Cat on Cat Aggression
Some arching of backs, hissing and spitting are to be expected. These behaviors, along with occasional spats, are the cats’ natural ways of renegotiating their relative social positions. But if a real fight breaks out, complete with ear-splitting screams and bodily injuries, it's time to intervene. Also step in if one cat is reduced to a bundle of nerves and hides all the time, overgrooms, stops eating or stops using the litter box.
If trouble breaks out, separate the cats, giving each of them access to all his necessities in a stress-free safe room. Once each feline returns to normal, go through the introduction process again. Before actually letting the cats meet face to face, you may want to add a step, allowing them only to see and smell each other from behind a barrier — for example, a screen door or a gate. This way, there's no risk of injury if one cat reacts aggressively. Continue this until the cats no longer behave antagonistically toward each other.
If one cat waylays the other en route to the food bowl or litter box, he is only mirroring the hunting behavior of a wild feline. A cat learns the paths of his prey, then hides in a convenient spot for an ambush. Most household ambushes involve play, at least on the part of the pouncer. However, if the pouncee isn't in the mood, aggression can result. This is a common problem when a younger cat lives with an older one. It can take a long time (perhaps even longer than their natural life span) for one cat to accept that the other doesn't like to play this way. The victim may become discouraged from eating or using the litter box if the attacks continue. Place food bowls and litter boxes in areas with clear, unobstructed views and remove any items that provide hiding spots for the antagonist.
If all else fails, speak to your vet or a certified applied animal behaviorist for advice on remedying the situation. Sometimes medication can be effective in calming aggression until the cats can adjust to each other. If all these efforts fail and you feel the quality of life of one or both cats is being compromised, you may need to find a new home for one of them.
