Introducing new rats


Senior Member - Vegan for the animals
Jul 21, 2007
central New Brunswick Canada
Usually people quarantine new rats for 2 weeks if they are unable to do a proper quarantine.
A proper quarantine lasts at least 4 weeks in a different air supply (different building), and quarantine procedures are followed.
You may want to read up on quarantines and also the thread about the importance of a proper quarantine in the reference section.
It is important to be aware of precautions to take and what the risks are if you do not take them.
If a new rat comes from a trusted source such as a shelter or rescue or has been in a home where it was basically quarantined, many people take a calculated risk and do not quarantine once the new rat has been found to be healthy and parasite free.
(Things to consider when getting new rats

If all rats are under 12 weeks of age, then they are babies and you can just put them together.
Babies see other rats as new playmates.

If any rats are over 12 weeks old, then gradual introduction steps need to be followed to ensure that no one is hurt or killed.
Rats over 12 weeks of age view unfamiliar rats as potential threats and it is normal for them to be territorial.

Baby rats need to be at least 8 weeks old (10 weeks is safer) before being physically introduced to a rat over 12 weeks of age.
This is so the babies will be old enough to defend themselves.
Also, young baby rats do not smell like rats and unfamiliar rats will mistake them for prey.
Introductions are easier if they are done before babies are 12 weeks old.

1. To get ratties used to one another put the cages near each other but far enough apart that rats can not reach one another.
Dirty cloths can be exchanged from one cage to another. so the rats get used to each other's scent.
Some people put rats in one another's cages when the occupant is not home to get used to the smells etc.
Other people, however, think that putting rats in one another's cages is not a good idea, that it doesn't help, and that it may even make some rats more aggressive.
This step is usually done over a one or two week period, however, sometimes it takes much longer or goes much faster, depending on the rats.

2. When they are no longer showing signs of aggression toward the unfamiliar rat(s), then intros are done in a neutral territory.
Some people do this on a table top but I found that my rats would leap off the table in fear.
I would suggest you put the plug in the tub, put a fleece blanket in the bottom of the tub and add a dish of yummy food that can not be carried away. That way they will need to gather around the dish in order to enjoy their treat.
Then add all the older rats to all the new rats as a group in the neutral area, and watch.
(There is a step that can occur prior to putting them together in a neutral area if this first step is too big a step for them.)

3. When all the rats have been able to be together in a neutral place for 20 to 30 minutes without any signs of aggression
on several different occasions, you repeat this in a non neutral area such as the play area.

4. When rats have been together several times in a non neutral area for 20 to 30 minutes without any sign of aggression, they are ready to live together.
You take the large cage they will live in and completely wash it out so it doesn't smell like anyone.
You rearrange the items in the cage as well.
You don't want ratties thinking they need to defend their territory.
You put in a plate of yummy food.
(Some people suggest having the cage empty except for a plate with yummy food and gradually adding items over the next few hours.)
Sit back and keep an eye on them for the next 8 to 12 hours or so.

Each step usually takes a week, but with some rats it can go much faster.
With other rats it can take much longer.
There is another step for rats that are very aggressive toward one another but it is not normally needed.

Some people keep a towel handy to throw over the rats in case a fight starts, in order to break it up so the rats can be safely removed.
Others risk being bitten accidently by just reaching in and grabbing a rat to break up a fight.
Watch body language carefully so rats can be separated before a fight occurs.

If at any stage ratties show signs of aggression (puffiness, snorting, backing their rear end or their side
into other rattie, etc) then you go back a step as they were not ready yet.
A bit of aggression is normal and they will pin and power groom but there should be no blood.

Some rats are too aggressive and need to be neutered before they can be successfully introduced to other rats.
So if a rat seems impossible to intro, don't give up. They may need more time, a break from intros for awhile, a new approach, or a neuter.

Some very experienced rat owners modify these steps based on the rats and their extensive knowledge and experience (ie 10+ years of introducing hundreds of rats).
Most people find it safest to stick to these steps and let the reactions of their rats determine the speed at
which they progress through the steps.

(I did not make up these steps. I learned them from experienced rat owners years ago when I was new to rats.
And don't worry if you are afraid or intimidated by intros, everyone is, no matter how experienced they are)

EDIT: In the real world rats have space to back off when they are afraid instead of feeling defensive and fighting. I now intro rats in a large neutral space on the couch where they have space to move away from one another …… I sit on the couch, in the middle and will scoop up and cuddle a rat if they look afraid or start looking puffy. Rats will also climb into my lap for reassurance or safety. I also provide a pillow a frightened rat can hide under until feeling brave enough to venture out to nibble a treat. I am now also using treats that rats can carry away, such as kumut puffs or organic pumpkin seeds …. this allows rats to have a treat and move with their treat to a more comfortable distance. This method may be more dangerous for the pet owner as you might get accidentally bitten, and you need to be aware of your rats and their body language to a greater extent then the other method. It also takes longer then the bathtub method because it progresses at their speed

Good Luck

and for more info on intros see:

*** Also see important information on regarding introducing rats
and on ratguide
Last edited:


May 11, 2019
New Zealand
Great write up thanks.
I'm getting two new boys to add to my current three next week and I am soooooo nervous to do intros.
Will post photos of all my boys when I get them, as I've been on here a bit without introducing my boys.
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Well-Known Member
Jan 2, 2020
New york
Soo i i apparently was VERY quick with introduction. Maybe just because i know my boys and they like new friends.
I think i did all of that in the span of two days. They got on just fine so far and its coming on 23 hours they've been together. My newb even let me hold him today (granted, it was for like .3 seconds)


Oct 10, 2019
Ottawa, Canada
These steps are so helpful. Particularly the note about matching the pace of your individual rats. Each individual is different. We were cautious with our oldest, when we adopted her at 3, since she was known for being aggressive to cagemates... but she has shown absolutely 0 aggression since we adopted her and set her up with new rats. We think she just didn't like that particular cagemate (her sister).

The very first time I introduced rats, it was ridiculously easy. I was nervous, but the rats (two 2-year-old females and the 3-year-old female) bonded near instantaneously and stuck together like velcro from almost day one until the younger two passed away (integrated into the same cage successfully in 1 week). We still have the older girl, who is now 4.

She's been successfully introduced to 3 other rats - two babies, who were 4-months old at the time, and a 1-year-old neutered male. The two baby girls idolized her from the beginning, so were another easy intro (about 1 week)... the male took about 2 weeks before he succumbed to the reality that he would not be alpha in this cage, and now enjoys his role with the trio of much smaller females.

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