New Rat Introductions
Whenever you get a new rat it is a good idea to do a proper introduction. You may not be able to tell how your current rat(s) or new rat(s) will react or take to one another. Injuries or even death could occur if things go wrong.
An introduction is just a way for you to allow two (or more) pets to meet in a safe neutral manner so that you can observe and intervene if needed.
**//NOTE: A proper quarantine should always be done when bringing new rats into your home with your current rats. A proper quarantine should truly be done in a completely separate airspace, so a different home like a friend/family if possible. If this isn't possible at the very least I would suggest as far apart as possible with zero contact between the two. Separate floors/rooms. No handling one after the other. No using items inbetween cages. I suggest a 30 day quarantine, with zero symptoms present. This means if on day 29 if they show symptoms, you restart the time when no symptoms are present again.
The information given here will presume a quarantine was already done. //**
These days as a breeder I rarely if ever do introductions anymore. I know my rats well and know that I breed them to have a sound temperament and no hormonal issues. I also make sure that each baby has had the proper time to learn positive socialization and social group dynamics. And I do change my rat's cages around quite often, so they are constantly meeting new rats. I know my rats very well, I know their individual, as well as genetic/line history and I, am very experienced at reading body language and watching for small problematic signs of an issue brewing.
But for a pet owner, I definitely do suggest always doing a proper introduction between new rats. Your current rats may be absolutely lovely, they may never even bicker with their cage mates but that doesn't always mean they will accept new rats easily or at all.
Don't take the risk. It only takes one second for something really bad to occur and you can never take it back.
I also want to stress that this is true for any pet. Bringing in a new pet can be stressful and it is wise to be careful and take your time, no matter if you have two cats, or dogs or rats, etc...
First, whenever you bring a new rat into the house you should have a second cage available. If you already own rats I will NOT adopt to you without a second cage of some sort. For quarantine ofcourse and just in case something goes wrong and intros do not go well. This can be a smaller/temporary cage. Some smaller cages have wider bar spacing so remember it needs to have 1/2". A bin cage properly made, makes an excellent second cage. And it can be used for travel or cage cleaning or whatever so it isn't a waste.
Now there are many many strategies for doing intros. I am going to first discuss some common ones that I disagree with and why.
1. The carrier method
This is probably one of the most debatable methods. And in my opinion, one of the worst.
In this method, you place your new and old rats together in a small carrier so they don't have much room. The idea is to FORCE them to be in close proximity to one another and bond over this stressful situation.
Why anyone possibly thinks it is a good idea to force them into a stressful situation is beyond me and feels cruel and is definitely unsafe. It is like someone suggesting if my dog & cat do not get along I should lock them together in a dog crate until they either work it out or.... I am sure most sane people are understanding that "or" part and how that will be the most obvious outcome.
The carrier method can "appear" to work super well. If the rats are all ok rats, sure it will be likely ok. But I would argue it is because it wasn't actually needed in the first place! They were not rats who were going to be an issue. A normal introduction would have worked just fine without the risk or added stress.
The carrier method is putting them in a highly stressful situation and stress, even more so since they may already be stressed by coming into a new home, can trigger illness and myco flare-ups.
In these situations, a normal healthy intro would have still worked.
If I want my beloved current pet and my new pet to get along and bond, shouldn't I want to have their meeting be a positive experience?
Animals do not think as we do. They aren't going to understand what is going on. They are just going to take away that this moment and scary, stressful experience is related to this other rat and the carrier as well, which could be a whole other bag of worms!
How about we don't cause undue stress to our pets?
The MAJOR issue I have with it though is if the rats are problematic, aggressive, fearful or already have some issues. A small space will be extremely stressful for them. Either two things will happen- they will appear at that moment fine. This is a survival response. They are unable to protect or defend themselves, the smart thing for them to do is to be calm and wait. It does not magically fix the issue. It tricks you into thinking everything is fine. And later on, there could be serious issues between these rats. Or the rat could attack and a rat could be seriously injured or cause trauma since they weren't able to escape it. Even a less serious fight could cause MAJOR injury because of the small space.
It's like shaking up a can of soda and hoping it doesn't explode all over when you open it. It is risky, stressful and reckless in my opinion. It WILL NOT solve any issues and it doesn't allow you to fully monitor and watch body language.
2. Other methods of "stress bonding"
Such as bathing or doing something to put all the rats in a stressful state to force a bond.
For the same reasons listed above, do not do this. It will merely cover up true behavior and likely make it worse. Again, let's not cause stress to our pets.
3. Placing cages side by side or cage switching over a period of time.
This is also putting your rats into a stressful situation. If they are calm and fine with this, then there is no reason to do it. But let's say they are fearful, aggressive, stressed. all that happens is they continue to be those things with a big scary enemy next to them. This will put them on high alert. All they know is this other rat is invading my space. Imagine a big scary spider (or idk whatever you are afraid of) sitting on the ceiling above your bed at night. You can't reach it and you are laying there wondering if it will fall on you, crawl down, where it went, etc... that feels like torture to me.
