(How) Can I introduce an adult cat into a potentially hostile-feline environment?

We have two cats right now, a very old one and an adult female who’s quite aggressive. She’s nice to people, but has a tendency of abusing our older cat. She’s very needy for attention, which can get very annoying. She’ll have sat on your lap for an hour, hop off, and come back ten minutes later howling as though you’ve ignored her all day.

My Mom has fallen in love with an older cat (10 or so) at the local shelter, and really wants to bring him home. My step-dad and I don’t oppose the idea, so long as we can integrate him into the household

Is this possible? How can we do it? Would any other information help?

Explain the situation to the shelter and tell them you are willing to try it, but if it can’t work out you will need to bring the cat back. Let them know you have their cat’s and your own cats best welfare at heart. Many shelter workers consider the cats they children and want to make sure your heart is in the right place.

Someone I knew who used to post here had done some pet psychology studies relevant to her time volunteering at a shelter. She mentioned that the best way to do this was to try to acclimate the cats to each other through a door. For instance, leave the new cat in a spare room so that they can smell each other and hiss at each other and whatnot through a door before you try to introduce them in person, so to speak.

Unfortunately I don’t know how to tell whether this has worked or not, nor how long one should try it. A neighbor’s kitten was once out in the hallway and I feared her escaping, so I took her in until the neighbor returned. I kept her shut up in the bathroom. On her exit later there was much hissing on both sides.

One of my two cats can’t even stand new furniture. It scares him to death. When I moved I tried to make it as painless as possible on the poor guy but he was still afraid to leave the litterbox for three days. Seriously, the damn cat slept in there he was so terrified. I don’t think he could ever take to a new cat.

Oh, more information: all of the cats have endured a move (7 years ago) with no trauma beyond the shift from outdoor-cathood to indoor-cathood.

The new cat seems docile (a little Eeyore-like, frankly), which is what appeals to my mom. I’m more scared that he’ll be abused by our younger cat, even though he’s twice her size.

I do think that Feliway stuff helped some, when I’ve introduced new cats. Mostly the solution was time - lots and lots of it. I despaired about Stokie and Edison for months, and now they snuggle and lick each other.

Give new cat its own room. After 24 hours in the house, take a dry wash cloth and rub new cat with cloth. Take cloth out to old cat and let old cat smell. Give treats while introducing scent. Rub old cat with cloth to co-mingle scents and introduce scent to new cat. Repeat 2-3 times with same cloth. Let them interact through the door (there will be hissing involved) for 24-48 hrs.

For the first face to face, both cats must be on equal ground. (No holding one cat while on is on the ground, this is the perfect way to inflict damage on yourself.) Use a baby gate and open the door to new cat’s room. Let the cats see each other and give treats for good (non-hissy) behavior. Don’t let old cat in new cat’s room, let new cat out into old cat’s territory. Keep new cat room old cat free until the two are able to get along without issue.

Add at least one litter box to the household. Add a separate feeding area for the new cat so that resources do not become an issue to fight over.

Eliminate catnip for the first couple of days. Catnip can cause aggravate aggressiveness in some cats. Use a water bottle to stop unruly behavior.