Overview | First sight | Neutral territory | Intro - Part 2 | Moving in Together
Unlike America, we don't have to do a 3 week quarantine before introducing our rats, although it is recommended you wait a couple of days to make sure the new rat isn't sick, and doesn't have skin parasites such as mites or lice.
Rats can almost always be introduced to new companions, no matter how old they are, however some intro situations can be easier than others.
The process can take several steps, and can take different amounts of time, depending on how successful each step is. One step might only take a few hours, or it could take several days.
Introducing a baby rat to another baby rat is usually the easiest pairing, while introducing two adult males often takes the most time, especially if they're unneutered. I've had introductions that have gone so smoothly that the new rat is living with the existing clan within a couple of days, and I've havd more problematic introductions that have taken several weeks. With patience and perseverance you can usually succeed.
Rats are however individuals, and sometimes they can take a disliking to a certain rat, and you may find they continually fight and can't live together. This is rare, but can occur, so be prepared to house the rats in separate cages if necessary, permanently. If the problem occurs with males, neutering can often solve this, although it can take up to 8 weeks for the male's behavior to change.
If you're introducing a baby to adults, it's recommended you get two babies. This way they have each other during the introduction process, and they can comfort each other if they're being bullied by the resident rats. I also wouldn't introduce babies to adults until the babies are 6 weeks old, especially when introducing to males rats.
Look for signs of aggression through each step. They'll indicate how well things are going, and give you an idea on whether to continue working on the same step, or whether you can move on to the next. Obvious signs of aggression are huffing and hissing, walking sideways, kicking, and puffing up their fur to make them appear bigger than they are. The little puffballs really do look ridiculous when they do that, so try not to laugh at them.
The first step is to place the cages side by side, so the rats can see and smell each other. Don't place the cages too close to one another, or else they might be able to nip each other through the bars resulting in bitten noses, toes and tails. Also take something from each rat cage and put it in the other cage. This gives them a chance to smell the new rat close up without actually being face to face.
Next switch rats to the others cage for a short time, giving them a chance to explore each others cages and possessions.
Whatever you do, do not put the new rat in the current rat's cage while the current rat is still in there, or vice versa.
The next step is to introduce them on neutral territory. Somewhere that neither rat usually plays. I've found the bathtub works best as it's enclosed. To mask each rat's scent you might want to dab a bit of vanilla essence on each rat. Make sure you have a spray bottle filled with water and towel handy, should you need to break up any fights.
You may observe some squeaking, puffing up of fur, or dominance behavior, such as the resident rat flipping over the newcomer and aggressively grooming it. Don't worry if the rat being groomed is squeaking. This is the rats way of saying "you're the boss". All of this is perfectly normal, so try and let it run its course. Generally if there's no blood, it's ok, however you will want to separate them if serious fights break out, of one of the rats is feeling terrorized. Be very careful when separating fighting rats to make sure you don't get bitten. Throw the towel over the offending rat, and remove the rat using the towel.
You may have to do this step several times, depending on how well it goes. If possible, keep initial introductions short. It is better to end an introduction session on a positive note rather than having to separate upset rats.
If introductions on neutral territory appear to be going well, you can leave them together for several hours to give them more time to get used to one another. Provide food, water, and a blanket or towel to sleep in.
After the neutral territory intros have gone well, it's time to let them interact in an area where the resident rat is used to playing outside of the cage. You may find that the resident rat will be much more aggressive, but this is normal as it's his territory that's being invaded. Once again, watch for signs of aggression, and separate when needed. Feeding them treats is also a good idea, as eating together can be a bonding experience for the rats.
The good news is we're almost there! Now it's time to take the big leap of faith and move them into the same cage. Remove all the objects from the cage that will be the new home, and thoroughly wash and scrub the cage and its accessories so it no longer smells of any rats. Add new bedding to the cage, and return the clean cage accessories to the cage. Place each rat in the clean cage, and watch them very carefully. You will probably observe a fair bit of scuffling and pinning of the newcomer, but don't interrupt. This is perfectly normal. As long as they're not hurting each other, let them work it out.
You may notice a bit of squeaking, dominant grooming, and an occasional squabble over the next few days, as they get used to one another and determine a hierarchy. However it shouldn't take long before they're completely used to one another, and playing, grooming each other, and sleeping together.