How to Introduce a New Pet Rat
Note that not all rats (whether male or female) will accept a cage mate. If a slow introduction does not improve their relationship or aggression, do not force it. Aggressive rats can cause serious harm if they view another rat as a threat.
Rats make great pocket-sized pets for people of all ages. Rats are social animals and thrive with companions in pairs or groups. This is easy when buying or adopting rats from the same litter that have already bonded. But creating friendships between new rats is not always simple. Rat owners sometimes need to introduce a new rat to an existing rat or group of rats. By following a step-by-step process, rats can be introduced safely and without injury.
1. Quarantine the new rat
You should keep the newly acquired rat in quarantine for one to two weeks to avoid the transfer of disease. Quarantine means keeping the new rat in its own cage in a separate room without contact with other rats. This means washing your hands after handling the new rat before handling other rats. You also should not swap out items from the new rat's cage with anything from the resident rat’s cage. Illness can spread through this sort of contact. If you have many rats, this could result in unexpected and undesired vet bills. Some signs of illness to watch out for include:
- lack of energy
- not eating or drinking
- discharge around nose or eyes
- noisy breathing
- excess sneezing
- excess scratching
During this time, you can still interact with your new rat, but keep an eye on their health. Is your newcomer’s nose wet, or crusted with red discharge? Rat noses are naturally dry, and wetness can be a sign of illness. Rats have sensitive respiratory systems and are prone to respiratory illness. An excess of red mucus around the nose and eyes may be a sign of stress, especially after moving to a new environment. But, red discharge can also signal illness if constantly present. Do not confuse the red mucus with blood, but keep an eye on it all the same.
2. Place the cages side by side
After quarantine, the next step is placing its cage side-by-side with the resident rat cage. The cages should be far enough apart that the rats cannot reach each other. This allows the rats to smell and see each other, becoming accustomed to each other. Sense of smell is a big deal to rats, and is much stronger than their eyesight. Rats have different personal scents, like any other animal. Female rats often “scent-mark” the cage, especially if another rat has urinated there. Sometimes rats will mark you because you smell like another rat!
Did you know that you can help introduce your rats by letting them run around in the other's cage? Letting each rat explore the other's smell helps familiarize the scent and helps them become friends!
How many rats do you have?
The rat cages should spend at least one week next to each other, every hour of every day. The rats need to become used to each other’s scents so the newcomer smells less like an impostor and more familiar. The rats should be curious about each other, sniffing and looking at each other. If one of your rats is showing aggressive behavior or hissing, proceed with caution. The rat may have an aggression toward other rats, and may be less likely to accept another cage mate.
3. Introduce them in neutral territory
A few days after placing their cages together, you can have a play date between your resident and new rats. The first introduction should take place in neutral territory to avoid territorial behavior. Neutral territory is a place where your resident rat or rats do not usually play. A common compromise is the bathtub, but can also be the bed, the couch, or anywhere that the rats do not hang out. The bathtub was the best neutral ground for us, and should be harder for the rats to escape from. When having a first play date, have something soft (like a towel) along the bottom of the tub. Place plenty of tempting treats in the middle for the rats to share. Rats love treats, and eating them together is a great way for them to bond!
There is a method on YouTube called The Glove Rat that helps when introducing new rats. It's great for when one or both rats seem jumpy, nervous or aggressive toward the other. In the video, a woman follows the rats around with a gloved hand while keeping close watch on their behavior. The goal is to deflect negative confrontation between the two rats, such as biting. If you get the sense that the rats are going to get into a fight, you place your gloved hand between them and break it up. The glove is there for your own protection, and makes the process feel less nerve-wracking.
See the Glove Rat in Action!
It is normal for rats to express dominance by pinning, grooming, or or chasing each other around. The submissive rat will let out little “eeps” that sound like whispers, and mean that they "give up. Understand that this is normal rat behavior. Dominance is a big deal in rat colonies, and even rats sharing a cage will have scuffles over dominance. Watch out if a rat squeaks very loud or “screams” in pain, or if the rats are taking fighting to a level you don’t like. Some signs of rat aggression include:
- pulling a rat's hair out
- biting and drawing blood
- swinging it's tail around
- hissing at other rats
Watch the play date and follow your gut. If you think one of the rats is taking it too far, separate them. And the first few play dates should be short. Fifteen minutes is enough for the first few days, and you can introduce them as many times as you prefer each day. As the days pass, the rats should know each other more and be less nervous. If you have an aggressive rat on your hands, give them some space before you try again.
4. Introduce them in familiar territory
Once your rats are making progress, you can introduce them in familiar territory. Familiar territory is a place where the resident rat likes to play on occasion. This is different because your resident rats will feel territorial about their location. This place can be the bed, the sofa, or anywhere your resident rat might consider their own. The interactions between the rats here can be more tense than in neutral territory. Having keen eyes and using a gloved hand are very important in familiar territory. Your resident rat may feel the need to guard their territory, and more dominance fights may occur. Watch that neither rat is aggressive toward the other. If behavior escalates to a violent level (or if you feel the need to separate them), end the session. You can always give it another try later.
If play dates in the resident rat’s territory aren't going well, have the sessions on neutral ground again. You can repeat this until you feel that the rats can move up to familiar territory. Do this as many times as you deem necessary. Depending on your rats and their personalities, this step can be simple or take several tries.
Need a new rat cage?
5. House your rats in the same cage
When your rats have bonded enough to share a cage, you can do one of two things. You can house the rats in a brand new cage, or move them into one of the cages either rat has been living in. Moving the rats into a preexisting cage involves a lot of cleaning, rearranging, and time. Save this step for a day when you plan on being home so you can watch the rats. And if you do it in the morning when your rats are sleepy, it can ease the process.
For this step, I cleared off the bed and let the rats play while I cleaned. I had a towel, play tube, toys and treats on-hand to keep them occupied. I decided to house both rats in Patches' cage. I had to clean her smell out and make it seem new and unfamiliar.
You’ll need to clean the cage from top to bottom, throwing out all the old bedding and food. Use a pet cage cleaner from the store that both cleans and deodorizes the cage, and be as thorough as possible. After wiping down the cage and any other objects inside, rearrange everything. If you have a multilevel cage, move the shelves around. Change where the food and water are located, as well as any detachable ledges or other objects. If you have hammocks like my rats do, wash them and re-position them. The cage needs to look new to both the resident rat and the newcomer. It cannot smell like the resident rat, or they will defend it like it is their territory. It helps to disorient the resident rat by adding new toys and accessories to the cage that neither rat has seen. Once this is all done, you can let the rats explore.
As with the play dates, expect more dominance scuffles started by either rat. If the process has gone well, the rats will eventually become good friends. The struggle for dominance will always be present, as one rat will always seek to be dominant. Wrestling and boxing are ways that rats like to play, so don’t worry unless you spot injuries or if a rat vocalizes pain. Remember: in the end it comes down to your gut. If you feel the rats aren't being friendly, then they may need more time apart. The truth is, most rats enjoy companionship and can become best friends over time.
Questions & Answers
My two-year-old rat had to be put to sleep. Now his littermate looks lost on his own. How long should I wait to get him a friend? Also, all the rats I can find are twelve-weeks-old. Is this too much of an age gap?
I've never introduced a baby to an older rat until today and didn't do my homework. I just put a six-week-old baby in the cage with my older one-year-old female. They are both females, and my older rat is very aggressive, and I don't own a second cage. Do I just keep a close eye on them, or do I go purchase a cage and do the introduction the long way?