There are two major categories of cat aggression – aggression against people and aggression against other cats
Aggression with People
Cats may demonstrate aggression toward people for a couple of reason. One is the they have not been socialized well. If they are afraid of being handles and touched, they may react out of fear but hissing and scratching. When the person backs off the cat learns this behavior works to keep people away. This reinforces the behavior and makes it more likely for the cat to act aggressive in the future.
Related to this is aggression from over stimulation – this is the cat who is sitting on the owner’s lap being petted, and suddenly starts to bite or scratch. At a certain point, the petting becomes an annoyance to the cat, who is saying “stop it!”. Learn how much personal contact your cat can tolerate without getting to the aggression stage.
Cats are predatory animals, and will often take it to an extreme when playing – hiding under furniture or behind doors and then leaping out at people. This is the cat’s predatory and stalking mode. Kittens should be corrected ( a gentle shake holding the scruff of the neck will work – it’s how mother cats tell kittens this action is unacceptable) and given toys to play with to discourage the behavior.
Aggression against other cats:
Territorial aggression – cats are actually more territorial than dogs, and may not tolerate a newcomer into their household or neighborhood. It is not uncommon for an established family cat to tolerate one new cat to the house, but completely dislike another. Cats do not get over territorial aggression or accept the newcomer. Territorial aggression can also develop when a kitten has reached sexual maturity, and is seen as a threat.
Defensive aggression – happens when a cat perceives he can not escape from the attack he perceives is coming. Usually this is a reaction to another cat in the household; an attack may precipitate if the approaching cat does not turn away.
Displaced or redirected aggression – this behavior happens when the animal or person attacked is not the animal who provoked the attack. For example, if a household cat is territorial and sees another cat outside through a window, he may turn around and attack another household cat member, because he can not get outside to the cat provoking the behavior.
KEEP CATS SEPARATED with closed door – let them get used to the idea of each other without being able to see each other or have any physical contact. This is the ideal way to bring in a new cat to the household, and this step may take weeks to work until they accept each other.
DON’T allow fighting to continue between cats; separate them as above. They will not work things our or develop a hierarchy like dogs will.
DON’T try to punish a cat – it will likely make aggression worse.
DO seek veterinary advise to rule out physical problems and seek a referral to an animal behaviorist.