It is always disturbing to observe angry aggression between cats who have been first-rate pals in the past. Two felines will be busy grooming each other one minute, and suddenly next, are locked in a beastly battle. It’s only natural to want to break it up before someone gets seriously hurt, and undeniably, often that intervention is called for. Nevertheless, aggression between housemate felines comes in a number of forms, with related causes; it is hard to completely understand these types of aggressive behavior.
One form of aggression is known as play-fighting. It begins at an early age with littermates, or with non-related kittens living in the same household, and is not confined to kittens. Cats have an in-built instinct for survival, be it in the wild or in a luxurious home, and at a very young age are taught predator-prey conduct by their mothers. One kitten will stalk the other then swoop down his/her unsuspecting victim, and games begin. You will then observe them trade off roles, with the prey chasing his/her previous predator. The "cat and mouse game is a favorite among cats. Play-fighting is typically harmless fun and is the first step in the direction of determining a permanent hierarchy among feline population of your home...
Even neutered cats sporadically show sexual aggression particularly if they were neutered after sexual maturity. It appears that their sexual aggression toward each other borders on what I dominance territorial aggression. Sexual aggression is easy to recognize. The aggressor will bite the nape of the neck of the sufferer -cat and attempt to mount him/her, with the same forceful hip movements seen in male-female mating. Of course, no kittens will come as a result of this.
Territorial aggression can suddenly arise between two comparatively evenly-matched cats, and can occur between male-male, male-female, or female-female. Territorial aggression in the form of fighting is often escorted by urine marking, which helps classify this variety of aggression. The aggressor cat is not of necessity the older cat, nor the one who has been in the household the longest amount of time. He/she will preamble his/her attack with much posturing: ears flattened, back raised, with complementary hissing and growling, then pounce on his/her victim and endeavor to bite him/her on the back of the neck. In many cases, the attacked cat will back down by turning and slowly walking away, and the social hierarchy process will have been established. Other times, the victim will put up a god fight, and a vicious battle may proceed. Do not attempt to physically split up the two battling cats; in the high-heat of emotion, they will not be familiar with you, and severe injury could be the outcome.
An effective method is to toss a large pillow between them. This will divert the aggressor’s attention to the pillow and give the weaker cat a chance to retreat.
Most housemate felines will ultimately resolve their disputes; one will reign as the alpha cat, and the other will be satisfied with his lesser role as beta cat. Once in a while you may be challenged with the quandary of two cats that will never get along, and may have to be lastingly separated. Each situation of territorial infighting comes with its own degrees, and it will take an enormous amount of time and dedication from you to work with the felines to determine a living together in peace bargain.