Merging two adult cats

Question
About a year ago my family adopted a female DLH mainecoon mix, spayed from a local shelter. Kittie is approximately 3 yoa and maintains a loving but distant demeanor.  She had never been aggressive.  About a week ago we adopted a male DSH tabby, neutered, approx 1.5 yoa from a foster program. Benny was rated as being good with dogs ad cats.  We started out by keeping Kittie upstairs and Benny downstairs. Over the course of the week we have opened the doors to let each wander closer.  This has been supervised. As expected, Kittie is not thrilled with the new addition and hisses etc. She has not been aggressive and has elected to run back upstairs.  Benny started wandering upstairs a couple of days ago. This evening when the two came in contact upstairs Benny chased Kittie downstairs and proceeded to get very aggressive/attack her. We separated the two and crated them.  Suggestions on how to reintroduce.  Would like to make this succeed if possible -

Dan

Answer
Dan,

It takes 2 weeks to a month (or more for some cats) for things to settle down. As long as there is no blood being shed, major fur flying, or ears pinned back flat then things are going OK. Hisses, slaps, and growls are 'kitty communication' and are normal adjusting behavior. It is never easy or fast introducing new cats. It takes a lot of time, patience, and love. You need to give a lot of attention to each one separate so they know they are not being pushed aside for the other cat, then attention to them together.

Putting the second cat in a cat carrier in the center of a room so the first cat can see and smell the other cat but they can't have direct contact sometimes helps.

You should start off with short visits (perhaps 30 minutes) and lengthen the visit each day.  Your cats will most likely need to establish a hierarchy or pecking order now that there is more than one cat in the house. This is normal and part of the cat way of life.

Interactive play is a good ice-breaker because they focus on the play and not the other cat. Plus they get used to the other cat and gain confidence. The best way is with a pet laser light.

Feeding them together is good too. Not the same bowl, but at the same time. Also feed both cats before the introduction - they'll less territorial on a full stomach. Exchange sleeping blankets too so they get familiar with the other cat's smell.

I hope this helps!