Rabbits may bite when they are frightened, experience hormonal fluctuations, crave attention or try to defend something they are protecting. A rabbit is protective of itself and can extend that instinct to its belongings, such as toys, food and its cage.
The Rabbit House suggests visiting a vet when a rabbit is biting to rule out health problems and explore the option of having the rabbit spayed or neutered. Because rabbits are vulnerable prey animals, they can become defensive when they are in pain or feeling unwell. Vision or hearing impairment can also be an issue. Rabbits that are easily startled because their senses are compromised can be prone to lashing out, and rabbits that have blue or red eyes are especially vulnerable to developing blindness and other vision problems.
The Rabbit House goes on to explain that hormones are the most common cause of rabbit aggression. Hormones drive rabbits to fight over resources and territory. They also encourage rabbits to protect their den, or cage, from invaders. This is especially true of female rabbits. Spaying or neutering can make a huge difference in rabbit behavior by removing these troublesome hormones, according to both Rabbit Haven and the Rabbit House.