Cat aggressive after neutering: Will my cats be friends again?

I would wait a few days before panicking about long-term effects. The stress of being hospitalized, the after-effects of anesthesia, and any medications can cause temporary behavior changes. If the cats weren't prescribed pain medications, then I would talk to your vet about that.

Thank you for submitting your question regarding your cats. This can be common after a trip to the veterinarian. The kitten will be covered in different smells. This can cause stress in the older cat resulting in her to act out in aggression. Keep them separate unless they are fully supervised. They should be fine with each other in a few days. In the meantime, you can try a pheromone diffuser to help calm them. Feliway is a good brand. I hope this information helps!

Neutering male cats is one of the most effective ways of limiting inter-cat aggression. There are no guarantees, but castration is definitely the first and best thing worth trying. If you are worried about the two cats hurting one another, I would keep them separated for the time being. Even after the castration there will still be some residual hormones left in the body for a short while. I would consider keeping the two separated for at least a week or two post-operatively before reintroduction. Hope this makes sense.

You should have him checked, or rechecked, by your veterinarian. Neutering typically does not result in more aggressive behavior. Additionally, any sudden behavioral change can be due to illness or injury. Once medical causes have been ruled out, you can focus on behavioral issues. Consider a pheromone product, such as Feliway Spray or plug in diffusers, to help decrease anxiety or aggression. Provide additional litterboxes, bowls, toys and bedding to prevent resource protection. You may have to separate them for a week or two then gradually reintroduce them while employing the measures described above.

It can take several weeks for testosterone levels to decrease after neutering. Until then, consider using a pheromone product, such as Feliway spray or plug in diffuser, to decrease any anxiety or aggression in the home. Provide extra litter boxes, bowls, toys and bedding to prevent food aggression or resource protection.

It could be that she smells differently now that she had kittens, and Homer views her as a stranger. There is a method you can use to help them get along again. I would separate the cats, and slowly reintroduce them to each other. Take Homer aggressive, and put him in his own room with his own food, water, and litter box. Keep the door closed, and for a few days, feed them both treats on other side of door so they associate each other's smell with a good experience. Then let the other cat in Homer's room while he is in a cat carrier. They can smell each other, but not be in contact. If either becomes upset or show signs of aggression, remove the second cat from the room, and try again later. Praise them when they interact appropriately. When they are interacting well with each other through the carrier, you can let Homer out of his room, and see how he interacts with the other cat. Praise them when they interact appropriately, and separate them with any sign of aggression or upset. I would get a cat tree with lots of shelves to give the cats vertical space to get away from each other. I would keep Homer in his room when you go out until they are comfortable with each other.

Thanks for using Petco Pet Education Center, formerly Petcoach! On the whole, I’m not worried about this yet. It can take a couple weeks to feel completely normal after a neuter, especially in adult males. If you have pain medication still, go ahead and give it as even mild pain can cause some cats to be a little crankier than usual. Sometimes, a long trip to the vet or anesthesia seems to disturb cat relations and anxiety is more of a problem. If this behavior is not improving with pain medication, or persists for another week or more, consider these anxiety-reducing home helps. -Feliway- calming cat pheromone- comes in many forms from pet stores or online. 

- Adding a litter box. Studies show that the ideal number of litter boxes for a home is #of cats +1 . This is regardless of how clean you keep his current litter box.

 -making sure he has plenty of “high space”. The safest (and therefore least anxiety-inducing) place for a cat is up. If you don’t already, get a cat tree or put up a shelf or two that he can go perch on. Best wishes to you and Gus!