Bunny fighting

Question
We have 2 11-week old male rabbits.  They are supposed to be brothers.  Recently the slightly larger male has been humping the other rabbit, and has twice led to a fight, involving bunny fluff and injuries to the smaller rabbit.  They live together happily in a large cage and run.  What should we do?  

Answer
The males need to be seperated until they are old enough to be neutered (which can be as early as 3 1/2 months, if the testicals have dropped by then, but most vets prefer to wait until 5 months). It sounds like the larger one's hormones have started kicking in, which is causing the problems. The younger one may also be starting to be feeling the affects of hormones.