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Successfully Introducing Cats – 50 Ways to Keep Them Lovers (Not Fighters)

Introducing cats

A veterinarian’s guide to introducing cats. Where most people fail in introducing cats is allowing them together physically too soon. When introducing cats to one another, SLOW is most vital component to success in the long term relationship for the cats over their very long lives. Plan in terms of 2-4 weeks (or more) apart for a proper introduction of adults cats as a rule, not hours or days. Some cats will move along this process more quickly, and some may take even longer. Kittens are usually much quicker to warm up to other cats.

In the end, there is no magic proper time frame that works every time. The individual cats should be your guide. They should only be brought together physically when ALL cats are no longer agitated or upset while meeting at a safe barrier. If any of the involved cats are still hissing, spitting, growling, slapping or looking agitated then the time is not right to bring them together physically! Wait until the cat’s curiosity kicks in. Once ALL cats involved are calm and beginning to show curious interest in one another – then the time is right to move onward in the introduction process.

These instructions also work nicely for re-introducing cats that are fighting with one another. All the same principles apply and can be used in that situation as well.

Step 1: Plan for Introducing Cats

Many a cat or kitten has been brought home on a well meaning whim. But you really should recall a few important things about cats. One is – they do not live naturally in giant cooperative communes as a rule. They tend to be isolated hunters that live at most in small family groups. It is not terribly natural for them to seek out strange cats for non-breeding purposes after they are adults. They keep and defend their territory with their staked out resources very vehemently and effectively in the wild. The point is – it is not a terribly natural or realistic expectation to ask a number of older adult cats to live together peacefully.

Next there is a lack of socialization issue that comes into play when introducing cats to one another. Kittens in general are taken away and isolated in one house, with maybe one other kitten or cat and then STOP being routinely introduced to other new cats ever. They miss the LONG socialization period they would have had with other cats out in the wide world as kittens.

Almost no one advocates that cats be socialized to meet and greet new people or new cats during this primary socialization period. They can be, just like puppies can. They should be, but they are not. This means suddenly deciding to get a new cat is hard and stressful for cats the older and more isolated they have been for long periods of time. The point is – be aware it is stressful and not all fun and games for every individual when introducing cats to one another.

Some cats are loners and will NEVER adjust to new cats. Some cats can tolerate 2-3 other cats but have their limits for any more than that in their space and in their face all the time. Know your individual cat and keep THEIR happiness in mind when planning on introducing cats new to the mix. Just because you want 15 cats does not mean the 2 cats you have now are down with that plan. Please recall to be respectful of the individual animals’ needs that you have chosen to care for and keep them in mind.

So plan for the cats and with the cats in mind. Have the area prepared, have all the info and physical stuff in hand to help minimize stress for them. And be patient and mindful of your resident cats’ personalities and needs and your ability to cater to the needs of ALL the cats you choose to share space with. The more animals you have, the greater the time needed to manage their husbandry needs AND to look after their mental and environmental enrichment needs. EVERY single new animal you add to your home WILL change the group interaction dynamics, every single time.

Be mindful of these factors and plan rather than reflexively react with only your heart and not enough thought. Remember the happiness of all the creatures involved in YOUR split decision when introducing cats to a stable existing household.

Step 2: Separation is Key When Introducing Cats

Ideally you can bring in the new cat and let them have a room to themselves – a spare bedroom or bathroom that can be equipped with their own resources (food, water, litterbox and toys). Smaller is better at first. You do not want a brand new cat to have too much spare space to careen around. They just need a nice space to chill out in and decompress from the stress of their move to a new home. To begin with it is fine for them to only be able to smell one another beneath the door.

The resident cats should remain with their usual free roam of their territory while introducing cats into the home. The goal on their behalf is to stress them as little as possible while they get adjusted to the idea of a new cat in ‘their’ space. So business as usual for the resident guys and gals is the name of the game in the beginning. Aim for the least disruption in their lives as possible while they are allowed plenty of time to adjust to the new addition.

So what about less than ideal? If you do not have a spare room to devote to one cat for awhile, then arrange for a very large dog crate. The bigger the better. It must be large enough to allow for all the cat’s resources (food, water, litter, toys, bedding). Make sure if it is a wire crate (rather than a solid sided airline type crate) that initially all but the front area has been covered with a thick blanket so that the confined cat cannot be attacked physically while taking refuge. Alternatively set up the new cat’s crate in a corner of a room so that two sides are completely protected against sneak attacks by resident cats.

At first cover the rest except the front gate including the top. ‘From on high’ is a superior offensive and defensive position for a predator species, so don’t put the new addition at a disadvantage that way. When using a crate, make sure the only way the resident cats can approach the new cat is on equal ground and only a small area at the front that the confined cat can easily withdraw away from. More of the crate can be uncovered over time, but I always keep one half covered so the confined cat has a ‘safe space’ to retreat to at all times.

Can you do it other ways? Sure. Sometimes it might be better for the new cat to have free roam and an older cat that is less active to be the one confined when introducing cats. Younger cats have higher energy spend needs, both mental and physical so in those cases it might work better that way. You can always switch things up if they are not working, just be slow, and keep them separated until they prove to be interested in rather than aggravated by one another’s existence!

