New cat and old cat hiss. Should I separate them for introduction?

I would introduce them slowly to each over the course of about two weeks. I can give you the method I recommend for introducing new cats to each other: Take the new cat, 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 new cat's room while the new 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 new 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 new cat in her room when you go out until they are comfortable with each other.

The best thing you can do is make sure that each cat has their own private space. You may keep each cat confined to their own room with food, water, and litter box for the first couple of weeks. Once they are used to the new home, you can let one cat out so that they can start to smell each other through the door. After a couple of weeks, you can do supervised time together. Pheromones may help with anxiety: https://www.drsfostersmith.com/product/prod_display.cfm?pcatid=40373&cmpid=sc

No, I don't think you've made the the wrong choice. It takes time for a new cat to adjust to the new home, and since she is shy, I would recommend keeping them separated for longer than three days. I will give you a method for introducing them. 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 new cat's room while the new 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 new 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 new cat in her room when you go out until they are comfortable with each other. Best of luck, I hope this helps!

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.

Hi, thanks for using PetCoach! I would be sure that the new and old cat are up to date on vaccines and deworming before coming in to contact. Then I would take the older cat and place her in a separate room or bathroom with a liter box and food and water for 7-14 days. Basically until she seems acclimated. I would purchase a Feliway diffuser, one for the room she is in and one in a location that the new cat can smell it. They can get used to each other by sniffing and hearing each other under the door. After the 7-14 days put the older cat in a cat carrier or use a baby gate at the door so they can see each other and hiss/growl if needed safely. Again for 7-14 days. Then let her out when you are home to supervise. Once that goes well they can be left together alone. You may be surprised out quickly she gets comfortable. I wish you the best! https://www.drsfostersmith.com/product/prod_display.cfm?pcatid=37242

The next step is to rotate rooms daily for at least 2-3 days. This allows the new cat explore the rest of the house while the resident cat spends some time in the new cat's room. This will give your resident cats a chance to smell the new cat and rub their own scent on objects. The cats should be fed in each area with wet food twice daily, and it is also good to play with the cats in each area at least twice daily. The practice of setting up a schedule of feeding treats of wet food, as well as a playtime routine, minimizes anxiety and makes the cats feel more secure. Keep the cats in separate areas for as long as it takes to allow them the chance to become desensitized to the smells and sounds of the cats in the other area. When they all seem particularly relaxed with this process, begin to expose them to the sight of each other. A good way to accomplish this visual introduction is to bring the new cat(s) in a carrier to meet your cats and sniff each other through the carrier wire door. Place the carrier on the floor and allow them to meet this way several times a day for about an hour. Continue these meetings for several days or until they remain calm in each other's presence. If and when the cats are able to stay calm in each other's presence during these meetings, it is time to let the new cat out into the rest of the house for a few minutes. The length of the visits can be increased gradually each day. Depending on the personalities of the cats involved, this process may take a few days or a few months. If it appears that any fighting maybe be close to occurring while you are supervising, put the newcomer back in his/her room and proceed more slowly. If those supervised play times go well, you can begin to allow them to cohabitate in your home. If any aggressive behavior occurs at any time, begin the introduction process again. It is very important to understand that this process can take as little as a few days, to sometimes much longer. It is all dependent on the cats involved. If things don’t go well right away... One of the most important steps to dealing aggressive behavior between cats is to recognize the different types of aggression and understand their underlying causes. A short list and description of some commonly seen aggressive behaviors include: chasing; ambushing; hissing; swatting; and/or biting. If you see these behaviors, seek help from your veterinarian. Most cats get along fine if the introductory process is done correctly. Please seek help from your veterinarian if you feel that things are not progressing well, or if you have other questions.

Hi there and thanks for using Petco Pet Education Center, formerly Petcoach! Congratulations on your new kitty! In these situations it is best to do introductions very slowly. Some suggestions I have for you are as follows: 1) Use a Feliway diffuser to reduce overall tension in household 2) Go back to the beginning and over the first week introduce by smell only (introducing cats to each others bedding or something that has their scent on it) 3) Then introduce by sight only but no direct interaction. Do this for a week 4) Finally introduce cats together but only with direct supervision and with plenty of escape routes for both cats. Only leave them together for a very short time at first 5) Have plenty of tall cat towers and other things for the cats so they can observe each other from a distance 6) Have at least 3 litter boxes in different locations and definitely continue to feed separately and have separate water bowls. I hope this is helpful! Good luck to you and Malish!