Nothing is more frustrating or inexplicable to the owner than when a perfectly litter-trained rabbit suddenly begins to eliminate outside his litter boxes. Fortunately, the reason for this behavior can usually be tracked down and the rabbit re-trained.
The first thing to determine is whether there is a medical reason for this behavior. Is the rabbit dribbling rather than leaving puddles? This may be caused by bladder infection. Check the urine. Is it pinkish rather than the common reddish pigment? If so, take the rabbit to the veterinarian. Is the urine creamy-looking with sludge, that is, a grainy deposit, in the urine? If so, the problem may be that the rabbit is receiving too much calcium in its diet and is developing a condition that can lead to stones in the urinary tract. This condition may often cause a rabbit to urinate outside his box. If it feces the rabbit is leaving where he did not used to leave it, check it also. Is it unusually soft or runny, or does it have blood or mucous in it? If it is either of these you should take the rabbit to a veterinarian immediately. Diarrhea may occur as a result of a diet change, bad diet, or a disease.
If you can see no signs of a medical problem, it is time to look for another reason for its behavior. Did he get frightened while in its litter box one day? Rabbits sometimes avoid returning to places where they received a fright. If this is the case you may need to relocate the litter box. Have you moved the rabbit's litter box, his cage, or other things in the room? Rabbits, being the creatures of habit that they are, usually hate to have their things moved, and may show disapproval by urinating and/or leaving feces outside the box. Have you brought something new to the room?
Sometimes rabbits decide they want their litter box moved to a different place. Or want a different litter box, for example, a larger one with lower sides.
Another reason for eliminating outside its usual places can be a change in the amount of attention you are giving your rabbit. Have you reduced the amount of time you play with your rabbit? Giving him extra attention may solve the problem. Do you have a new pet or a new person living in your home? Your rabbit may feel threatened or feel it necessary to make it clear who was there first and is top rabbit. Giving your rabbit extra attention and reassuring him that his place in your affections has not changed may help.
Perhaps the most frustrating situation is when none of the above applies and your rabbit has simply decided to take your top rabbit spot over. A rabbit attempting to do this may urinate someplace your scent is especially strong - on your favorite chair or sofa or, worse, your bed or pillow. In this case you need to show you are keeping your spot as top rabbit. Clap your hands when he gets on the piece of furniture. If it does not get off its own accord, lift him and put him onto the floor. You need to make it clear it is your piece of furniture. If it is your bed where he decided to make his move, keeping the bedroom off-limits may work best.