Adding a cat: the right combination in terms of gender and family ties

A lot has been written about introducing a new cat to a resident cat’s home. There are often difficulties because the resident cat’s home is their ‘home range’ (to use wild cat language) and it is being invaded by a hostile outsider. This may lead to aggresssion. All the advice is about slowly introducing the new cat to the resident one but in this post I like to discuss the type of cat in terms of gender and family ties that might make the task easier.

Cuddling cats
Cuddling cats. These two get along through the chemistry of a good relationship. Photo: FreeIMG. net – in the public domain.
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It is probably better to go back a couple of steps and if you’re thinking about a multi-cat home in the future it might be better to adopt two littermates who have been raised together. They may well get on better than average throughout their lives. This is certainly recommended by Jackson Galaxy. It might not be 100% successful. In the wild when cats become independent they travel away from their natal range and find their own home range at which point they compete with each other even if they were littermates. Psychologically the same rules apply to domestic cats. I remember when I adopted my current cat the rescue centre woman was firmly of the opinion that siblings should not be adopted together because they won’t get along. I disagree with that and I think you will find that most other people do as well. But, as mentioned, there’s no guarantee.

Dr Yuki Hattori

The Japanese cat veterinarian and cat behaviourist guru, Dr Yuki Hattori, touches on this subject. He writes that it is important to choose the right combination in terms of gender and family ties. He believes that the pairings that work best are a mother and one of her offspring or two siblings (as mentioned above). They have lived together since birth which must boost the chances of success. If the cats have no blood relationship he advises a neutered male plus female pairing as being the most successful. The next most successful would be two females. Two males are less likely to succeed and they are the most intensely territorial. He advises against an older resident cat having to accept a kitten because of the kitten’s high energy levels may stress the older cat. I think this is a weak argument. I don’t think older cats become particularly stressed by a kitten’s antics.

Two cats getting along nicely
Two cats getting along nicely. Photo in public domain

VCA hospitals – US

VCA Hospitals are a big animal hospital group with lots of veterinarians. They agree with me in saying that there’s not a lot of information about the compatibility of unrelated cats. They do refer to a Swiss study which indicated that an adult resident cat might be more amenable to accepting the introduction of a younger cat, than one of the same age or older. A kitten might be best. This is an interesting thought. Dr Yuki Hattori deals with gender and these veterinarians refer to age. It makes sense to adopt a younger cat as the newcomer because there’d be less of a threat, I would have thought.

The same research study also indicated that if you want to adopt an adult cat, one of the same sex was more likely to be accepted. This goes against Dr Yuki Hattori’s advice. VCA hospitals also advised that two males are more likely to be compatible than two females. This is tenuous advice in my view. Of course the more important factor is individual cat personality. This will override the slight benefits of gender selection.

Love Actually. Two Cats.
Love Actually. Two Cats. Photo in public domain

Anything else?

There is a dearth of information about introducing a new cat to the home in the context of their gender and age. My gut feeling is that adding a much younger cat of the opposite sex is probably the best bet. For a resident male, a young female might be best. Female cats are less territorial than males. For example, in the wild they tend to spray less often. Also, when they become adults they tend to claim a smaller range than male cats. This might indicate that they are less territorial which, in turn, might indicate that female domestic cats are less likely to be less aggressive in protecting territory when push comes to shove. This may translate to being more amenable to being in the home of a resident cat. Another example is tigers. Several females occupy home ranges which are within a single male’s home range. This strongly indicates the natural order is that a female fits in with the intrusion of a male which in turn supports the argument that a male domestic cat will be more accepting of a young female and vice versa. And common sense would indicate that introducing a young cat, even a kitten, will probably improve the chances of success because of lower threat levels.

Black Tabby and Ginger Tabby Cats Together
Black Tabby and Ginger Tabby Cats Together. Photo in public domain.

Caveat: as mentioned these are not guaranteed formulas for success. The personality of the individuals are bigger factors. Adult cats can have the right chemistry like humans which overrides the ancient wild cat attitudes inherited by domestic cats.


There is a need for a backstop and Jackson Galaxy nicely talks about introducing a new cat to the home in this video. Jackson has his own special way of explaining things.

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Useful tag. Click to see the articles: Cat behavior

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