So you just picked up your new rats and want to introduce them to your existing rat(s). What's the best way to approach this? Here are a few helpful tips.
The very first step, without question, should be to quarantine your new rats. Even if you adopt your pets from the most reputable breeder, it is recommended that you quarantine all new animals for at least 3 weeks. You can see our quarantine procedure, and what problems to look for, here.
If they appear healthy at the end of the 3 weeks, they should be safe to introduce to your other pets.
We recommend moving the new rats' temporary cage in to the room you house your existing rats. Put their cages next to each other so they will be able to smell each other, but not reach out and touch. Do this for a day or two.
Next, switch their cages for a day or two - put the new rats in your existing rats' cage and vice versa. This way they are fully immersed in the other rats' scents.
It can be helpful to bathe all of your rats with baby shampoo prior to their introduction to reduce their smell. Introduce them to each other in a neutral environment and not an area your old rats normally roam or play in. An empty bath tub can be a great place.
Closely monitor their behavior during this time. Some squeaking or wrestling is normal, and the dominant rat will usually pin a new rat on its back to let them know who's the boss. As long as they are not actively trying to injure each other, let them work this out. If they are getting along you can leave them together for an extended period of time to better get to know each other, maybe even in the existing rats' play area (not a cage).
If they are not getting along, start them out with very short visits, offering treats to divert their attention. Some people have had success with dabbing a little vanilla extract on each rat after a bath so they all smell the same. With especially territorial or shy rats it may take several short introductions before you can safely house them together.
Rats are very social animals and, in general, they will all get along after a brief adjustment period and establishing where each rat's place is in the social hierarchy.
Once you feel confident that your rats are getting along, you can put them all in the same cage. Before you do this, however, make sure to thoroughly clean the cage to remove any scents. Replace bedding, clean all cage furniture, and wipe down the inside of the cage as you would for a deep clean.
Once this is done you can put all of the rats in the cage together. We would also suggest rearranging the cage, if possible. Make sure there are plenty of hiding places for them to retreat to if they are not getting along. If you are introducing younger rats it may be helpful to make sure they have an area they can retreat to that the larger rats cannot.