Cat suddenly aggressive after brother returned home? What to do?

Oh no, that's not good! I would separate the cats, and slowly reintroduce them to each other. Take the cat who is aggressive, and put her in her own room with her 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 the aggressive cat's room while the aggressive cat 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 the aggressive cat out of her room, and see how she 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 the cat in her room when you go out until they are comfortable with each other.

Oh no, that's not good! I would separate the cats, and slowly reintroduce them to each other. Take the cat who is aggressive, and put her in her own room with her 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 the aggressive cat's room while the aggressive cat 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 the aggressive cat out of her room, and see how she 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 the cat in her room when you go out until they are comfortable with each other. I hope this helps!

I agree! What you may be seeing is redirected aggression. The angry cat couldn't get to the source of its anger (the outside animal), so it projected it onto the other cat. I would separate the cats, and slowly reintroduce them to each other. Take the cat who is aggressive, and put her in her own room with her 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 the aggressive cat's room while the aggressive cat 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 the aggressive cat out of her room, and see how she 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 the cat in her room when you go out until they are comfortable with each other. I hope this helps!

I'm sorry you are having such problems with your cat! Bringing a new cat home can be stressful for him, and that would be why he's reacting to poorly. To Ginger, there are now intruders in his home, but I can give you a method that may help improve things in your home. I would separate the cats, and slowly reintroduce them to each other. Take Ginger, 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 Ginger'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 Ginger 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 Ginger in his room when you go out until they are comfortable with each other.

If the female is being treated for lymphoma, she will be smelling differently when she returns home from treatment, and Mochi will see her as a stranger, leading to the aggression. I would separate the cats, and slowly reintroduce them to each other. Take the cat who is 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 the aggressive cat's room while the aggressive cat 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 the aggressive cat 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 the cat in his room when you go out until they are comfortable with each other. I hope this helps!

Hi and thanks for posting on Petco Pet Education Center, formerly Petcoach! If Milo has stayed for the week with your brother or sisters cats whom Milo has never met before while you were away, it possible those cats did not like Milo very much or became stressed with a new cat in their home. If Milo use to get along with your brother/sister's cat before, perhaps you leaving triggered the stress and aggression of the other cats. Cats do not do well with change and can really become stressed when their owner's habits or environment changes suddenly. It is best is Milo is kept at distance from your brother and sister's cats as much as possible for several weeks and then try slowly reintroducing them with a few short introduction sessions under supervision. Feliway pheromone spray diffusers around the house can work on easing tension. I hope this helps and best of luck to you and Milo!

Oh dear, how stressful! Unfortunately it can be common for cats to lash out when one cat in the household suddenly smells or acts different - as they tend to do when they come home from the vet. Most of the time they go back to their normal interactions once the strange smell (in this case, from the vet clinic) wears off and the cat relaxes and acts like herself....but in your case, there's nowhere for Tribble to hide and isolate herself while she readjusts to being home. The most important thing right now is to not allow them to fight or have negative interactions. As long as they can be kept separate while they both settle down, they will probably do ok - but if they continue hissing and growing, and worse yet if it escalates into a fight, that could permanently damage their relationship. I would absolutely keep them separate until they seem to be relaxing. I understand that'll be challenging in a 1 BR living space - but if possible, you could put 1 in the bathroom with her own litterbox & food, and then have them switch places tomorrow so they can get reacquainted with each other's smells. If that's not possible, you may need to crate them both while you work on their reintroduction. Perhaps you could borrow dog kennels so they can each have their own living space while they're confined. I know this isn't an easy answer - but the most important immediate intervention is to do what you need to do, to keep them from fighting while the stress levels come down! Finally, adding a pheromone diffuser such as Feliway Multicat may help promote a calming atmosphere. I hope this helps!