Introducing pet rats to each other

From time to time you may need to introduce a new rat to an existing group, perhaps to replace one who died, or because you have decided to increase the group size. Rats can usually be persuaded to adopt newcomers into the group, but it is important to get the process right to avoid injury and stress. Never put a new rat in directly with your resident rats.

Quarantine your new rat

When you first get a new rat, it should spend 2-3 weeks in quarentine to ensure it won't infect your existing rats with something. Ideally this should be done at a separate location. However if this is not feasible try to ensure that the quarantined rat is kept far enough away that it is not breathing the same air. If the new rat shows any signs of illness take it to the vet.

First introductions between rats

When you introduce rats, do it on neutral ground. Existing rats will vigorously defend their territory if you put a new rat straight into their cage or find it where they are used to playing. A bathtub might be a good place. Reducing or masking scent will help make things easier. Put a small drop of a smelly (but harmless) substance such as vanilla essence on each rat. Actually bathing the rats can be a good way to reduce scent and an opportunity for the new rat to be introduced as you bath all the rats one by one, unless your rats hate having a bath.

During the initial introduction you should physically supervise the rats. If things go well you can leave them together on the neutral territory for up to a few hours (providing food, water and somewhere comfortable to sleep. You may need to repeat this step a few times, or keep the sessions shorter if introductions are more fraught. Once you are confident that the rats will accept each other on neutral ground it is time to get them together in their permanent home. Prepare the cage by thoroughly washing it and all the accessories etc to remove the scent of the existing rats. Make sure you put in new bedding, food and water. Changing the contents round can also help. The idea is to reduce the cues that trigger the existing rats to defend their territory. If the rats do not get on in the cage then go back to the neutral ground stage and repeat as necessary. Sadly a few rats will not accept newcomers, so in a small number of cases no amount of work will produce an integrated colony. In these cases you will either have to have two colonies or see if the new rat can be rehoused.

Things to watch out for

  • You can expect some squabbling as the rats sort out their new pecking order. A certain amount of squeaking and forced grooming is fine.
  • If you need to break up a more serious fight, have a water spray handy.
  • Remove an aggressive rat from the cage, but use gloves or a thick towel if you don't want your fingers bitten
  • If one of the existing rats is aggressive, try putting him/her somewhere separate for a day, so that he feels less territorial about the cage.
  • A few rats are terrified of other rats and will not let them anywhere near. These rats have to be taken through the introductions very slowly.
  • Introducing adult males to each other is the hardest scenario. Be very careful to introduce them properly and make absolutely sure they accept each other before leaving them together in a cage. This is the scenario with the highest chance of failure.
  • Adult rats will usually accept babies over 6 weeks. However adults will sometimes attack babies. If they do, remove the baby for its safety and wait until it is a little older before trying again.