Step 3: Encourage Positive Associations

When introducing cats, I wait to start this step until they have ceased excessive fussing at the barrier. Once any major agitated protesting has calmed down at the barrier then I begin scent swapping. Cats are every bit as scent oriented as dogs and we tend to forget that. It is important to remember it when introducing cats.

How do you scent swap? Switch out bedding (or towels they have been laying in a bed) from one cat’s room to the other and vice versa. That lets them explore the scent of one another more closely without fighting and get more used to the other cat’s presence and scent in their territory. All without any fighting. You can gently smooth each cat with a soft cloth or dry wash rag while you are interacting with them and then leave those in the opposite rooms to be sniffed. Do it freshly each day, and for the resident cats, try leaving the ‘new cat scent’ in different rooms in ‘their’ house area. Not much more than that at first.

Once that is going well, then move to a physical barrier that they can see and scent one another through. While introducing cats, they should not be able to touch or physically slap one another through the barrier. So, for example, open the door and add a tall baby gate that is firmly affixed to the door frame and mounted all the way down to the floor to prevent cats from going under. Then add a temporary mounted screen curtain (Magic mesh or Magnetic Screen door) behind the baby gate to prevent the cats from going over the top of the gate.  Fix up whatever works for your set up and level of handy DIYness.

The see through barrier allows them to clearly see one another, get close and sniff one another. However, they are still unable to fight or do any physical harm to one another! This is important when introducing cats, because they have memories like elephants for bad experiences. It takes a loooong time for some cats to give up the grudge caused by an initial fight or two if serious enough! This method allows them to verbally express their displeasure with one another (hiss, spit and growl to their heart’s content) but prevents any physical fights from breaking out. Cats get over name calling (hiss and growl) much much easier than they get over serious physical brawling.

The next step in introducing cats properly is to increase the positive interactions near the barrier and increase the scent swapping. After they get over any hostility from being able to see one another then start feeding and/or treating them with extremely favored high value treats (such as tuna, canned mackerel, sardines, cooked chicken) within sight of one another on each side of the barrier.

Figure out whatever the magic ‘tolerated’ safe distance is that they will cooperate with and still eat the awesome provided treat and start at that distance. Gradually then move the food/treats closer and closer to the barrier. If they stop eating and start fussing then back up to the last tolerated distance and go slower coming together near the barrier. Feed each day at the barrier. Treats at the barrier. Play with each cat on its side of the barrier in site of the other cat. Build a healthy ‘bank’ of positive associations in being near one another is an important part of introducing cats successfully.

Step 4: Increase Scent and Territory Swapping

While the see-through barrier is set up, and they seem to be getting along better, then you begin to further scent and territory swap. Keep an eye out at this stage of introducing cats because they can clue you in to how difficult it might be for them to share things in the future. Close observation during this period of introducing cats can also give you an idea of which resources may be problematic. That will allow you to plan accordingly ahead of them physically coming together!

So other things you can do now – start swapping them into one another’s areas. The confined cat gets free roam of the house to explore for awhile. The resident cats get to go walk around in the new cat’s isolation room. This can also help keep the more restricted space cat from getting overly bored as well. You can clean up the litter boxes and swap them out as well. Ideally you get extra boxes so each cat has two, and just switch one box. That way each cat keeps its own box and has access to sniff and explore the scent of the other ‘stranger’s’ box.

When introducing cats, also use this time to figure out the favorite treats and toys/games for the new cat and your resident cats if you do not already know. It will be important to use every positive reinforcement tool at your disposal moving forward. Consider teaching ALL the cats during this time a positive interrupter cue. It may come in really handy when they are learning to get along together out of isolation!

Keep this up until ALL involved cats are no longer hissing/growling, etc. There should NOT be physical together time when introducing cats until ALL of them are over their aggravation/agitations and their curiosity kicks in. When all cats seem interested, then begin allowing them together for short periods of very attentively supervised time. If that goes well without a physical spat 3-4 times then gradually allowed more time together until the barrier no longer seems necessary. If they fight seriously = back to separation again. Do not go forward in your process of introducing cats if one cat in a multi-cat household is still not happy! WAIT for ALL cats to be in curious, interested in moving forward mode.

Step 5: Plan for communal living harmony when introducing cats

While they are isolated is the time to plan on how to help them all get along safely and happily. When introducing cats you want to set them up for success! You need to have a good understanding of common stress points in multiple cat household in order to plan for success when introducing cats.

Cats most commonly stress (or fuss/fight) over access to resources. If you are a predator then control of resources can mean the difference in life and death, the difference in thriving and merely surviving. What are resources? The things they need: food, water, territory (the best nap spot), preferred people, attention, toys, etc.  They also get stressed if one cat is too predatory with their play style, and predatory cats learn quickly how to stalk bottleneck areas in order to assault other cats in the household. Bottle necks are easy for a bully cat to exert control over as well. Bottlenecks in pathways to needed resources are BAD for communal harmony.

