In spite of their cute and cuddly appearance, bunnies are capable of aggressive behaviour too. Such behaviour is usually defensive in nature because the rabbit feels afraid or territorial. It also shows up when the rabbit is sexually frustrated. Rabbits often become less aggressive once they have been spayed or neutered.
Nipping and biting
The most obvious sign of aggression, nipping and biting, come in various degrees of severity. Rabbits feeling threatened or annoyed may nip another rabbit or a hand. This is just a warning to "back off." If the rabbit is feeling cornered or territorial, the nip may escalate into a full-on bite that draws blood.
Another obvious sign of aggression is when the rabbit lunges at some offending object. When a rabbit lunges, it's saying that it wants to be left alone. Continuing to interfere with it might result in a nip.
Stance and Tail
Rabbit tails are usually held tightly against their bodies. A tail held stiffly up and away from the body indicates the rabbit is tense about something. It is usually accompanied by a rigid body stance with front legs held apart instead of close together. This body language indicates the rabbit is preparing for a lunge.
Taking lungeing a step further, some rabbits may run at another rabbit, a person's feet, or at a hand reaching into its cage. Rabbits typically engage in this behaviour if they feel their territory or "personal space" is being threatened.
A rabbit's ears are the most expressive part of its body, and they offer many clues about the animal's mood. When a rabbit is happy and relaxed, it usually holds its ears up and pointed forwards. As the rabbit becomes increasingly annoyed, it will rotate its ears sideways, then backwards. A sure sign of a troubled rabbit is one with its ears pointed backwards and held flat against the body.
Growls and Thumping
Rabbits are not very vocal creatures, but angry rabbits will make noises that sound like short growls or grunts. Rabbits also thump their hind legs as a means of warning those around them of potential danger. However, thumping can also be a sign that the rabbit is annoyed and ready to jump at something.