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Is there any hope of modifying aggressive territorial behavior once a cat has begun exhibiting it? I have two Abyssinian cats: a neutered male and a spayed female, ages 4 and 5, respectively. They are half brother and sister and have been wonderfully companionable for many years, though the older female has always been the "boss." Recently the female has become increasingly more aggressive toward the male and suddenly, last week, she became totally aggressive: stalking, chasing then attacking him. I am deeply attached to both cats but dividing my open-area house into 2 separate living spaces would be difficult and very expensive. I am now keeping the cats separate except when I have the female on a harness. I can stop her from attacking the male, but she is still exhibiting aggressive behavior and I'm afraid if her aggression is thwarted she may redirect the behavior. All 3 of us are traumatized by the situation. Is there any way I can modify the female's behavior and so keep both cats?


I am assuming they are both altered and are indoor only cats.

When this kind of sudden behavior change takes place, it is usually a medical issue. I would have the two of them into the vet for a check up. If a cat is feeling some discomfort, it is not unusual for it to exhibit defensive behavior (e.g. hissing & spitting at the sight of another cat). You could also have hormone levels checked and thyroid levels checked.

There are some cats who seem to go off for no apparent reason and the symptoms get worse and worse.  Our vet calls these aggressive psycho kitties and whatever is going on causes them such extreme frightening behavior, euthanasia may be the best option, but is still a very last resort!

There can be behavioral causes like a change in the number or types of family members, e.g. a new baby or a new pet, but you did not mention it.  Sometimes, just seeing a new cat in the vicinity outside a window, may be enough to cause some of this behavior. If you think it is behavioral, you can check:

look up aggression and behavior issues.  Jackson is an excellent feline behaviorist and has excellent video tapes to demonstrate his suggestions.

Please let me know how you make out.

Concerned regards... Norm.


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Norman Auspitz


I can answer most non-veterinary questions about cats. My particular expertise is pedigree cats, breeding and showing. However, I am versed in feline behavior, cat breeds and their characteristics, general feline husbandry, and the like.


I judged for the Canadian Cat Association from 1975 until 1982. I am currently an approved allbreed judge for the Cat Fanciers'' Association (the world''s largets cat registry), and have been judging for them since 1991. I have been breeding pedigreed cats since 1971 and have been exhibiting pedigreed cats in shows since 1970. I obtained my first pedigreed cat in 1970 and have never looked back. In 1971, I obtained my first Abyssinian which has become my primary breed. In addition, I have bred Manx and Persians. Currently, besides the Abyssinians, I am also breeding Maine Coons.

Cat Fanciers'' Association, inc. (CFA) and the Manx, Maine Coon, and Abyssinian breed councils. I am currently Abyssinian breed council secretary.

Cat Fancy Magazine, The Abyssinian Chapter in The Cat Fanciers'' Association Complete Cat Book, and Articles for various editions of The Cat Fanciers'' Association Yearbook

I received a B.S. from Drexel University in 1968, a M.Math from University of Waterloo, in 1970, a Ph.D. from University of Waterloo in 1975, and a MBA from McMaster University in 1980. I received my approved allbreed judging status in the Cat Fanciers'' Association in 1999.

Awards and Honors
We have produced a number of Cat Fanciers'' Association (CFA) National winning Abyssinian and Maine Coons. We have produced a number of Abyssinian and Maine Coon Distinguished Merit females (an award for a top producing cat), including the first Distinguished Merit Abyssinian in the red (sorrel) color. I am the CFA Abyssinian breed council secretary and belong and/or hold office in a number of cat clubs. I am also a member of the CFA Judges Association.

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