While in the process of introducing cats, you need to carefully ponder the layout of resources in your house. Make certain that there is ALWAYS more than one type of resource available in more than one area of the house. For instance: having five litter boxes is not helpful if they are all side by side in one room at the end of a long narrow hall.  That equals only ONE litter box, not five!  Three feeding bowls in one room upstairs does not count as 3 feeding stations = that only equals one feeding station in cat math.

Bully cats do not always fight and leap on other cats in the house, but instead they just stand there quietly and stare. One bully cat can sit ‘benignly’ at the hall entrance or bottom of the stairs and successfully block access to the resources at the other end. A predatory play cat can hide and leap out to ambush the cats approaching such areas as well.  Bottlenecks are bad for harmony!

When preparing for introducing cats, be aware that multiple cat households should plan to have one box per cat plus one as a MINIMUM.  Multiple cat households should prepare to scoop all litterboxes clean once daily as a MINIMUM to maintain communal harmony for all the cats.

Make sure that one cat cannot cover access routes to every food bowl, for example. Look at your house and think like a cat trying to be king of the <resource> and make it impossible for all of whatever <resource> to be body blocked at once by a single cat. Remove the bottlenecks by increasing the resource stations available!

The next part of alleviating stress in a multi-cat household is watching the general pathways in the house and the provided resting places. Do all cats have different areas where they can get up high away from one another? If not they should if possible. All the high roosts and hiding cubbies should not all be in the same room. 

Look at each room like a cat that is stalking prey. Can the ‘prey’ get out of each room in more than one way?  If the only way through a room is right through the open middle then that is likely to be a problem for the shy cats and a major fun hunting ground for the predatory ones. Make learning about the more subtle feline body language tells a priority to help you recognize who is stalking and threatening whom. Check out our links for feline body language resources here.

Can you arrange an ‘elevated highway’ through the room so there is not just the wide open middle to cross? Try adding a cat condo here, and a couch there for them to walk across the top of, or add some wall walkways.  Can you adjust a couch placement so they can go behind the couch to traverse the room?  Sometimes simple things can help prevent problems down the road.

Finally, keep energy levels in mind in different aged cats as well as pain thresholds if you have an elderly cat. Adult cats do not always appreciate a kitten assaulting them for play everrrrry single time they move or try to go eat, drink, or use the bathroom.  Make sure that YOU are providing adequate enriching play time for the kitten or new young cat that YOU wanted!! The older adult cat did not ask for the new addition after all, nor did they sign up to be the baby sitter and occupier. You did! 😉

Final Tips to Consider When Introducing Cats

Other things that can set you up for success: Remember “tincture of time” and use more of it liberally because it is absolutely the main ingredient for success in introducing cats. Give the separation period enough time to work its magic! Time is what allows the cat’s curiosity to get the better of it and be used to your advantage in introducing cats.

Pheromone diffusers (Feliway or Comfort Zone) will assist, so will the use of the pheromone sprays right around the barrier area. Purina makes a probiotic (Calming Care) that may help and can be sprinkled over dry or canned food with really nice acceptance by the cats. Neither will be miraculous on their own, but used in concert with a proper introduction plan they tend to help well. Other over the counter choices to help with stress (again, assist does not equal a magic cure all):

  1. Feliway or Comfort Zone Diffusers – good for a room
  2. Feliway or Comfort Zone Sprays – good for use at specific areas like by a separation barrier
  3. Purina Calming Care Probiotic – accepted readily by most cats sprinkled over their food.
  4. Vetriscience Composure treats for cats
  5. Zylkene for cats
  6. CBD – not particularly effective thus far in my experience with truly stressed cats.

Increasing mental engagement and environmental enrichment ALWAYS helps both the resident cat(s) and the new cat to adjust better. When introducing new cats to the household, give them ALL plenty of other things to think about and look forward to other than harassing one another! Make a commitment to spending 4-6 weeks at least working actively on increasing the cats’ enrichment regularly to help. If you cannot do that…. then you need to honestly re-evaluate whether you can and should commit to bringing home a new cat or kitten! Please look at our article on Feline enrichment ideas here to help you when introducing cats to one another.

While you work on introducing cats, be aware that sometimes the “really social cats” that are so very enthusiastic to meet the ‘new’ cat are often a bit too bully/pushy and/or a touch too predatory in their approach as far as other cats are concerned. What you see as happy and eager to meet, the other cat involved may interpret as rude and stressful. So watch for that, and if one cat is super exuberant and aggressively plays – then enrich the heck out of them and help the other cat catch a break while introducing cats.

Once they have graduated from separation to living together, remember that it is perfectly fine to offer a slightly stressed cat some time on its own for each day going forward. Make them a place they can go with all the needed resources so they can decompress and escape stress and harassment. A few hours of defined break from one another daily can go a long way to helping slowly de-stress their interactions when together and build better long term relationships when introducing cats successfully to one another.

This should help you provide your new cat the best chance to integrate into your house. Enjoy your new addition! – Dr. May