Dear Your Own Vet’s Animal behaviorist,
We have three cats. Two are brothers and the other we adopted separately. The two brothers have been hissing and growling at each other recently. We believe this may have been triggered by the sight or scent of a female cat outside. All three are strictly indoor cats. They have limited access to a screened in patio. What can we do to stop these indoor cats fighting?
This is not the first time this has happened. We are afraid one cat could kill or seriously injure the other.
It is very difficult with indoor cats who see, smell or hear other cats outside. This can cause stress between themselves. The outside cat might be a female, but it possibly could be a male and as the males can’t get to that cat to fight it off, they are now fighting each other.
If you do see a cat outside, then chase it away and try to see how it got in and block that access if possible.
I would suggest that you get some Feliway from your vet and spray this around your house where the cats spend most of their time. This pheromone helps to calm cats down and is fairly successful. You can also try putting a calming collar (same pheromone) on the cats.
If they are still fighting, I would suggest that you contact a good behaviourist who will come to you house and work through the problem with you.