their generally docile nature. When your female's heat cycle approaches - an event that will happen several times each year - you'll notice she becomes extremely affectionate towards her cage-mate, grooming him extensively and wanting to spend all of her time in close contact with him. When this happens, it's definitely time to separate the two rabbits again. The male will start to mount the female, and while this may seem cute to us humans it's actually a very aggressive act on his part and can lead to serious injuries. Separating your rabbits at other times during the year is not absolutely necessary, but it is always a good idea to be aware of their natural behaviors and when fights are more likely to occur. With a little bit of planning, you can successfully keep a male and female rabbit together without any bloodshed.