Why is my older cat hissing at the new kitten after getting along?

IT can be common for two cats to get along sometimes and not other just like children. The cats are working together to figure out perfect harmony in there environment. I would not be concerned unless you notice abnormal urination/defecation or you feel like the two cats are constantly fighting. IF they are having occasional disagreements that can just be normal pet behavior. If you feel the younger cat has a lot of energy I would recommend trying to increase play by hiding toys and treats around the house. Hope that helps

As long as Oliver is fully vaccinated, it would be fine to let them interact with supervision. The kitten is likely hissing out of instinct and won't necessarily attack Oliver. Usually the cats work out their differences in their own way, but you should be there in case they start acting aggressively towards each other. If they are starting to swipe at each other, then it would be best to give them a little more time separated before letting them interact again. Below is a link to an article with some good advice for introducing the two. https://www.petcoach.co/article/5-steps-to-introducing-your-cat-to-a-new-feline/ I hope that helps and all is well with Oliver and the new kitten.

While it's fine that they growl and hiss at each other, as they are letting this new cat know they don't appreciate his presence on their territory, you don't want it to escalate into aggression and one of your cats get injured. I would keep an eye on their interactions as best you can, and step in if it appears that anyone is going to get aggressive.

It may take time for Lilly to accept your other cat even though she is the smaller new cat. Some cats just don't do well together so if this behavior continues or gets worse I would recommend either talking to a veterinary behaviorist (if there is one in your area) or considering finding someone who can provide Lilly a great life as an only cat. Thank you for using Petco Pet Education Center, formerly Petcoach.

It does take time for the existing cat to get used to a new addition to the house, and I recommend introducing them slowly to each other. Take the kitten, 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 kitten's room while the kitten 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 kitten 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 kitten in her room when you go out until they are comfortable with each other.

This is not uncommon with kittens that are not socialized well at a young age. The hissing is more of a reflex than anything and will decrease with time. The best thing to do is spend as much time with him as possible and try to handle him as much as possible. He may act like he doesn't like it at first, but he will get better with time. In most cases they stop hissing and become more normal within two weeks. If it's taking longer than two weeks, then it's best to ask the people at the shelter for some help, or another pet professional. I hope that helps and all goes well with Ollie.

Well, Smickle IS king of the house! Actually just let him hiss away. Eventually the hissing will stop. This can take a good few weeks. Some day they will sleep on the same bed, but when they see you, will hiss anyway. Give him as much love as you used to, and make extra time for cat number two. Not every cat learns to love another cat, however almost all cats can learn to live in the same household. So Smickle is jealous now, but if you can manage to put lots of lovings on him, he will forgive you for bringing in another kitty, into his kingdom, and eventually the two will likely get along. It will take time and you cannot force it.