New Clients Receive 10% Off First Visit - Get Coupon Now »


Adding a New Cat to Your Household

Posted In: Behavior & Training, Feline Health & Wellness

Adding a new pet to your household can be an exciting time, and there are many benefits to adding a pet to a single pet household. The pets will have a playmate when you may be away at work or school, the extra play may help to keep each of them at a healthy weight through exercise, playtime mentally stimulates pets, and having a companion around can increase a pet’s confidence in the home, decreasing stress and increasing their quality of life.

Adopting a new family member can also be challenging, especially in the instance of introducing a new feline friend to an existing cat in the home. This article will explore why some cats react the way they do to new cats, and some of the ways we, as responsible pet owners, can reduce stress and try to acclimate both pets to living together. It should be noted that not all cats are the same and, while these methods can work to alleviate friction between house cats, there are instances and individuals not suited to multicat life.

Cat Behavior
There is a lot of stigma surrounding feline behavior that markets cats as solitary, individualistic animals with little need for social interaction. Whereas this may be true of the African wildcat, from which domestic cats are believed to have descended, we observe much different behaviors in house cats. The truth is that, though cats may seem more independent than their canine counterparts, most house cats are more than willing to display affection towards their two and four-legged housemates. This willingness depends on a variety of factors.   

The socialization period for kittens occurs between 2-7 (sometimes up to 10) weeks of age. During this period, kittens should be able to play with other kittens to learn feline social behavior. Specifically, this is when kittens learn bite inhibition, the ability to moderate the strength of their bite, as they play fight with their littermates. The American Animal Hospital Association (AAHA) warns that kittens should not be removed from their litter until they are 8-10 weeks of age in order to build healthy social manners. If you have a cat who did not experience social learning within their litter during this time-period, you may find introducing a new cat to your household more difficult, or even unattainable.

Cats do not become socially mature until 3-4 years of age, at which point owners may notice new aggression between individuals who previously got along just fine. This form of aggression is spurred on by the socially mature individual’s desire to lay claim to resources. Indoor cats are known to battle, not only for food and water, but access to litter boxes, perches, windows, toys, and even human attention. It is important to provide enough of these resources that each cat has access to one while the other cat is occupying another.

In a feral environment, domestic cats are observed to form colonies of related adult females and their young. Queens (unaltered females) will co-raise kittens and share in resources when they are plentiful. Tomcats (unaltered males) maintain territory that often overlaps that of the female colonies, but tend to lead more solitary lives. Male cats tend to claim much more territory than female cats. In one study, researchers found that male cats maintain territory three times larger on average than female cats. For this reason, it can be slightly easier to introduce female cats to other female cats, or to introduce one female and one male. Neutered males, especially male cats neutered prior to sexual maturity (4 to 6 months of age), may not exhibit the same territorial tendencies as intact male cats, and thus may be easier to integrate into a household.

In the interest of your pet’s health, and in the interest of battling the overpopulation of unwanted animals in shelters, AAHA, the American Veterinary Medical Association (AVMA), and the Humane Society of Missouri (HSMO) support the surgical sterilization of cats and dogs.

Recognizing Aggression
Studies suggest that there are two types of aggression presented by cats: passive and active. Both displays of aggression seem to be linked to the territorial nature of domestic cats. Active aggression is easy for most people to recognize. Active aggressive behaviors include hissing, swiping, biting, stalking, wrestling, growling, and piloerection (bristling of hair, often along neck, spine, and tail). Passive aggression may be harder to spot. Most people don’t notice it until one cat starts hiding more often or flees when the other cat is present. Passive aggressive cats only have to stare in the direction of the other cat to get their way, and can sometimes have more frequent marking behaviors such as rubbing their faces on surfaces in the house and, unfortunately, urinating on walls and furniture.

Ways to Avoid Aggression
Slow and careful introduction is the best way to go when bringing a new cat into your household. If you don’t have the space to facilitate this, then it may be worth reconsidering adding a cat to your single-cat home. The small chance that tossing both cats into the same space and letting them work it out will work is not worth the risk of injury to them or to you. The following are tools and tricks you can use to help facilitate the integration of a new cat into your home. These are methods that worked when I introduced a new cat into my single-cat household.

