There could be a number of reasons why a rabbit bites...frombeing suddenly startled and reacting out of fear, to some underlyinghealth issue, to hormones, to cage aggression. If you've ruled out anyhealth issues with your rabbit, and if this behavior begins to be moreroutine than out-of-the-ordinary, then you might want to consider thata) either your rabbit has hit puberty, so to speak, and is goingthrough a (hopefully) temporary phase, or b) your rabbit is becomingcage aggressive. If hormones are the issue and your guy isn't neutered,then that might be an option you would want to consider - if so, find arabbit-savvy vet who can weigh all the issues (pros and cons, risks ofsurgery vs. benefits of neutering) and assist you in making a decision.(Another thing to consider is that if he is housed with a companion, hecould be displaying dominance and protectiveness toward hispartner...again an issue that might be dealt with by neutering, if heis still intact. )
If you determine that your rabbit is cage aggressive, then you willneed to handle him carefully whenever he is in his cage. When you (oranyone else) needs to put their hand in the cage, approach quietly, butmake sure he is aware of your presence...startling a dozing bunny cancause a nip or bite. Wear a light pair of gloves if you feelhe might deliver a nasty bite. Place one hand on top of the rabbit'shead and gently hold his head down - covering his eyes - whilst puttingfood in the cage (or taking dishes out...whatever the reason is thatthe cage needs to be accessed) to keep him from being able to see thehand or react to it. Talk to him in a quiet loving tone while doingthis, and praise and reward him afterward. Even better, if you need todo things like fill food and water dishes or change bedding, remove therabbit while doing so, and put him back in once you're finished. Don'trearrange anything in the cage if possible...always leave the litterpan in it's place, food dishes in their place, etc. Praising him andgiving him a treat after you've put him back might help to win hisconfidence.
Rabbits can become quite territorial about their living quarters...itis, after all, their private sanctuary; the one place where they feelsafest from any predators or threats. And to a rabbit, a hand comingtoward them - even a familiar one - can be interpreted as a threat ifthey are territorial. Not all rabbits develop this, but for those whodo, some can be taught through patience and training to stop biting,while others don't catch on. For those who don't, they willneed to be treated a bit more carefully when handling them around thecage.
