So far we have had Mr. Biggelsworth the 8 week old kitten confined in my office at home. He does go to the shop with me during the day. The other three cats know that he is there and one of them - Bob- is not happy at all. I have let the other two (Cleo & Coby) sniff the kitten and they both have just given a gentle hiss, more like a loud breath. I know they will be OK in time. Bob on the other hand is spitting mad. He'll lay outside the door and growl like a dog. It was kind of funny a couple days ago. He was outside the room but had both paws underneath the door, sticking a couple inches into the room. He was growling and the kitten on the other side just watched from about 6 inches away. Once in a while he would touch one of the paws and the growling would intensify.
I let Bob into the room this morning and he slinked around the room growling and hissing at the kitten. Never went closer than a foot away. He sounds very threatening but the his body language is not. Ears are not flat and his tail is not swishing. Now he is sleeping on the printer. The whole time Mr. Biggelsworth just stayed curled up on his blanket and watched him.
It has been so long that we had a tiny kitten like that. The other cats integrated with no problems. Bob was the last one to join the household and he assumed top cat position pretty fast. Is he just postering or do I have to fear for the safety of the kitten? They will not be unsupervised for a long while but eventually they need to get along.