Introducing A New Cat To An Existing Cat
An assertive cat, for example, may aggressively attack another, seemingly
without cause or warning, often inflicting injury. At the other end of the
spectrum, a previously social cat may seek isolation by camping out under
the bed or in the basement.
Cats may also express their dissatisfaction in more subtle ways: by staring
or stalking another cat, or blocking his access to food, litter boxes and favorite
resting places. The stress can lead cats to mark or have “accidents” outside
the litter box.
Introduce Cats Gradually
Before merging any cats, especially indoor-only with outdoor cats, check
with your veterinarian to make sure all cats are healthy and vaccinations
are current. In some cases, your veterinarian may recommend that cats be
isolated for a few weeks before exposing them to each other.
Once your veterinarian gives the thumbs up, it is recommended to place the
new cat(s) in a room with their own food, water and litter boxes. Keep the
door closed, but allow the unfamiliar cats to sniff and bat at each other under
the door. Swap food bowls and litter boxes every few days to further expose
the cats to the others’ scents.
After a week of separation, place the resident cats in another room, close the
door and then allow the new cat(s) to explore the house and sniff the
The next step is to bring the cats into the same room, but distract and reward
them with the most enticing cat-safe food you can find. Place the more confident
cat in a large carrier at some distance from the other cat(s). The carrier allows
the cats to be exposed to each other visually without the danger of them
physically attacking each other. The more confident cat may be more likely
to be aggressive with the others, so the carrier limits his or her movements. Be
sure to allow all cats to indulge in the food.
If your cats don’t like to be confined, simply separate the cats at opposite ends
of the room while they’re occupied with their food. Repeat this on a daily basis,
gradually increasing their exposure from five to 10 minutes to an hour.
After about a week, or once cats appear to ignore each other, they can be
allowed to mingle a bit. There may still be a little hissing and growling, but
eventually the tension should subside. If aggression between cats persists,
consult your veterinarian or a veterinary behaviorist.
A Few More Words of Advice
1. You can never have too many litter boxes. As a rule of thumb, there should
be one litter box for each cat, plus one more. Since new cats may be unsure
of litter box locations, and others may block their access, the more boxes
you have, the better.
2. Add food and water stations, and climbing areas. Make sure cats have easy
access to food and water, as well as places to climb and observe other cats.
3. Provide escape routes. Offer a safe haven where each cat can make a
getaway from the others. Make sure the location includes food, water, a
litter box and cat toys.
4. Supervise all cat interactions. Until you’re confident that cats are
comfortable with each other, never leave them together when you’re away
from home. Ask your veterinarian about pheromone diffusers and sprays
that can help some cats feel safe and calm. If tension mounts, be prepared
to distract cats and redirect their attention elsewhere.
5. Pair a treat with a distinct sound. Find a treat that each cat really goes for.
Working with each cat in a separate room, make a sound using a bell or
clicker, or just a kissing noise, followed immediately with the treat. Once
the cat is conditioned to look at you when he or she hears the sound, you
can use the sound to distract cats when an altercation seems imminent.
6. Approach aggressive cats with caution. If a fight ensues, do not attempt
to separate cats with your hands, because the aggression could be
redirected at you. Instead, place a large piece of cardboard, pillows or a
blanket between the cats and gently separate them.
Following these tips will help ease the introduction of cats into a household.
While it won't happen overnight—it can take weeks for some cats to adjust to
each other—with a little patience, all your cats may eventually live in harmony
under one roof.