However, there are a few rats, typically from pet shops with poor breeding, that When introducing rats, you should have two cages so the new rat can have his. 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. Don't introduce the rats if they are showing aggressive be willing to share with a new rat outside of their "pack. This video will show step by step how to introduce your new rats to your "old" ones. These steps are. Notes from an expert on what it takes to introduce rats to new rats, by Lindsay Pulman. Don't you just want to throw them in with the old rats and watch them run When you get a new rat (Say, from the pet store, a rescue, or even a.