Introducing Rats

Never put a new rat in with your resident rats without using a safe method of introduction. It is important to take your time when introducing rats to each other. An improperly done first meeting can sometimes lead to injury or emotional stress. Rats are individuals and each has its own way of dealing with newcomers. Some take to new rats with no problems whatsoever, some need a little time and assistance from you, and a few will not tolerate new rats at all.

Here we will discuss some basic introduction procedures followed by specific scenarios.

Basic Introduction Procedures


Before bringing a new rat home to your colony the first thing you must do is quarantine them to prevent the chance of illness to your resident rats. Quarantine is only effective when it is done at a separate location or at the same location if there is a separate air supply. Quarantine should last a minimum of 2-3 weeks. If the new rat shows any signs of illness take it to the vet. Quarantine will start again after the rat has no more symptoms of illness.
Never put a new rat in directly with your resident rats.

Alleviating scent

In most situations reducing or masking the rats natural scent will make the introduction easier. Some people use a dab of an aromatic substance, such as vanilla extract, on the rats to mask their scent to each other. For introducing rats that are more territorial or in a group you can bathe them first using baby shampoo or scented Suave shampoo such as peach or raspberry. When adding a rat to a group, bathe the new rat first. Add the resident rats one by one as you bathe and dry them making sure that you are close enough to supervise them. The kitchen counter is a good place for introductions when the bathing method is used.
If the rats become agitated and you are seeing too much sniffing then open up a can of tuna and give them a bowl of it. Not only will the tuna distract them it will also mask their natural scent more effectively. You can even rub a little of the juice on them to ensure that they all smell the same.

Neutral Ground

Place the rats on neutral ground where nobody will be put in a position to defend his or her territory. Do not choose an area where the resident rats play or free roam. Some good places for introductions are the bathtub, the kitchen table, the bed, or a counter top. If you are dealing with a baby or with a shy rat you may want to do the introductions on your lap. During the initial introduction you must supervise the rats. Your introduction phase may be many short ones or one long one. It depends on the age, sex, and personalities of the rats involved.
If an introduction is going well you can leave them together on the neutral territory for several hours to give them more time to adapt to each other.
During this initial phase provide them with food, water, and a towel to nap in.
The length of time for this step can range from anywhere from an hour, to an entire day, to every day for a week. If the initial meeting does not go well then you can separate them and try again later. Sometimes putting the rats in cages next to each other will help them get familiar without risking injury.

Returning to the Cage

When expanding your colony it is essential to provide them with a cage that is big enough to accommodate new arrivals. A cage that is too small will sometimes cause rats to behave aggressively either towards you or towards each other.
Before the rats are returned to their cage clean it well to remove any scents.
Use new bedding, new towels, new food, fresh water, and make sure all cage accessories are clean and scent free. Sometimes rearranging the accessories will help to keep the resident rat(s) from being territorial. Provide babies or smaller rats with a house with a small entrance that only they can fit through.
This will give them a safe spot to retreat to in the event they are being picked on. If they do not get along in the cage then backtrack to the neutral ground for awhile before trying it again.

Specific Scenarios


You can expect a certain amount of squabbling in the cage as the rats determine their pecking order especially from the alpha rat. In this instance it is not uncommon to hear occasional squeaking or see power grooming. As long as there is no actual signs of serious aggression, fighting, or injury this will usually resolve within a few days. You can use a spray bottle filled with water to break up any minor squabbles.

Sometimes it is the new rat that strikes out first.

Immediately remove any rat that is becoming aggressive. Wear thick gloves or have a towel to throw over the aggressor when removing him so that you will not be bitten. Signs that a rat is becoming aggressive include arching its back, puffing up, hissing, and pushing sideways against the other rat. Unfortunately, sometimes there are rats that are simply aggressive toward other rats. If the behavior is severe and the rat is a male you can try neutering him before reintroducing him to another rat. If neutering doesn’t help then he may just be one of those few rats that can not live with other rats.
If there is a resident rat that is fighting with a newcomer then remove the resident rat for a day. This will give the new rat a chance to make the cage his own and when the resident rat is reintroduced the tables will be turned making him the newcomer.


Occasionally you will encounter a rat that is terrified of other rats. The rat may cower in his house and only come out long enough to drink and grab up some food before darting back to safety. The rat may stand on his hind legs and squeal if any other rat comes near him. A scared rat may also be afraid of the other rats attacking him and attack them first. Rats who are obviously afraid have to be taken through the introduction process very slowly.

Introducing Adult Males

Putting new adult males together can be the most challenging of all the introduction scenarios. It is absolutely necessary to follow correct introduction procedures when doing this. Male rats tend to be more territorial when faced with another adult male than any other grouping. There are many adult males who live alone due to trauma from lack of proper introduction techniques.

Introducing Babies to Adults

Often adult rats make wonderful “uncles” and “aunts”. Even so, when placing babies with older rats you need to pay particular care to safety. There have been instances of babies being attacked and killed by adult rats. Be sure that the baby is at least 6 weeks old. If there is trouble with the introduction or if the rats are picking on the baby wait until the baby becomes a little older then try again.

During the neutral territory phase of the introduction it is wise to actually keep your hand on the adults back so that you may intervene quickly if there are problems.
If the adult male is sniffing at the baby excessively you can wipe some of the adults urine on the baby’s back, rear, and belly. For some reason a female rat will be the one to target the new baby by harassing it at every opportunity. This is traumatic to the baby and one or the other should be removed until the baby is older (8-10 weeks).
Occasionally you will find adult rats that do not tolerate youngsters well. If this is the case then it is safer to not place babies with them.

Introducing a Breeding Pair

When you put a breeding pair together you will not need to mask or alleviate scent. Put a box or house of some type into the cage that has an opening that the female can go through but that is too small for the male. This will give her a chance to get away from him if she needs to.
The best time for a breeding introduction is when the female rat is in heat. Signs that a female is in heat are an arching back with hind end raised, darting around in circles when her back is touched, and fluttering ears. A female that isn’t ready to breed will sometimes spurn the male’s advances. If he is too persistent one or both of the rats can be injured.
After the breeding you can put both rats back in their respective cages with little or no problems. If the other males show too much interest in the returning male then bath him to remove the scent of the female.
If you leave your breeding pair together during her pregnancy then you will need to bathe and reintroduce the male to his cage mates. Be sure to remove the male rat before the female gives birth so that she won’t become immediately pregnant again.

The Goal of Introductions

Remember, think safety when introducing. The ultimate goal is to provide companionship, not to create a stressful environment for your rats.


Introduction Cases and Photos

    Easy Introductions
    (These introductions were resolved quickly, without any injuries.)

    Figures pending

    Extended Introductions
    (These introductions took longer and were resolved without major injury.)

    Figures pending

    Problematic Introductions
    (During these introductions either an injury or death occurred. Not all were resolved.)

  • Fig. 1: Introduction involving territorial aggression with resultant leg bite wound. Successfully resolved. (Luna and Twix)
  • Fig. 2: Introduction involving territorial aggression with resultant neck bite wound. Successfully resolved. (Phi Adara)
  • Fig. 3: Introduction involving territorial aggression with resultant bite wound to ear. Successfully resolved. (Yasmine)


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