We just adopted an 8 month old male cat who is already neudered. He is very sweet and playful with the kids but very aggressive with my other cat. The other cat is a three year old male and very shy. I have been keeping them seperate with short glimpses and interactions with each other. It always ends with the new cat trying to go after the old cat and the old cat running and hiding. The new cat seems to be getting more aggressive and tonight he really fought me to try and get away and chase the old cat. I'm worried that this isn't going to ever work out with the two of them. Any advice?
Hi there! I have two cats (10 and 4) and a dog (7 months). I also worked for a grooming salon for some time and I have been certified to train dogs. In my experience, what you are doing is good. Limit the time they are exposed to one another, but slowly increase that time. Any time that the two cats are together , they MUST be supervised. If you can't supervise them, keep them separated, for now. You don't want the older cat to become traumatized or physically injured. And you don't want the new cat to learn that he can run all over the older cat and that's ok. The 8 month old is an adolescent. Even though he's been neutered, he's rowdy because of his age. He will eventually calm down some as he gets older and that will aid in the two cats at least tolerating each other. Something very important is to always give your older cat attention first when you come home, before you give the new cat attention, or he will only become more shy and will not give the new cat a chance. I always say... he was there first!! Part of the process of introducing a new animal into an environment where there are already animals is just the natural determination of pecking order that especially two cats of the same sex will do. Some of what they do, you have to let happen. You just want to make sure that the cats are safe and aren't hurting one another. Our dog is a Rottweiler/Black Lab mix and he wanted to chase the cats all the time. Although he just wanted to play, the cats thought he was trying to eat them! So, in general, they hate him and won't let him near them without swatting and hissing, however, we have taught him that it's not ok to chase the cats or corner them, so now that he has calmed down some and lets them walk around a little more freely, they will even sleep on the bed at night, when he's there, too. But it's taken 6 months to get this far! So, my advice, is give it time. Slowly let them be together supervised by you and for short periods of time and then increase the exposure. Eventually they will develop their own relationship and will know what to expect of each other. They may not get along, but they will both be able to be comfortable however they determine it to be.
Part of the process of introducing a new animal into an environment where there are already animals is just the natural determination of pecking order that especially two cats of the same sex will do. Some of what they do, you have to let happen. You just want to make sure that the cats are safe and aren't hurting one another. Our dog is a Rottweiler/Black Lab mix and he wanted to chase the cats all the time. Although he just wanted to play, the cats thought he was trying to eat them! So, in general, they hate him and won't let him near them without swatting and hissing, however, we have taught him that it's not ok to chase the cats or corner them, so now that he has calmed down some and lets them walk around a little more freely, they will even sleep on the bed at night, when he's there, too. But it's taken 6 months to get this far! So, my advice, is give it time. Slowly let them be together supervised by you and for short periods of time and then increase the exposure. Eventually they will develop their own relationship and will know what to expect of each other. They may not get along, but they will both be able to be comfortable however they determine it to be. 