I want to say that this method is often used successfully with other species. All animals are different and that is important to remember. Some animal species may not be able to do other methods for their safety.
I also think that this may be a safer method for less severe issues between your rats. But it does pose some serious risk for stress that I do not like.
4. Using food
Sometimes people like to try and cover their rat's scent with food or use it as a distraction. I do not feel this is a great idea either. Some rats may have food aggression issues. Some rats may be very fearful and having another rat push them too fast to get up in their space to lick food off could be very stressful and risky.
The same as above, either it really isn't needed or there is going to be a very scary issue caused by it.
If things are going well for a good while, introducing treats mindfully can be helpful in reinforcing that meeting friends is a good thing. But I would give them some time first to just check each other out without distractions.
All of these methods can go smoothingly fine... but that generally just means they didn't need to be done at all. When you bring up these issues there will ALWAYS be that person who goes "noooo its fine! I did this method and my rats got along and I have no issues now!" Guess what? They didn't need to be introduced that way then. And there are also people who have smoked nearly every day and lived to be over 100 years old and healthy! That doesn't mean smoking is healthy.
The issue comes when the rats DO have an issue and all you will do is cover the problem, make it worse and stress everyone out!
What should you do?
This method of intros is to make every rat comfortable, cause the least amount of stress for all involved and allow you to properly monitor their body language.
Things to keep in mind:
Don't intervene with a hand/body if a fight breaks out. You can be seriously injured. Throwing a towel, spraying with water can help. keeping a small box to put on top of one rat until you can remove the other is good too.
Do intros when you have the time and energy to pay attention without distractions for at least a few hours.
I would suggest keeping children and other pets away during intros. You don't need to overwhelm or distract the animals. keep it peaceful and calm.
Sometimes intros do not go well. Sometimes a rat will just not accept another. If you are concerned do not push it or try to force it. If you feel even a hint of concern, separate them. It is not worth the risk.
Step 1: Clean your rat's cage. Deep Deep clean. You want it to be like brand new. Take it apart, get every little nook sparkling. You also want everything added to the cage to be clean or brand new. This includes food dishes and water bottles.
Step 2: Deep clean around the cage. The floors, the walls, everything. or if possible it is much better to move the cage to a new area just for the first week or two.
The idea behind steps 1 & 2, is to remove any sense of territory or territorial behavior. It is a more neutral space and should help both rats feel more comfortable.
Step 3: Keep the cage slightly empty. This is so if there is a fight they are less likely to be injured on something. Do not place anything inside the cage that has a blocked/dead end. Such as igloos, houses, boxes, beds, etc... you dont want either rat to feel they trapped or cornered.
Step 4: Place two food dishes and water bottles on opposite sides of the cage. Food aggression can be an issue in some rats and you also dont want anyone to not access the food or water.
Step 5: You should introduce them in a neutral space. This space should be secure and hopefully new or not used often with your current rats (and properly cleaned as well). A bed, closed/blocked hallway, secure playpen, or bathtub are good choices.
Sniffing, ignoring each other, grooming one another, sleeping together, popcorning (this is when they bounce around with excitement).
Signs that are generally ok:
I would keep a watchful eye on these behaviors but as long as they do not escalate they are usually acceptable, though not ideal. Small bickering and squeaking, humping, pinning, chasing as long as they separate themselves after.
Puffing of fur, side stepping (this is when the rat turns to its side while still facing the other rat), backing up towards the other rat with their butt first or sideways with the rear first, noises that sound like hissing or growling, kicking, shoving, boxing (rats standing up on box legs and hitting or just facing off), actual fighting, biting, lunging, wounds or blood drawn.
A fight can happen very quickly! And an injury can happen very easily. Do not push them to be together. Let them take their time. If things start to make you uncomfortable, stop, take a break or put an end to it. Your goal is not to let anyone be injured.
If things go great: Yay! I would be fine putting them together in the cage. Still monitor.
If things go ok but you still have some concern: Try again tomorrow or wait a few days to try again.
If things go poorly: Separate right away. Depending on how serious you can either try again in a week or so or if it went very badly, do not try again.
I can not stress this enough!!!
It is ok to go slow. Take your time. Trust your instincts.
If you have multiple rats and they are ok together but one or more are not ok with the new rats, then just keep the new rats and your other rats separate. If you have many rats then you may be able to split into two groups with those who get along.
If one rat is having issues getting along with others, I would first suggest to neuter/spay. It will not always help so do take that into consideration. If it is a male, you could try neutering and keeping him with females.
Having a rat checked out by a vet can be a good idea as well just in case. Many health issues can cause a drastic change in behavior and even aggression or fear.
This is another reason I only ever sell my rats in pairs and highly suggest when bringing home a new rat to bring them in as pairs. Just incase your current rats will not accept the new one, the new one will have a friend still and not be alone.