Sudden change in behaviour towards his brother

Question
I am hoping you can help me, I have two 18month old domestic males, they were hand-reared as kittens, because there mother didn't want them, they were the only two  of the litter to survive, and so came as a pair to prevent more stress. They have always been really close, always sleeping together, washing each other, and even staying together when they go out. One of them has just been in the vets for 5days as he had a serious stomach infection. While he was gone the other cat cried constantly, would not leave me alone, and needed constant attention which I was only too happy to give. His brother returned home from the vets yesterday, and since then I have been pulling my hair out! The cat already at home went mental hissing spitting and growling, I was totally shocked as he had really missed him, it also scared me, he has never been aggressive, the cat that came back from the vets didn't understand, he didn't react to the aggression, he just ran away, and hid. I really don't know what to do, I am keeping them apart because I am so freighted of him hurting my cat that has just come out of hospital, is this normal behavior, please help me!

Answer
Hi Sarah,

This sometimes happens when one cat is taken to the vet. What happens is the one who went picks up a bunch of strange odors and his brother doesn't recognize them. The brother who was left home see's his brother but smells another. It is confusing him and he is attacking him because of this.

You are going to have to reintroduce the vet one into the house again. Keep them separate like you are. Take bedding from each other and switch it. Rub a towel on one then the other. Or rub one on yourself and then rub them. They need a common scent. Gradually let them see each other again. If the hissing starts remove them and try again later. It will take a little time but they will get back to where they were.

You can also get a product called Feliway. This mimics happy cat pheromones. It acts as a kitty tranquilizer. Use this while you are reintroducing them.

When you have to go to the vet next time take both of them with you. This will prevent anymore episodes of this. Good luck.

Ciao, Karen