Alison Gerken DVM
Properly introducing cats to a household with existing cats is key to preventing intercat aggression and feline elimination disorders. Misinformation may lead to improper introductions, which may lead to increased fear, anxiety, stress, conflict and panic in the cats in the household and the development of behavior problems. There is about a 50% chance of intercat aggression (fighting) when a new cat is introduced to a home with other cats. You never get a second chance to make a first impression and cats are no different. If your cats show aggressive behavior when introduced, there is a good chance that they will still be showing that behavior a year later. In other words, introduce the kitties correctly using the information below the first time to avoid future aggressive behavior. The length of time required for the cats to successfully integrate may range from days to months; there is no exact formula and progression depends on the individual cats. In one study, over half of the adopters reported that their adopted cat was accepted by their original cat(s) in less than 1 month.
Start ahead of time
- 3 days prior to bringing the new cat home, plug in Feliway diffusers throughout the home, as this pheromone analogue may aid a new cat’s transition to their new space, facilitate exploration and reduce stress.
Introducing the cats
- Your new cat should be confined in a room separate from existing household cats.
- There should be no visual contact between the cats.
- The cats’ scents may be exchanged by swapping items that the cat has interacted with, such as beds or toys, or by rotating the cats into one another’s rooms.
- If the cats remain calm in the presence of the other cat’s odors, then introduction in a controlled environment using principles of desensitization and counterconditioning may be instituted.
- The cats should be introduced at a distance and intensity level at which each cat is aware of one another while remaining non-fearful, non-reactive and non-aggressive.
- The presence of the other cat should be paired with a positive reinforcer such as food, praise, play or pets.
- If food is used as a reinforcer, then a high-value food should be selected.
- When each cat can be calm in the presence of the other fairly close to the visual barrier, visual access between the cats may be permitted by placing a baby gate in the doorway separating the cats and opening the door briefly while the cats are at a distance at which they do not react or exhibit fear. To maintain the necessary distance from the door, each cat should be controlled by a pet parent on a harness and leash or one or both of the cats may be confined in carriers. These tools should be implemented only if the cats have been trained to be comfortable with their use.
- When the cats are given visual access move the food or play farther away so that they can stay comfortable. Then, over days or weeks slowly move them closer to the baby gate that separates them.
- Relaxed behavior in the presence of the other cat should be immediately reinforced with food, praise and/or pets before the door is closed.
- Once the cats remain relaxed in one another’s presence for three consecutive repetitions, then the length of time that the door is opened may be gradually increased. When the cats remain relaxed in the presence of one another for at least two minutes, then you should start feeding the cats on opposite sides of the baby gate.
- As long as the cats remain relaxed in one another’s presence, then you can gradually move the food bowls closer to the gate.
- After the cats eat with relaxed body posture on opposite sides of the gate, then they may be allowed to approach the gate and engage with one another, and as long as they remain relaxed during these interactions, then they may be permitted to engage in short, supervised interactions without a barrier before being separated.
- If any body language consistent with fear, anxiety, stress, conflict or panic, then the interactions should be interrupted, the cats should be separated, and the introduction process should be re-started from the point immediately before the cats showed signs of stress. This may include returning to permanent separation except during introduction sessions.
- Sessions should be kept short, no more than a few minutes at first.