Give the new cat its own room. For a week or two, allow your new pet to acclimate to a smaller, less scary environment without the possibility of hostile interaction with your existing pets. Though being adopted and going home is a good kind of stress, moving into a new place with a new routine is still a stressful endeavor for a new pet. Provide ample resources in this room: a litter box, food and water, places to perch, and places to hide. Give them time to adjust, as well as a chance to have quiet, peaceful interactions with you and other human residents in the house.

Use a Feliway® MultiCat Diffuser. The Feliway® MultiCat Diffuser set (sold at all AMCMA locations, as well as at many pet supply stores) is a device similar to a plug-in air freshener that diffuses synthetic pheromones into the air. The pheromones have a calming effect on cats as they mimic the natural signals put out by a nursing mother cat to her kittens after birth. It is believed to give cats a sense of home and security when within a 700 square foot radius, depending on household floorplan. Plug it into an outlet at “cat-height” and make sure it is not obstructed by furniture or corners. It is meant to be placed in the room where cats spend the most time and can help to take the edge off the anxiety either cat may be feeling in regards to each other. Each diffuser refill lasts for 30 days. It should be noted that if both cats are feeling anxious or aggressive, and they will be living in separate rooms for a time, you may need to place a diffuser in each room so that both cats can benefit from the Feliway® product. Try not to put it next to the litterbox, as it can cause some confusion for your pet and inappropriate elimination outside of the box.

Since I only had an issue with my one pre-existing aggressor, and my second cat adjusted very quickly to his new home, I placed my diffuser in the outlet just outside of my new cat’s room so that it was close enough to be present for any interaction my first cat might have with her new housemate through the closed door.

Use food as a positive reinforcement. For two weeks, I fed each cat canned food (a special treat around my house) at the same time on either side of the door. I started each cat about a foot away from the door and gradually moved the bowls until they were touching the door over the course of the two weeks. Both cats gradually came to associate positive rewards with the smell of each other through the crack in the door. Now they won’t eat their canned food apart from one another. Remember that any treat you offer to reinforce good behavior is still calories to be accounted for in your pet’s diet!

Switch rooms. For a few hours a day during the acclimation period, have your first cat hang out in the second cat’s room. This gives your new cat a chance to explore the rest of the house and your first cat a chance to acclimate to the smell of your new cat. Once both cats realize that nothing scary happens when the scent of the other cat is around, it can trigger a real turning point in the acclimation process. This is assuming everyone has the same health status (no respiratory infections, no parasites, similar FeLeuk/FIV statuses). If one cat is sick, keep them separated and get them treated per a veterinarian’s recommendations.

Use a baby gate for supervised interactions. During the third week of acclimation for my cats, I placed a pet playpen in the doorway and allowed the cats supervised interaction through the gate. When I wasn’t around, I closed the door again to keep everyone safe, just in case. I continued feeding canned food on either side of the gate twice a day to encourage them to eat while they could see each other. Neither of my cats are food aggressive, so this worked for us, but food aggressive pets may not benefit from this.

During the fourth week I allowed both cats into the same living space only while I was home. At night and while I was away, the new cat stayed in his own room. Once I was sure that neither cat was going to pick a fight, they started living together full time and have been inseparable ever since.

About the Author
Kelsey Kelly is a clinic assistant at the Animal Medical Center of Mid-America. She has a B.S. in Animal Science from the University of Missouri and has a passion for scientific research, animal welfare, and animal health. She is also mom to two awesome cats - Landon ad Yayoi.

Herron, M. E., & Buffington, C. A. T. (2010). Environmental Enrichment for Indoor Cats. Compendium (Yardley, PA), 32(12), E4.

Martin, D., BS, RVT, CPDT. (n.d.). Feline Development, Social Behavior & Communication. Retrieved from,%20SOC.pdf

Overall, K. L., PhD. (n.d.). Protocol for Cats with Intercat Aggression. Retrieved July 31, 2017, from

The Animal Medical Center of Mid-America has veterinarians at two locations that can answer questions about your pet’s health. Call 314-951-1534 or click here to request an appointment online.