Safe Ways To Introduce Rats

What’s the best way to introduce new rats into an established pair?

Q: We have been housing two female rats from the same litter for the past two months. We’ve accepted them as family and they trust us as the same.
Last week, we met with someone who had four “accidental” litters and is still currently trying to find homes for the young rats and their parents. We took in two female babies (old enough to eat seed and drink from the water bottle) and a mother. On the advice of a veterinary technician, we tried introducing all rats immediately, and one baby was killed by an original. Said original acted aggressively toward the mother, who was accepting and did not instigate. We’ve since begun housing the two babies (we picked up another) and mother in a cage beside the two originals and switching the cage occupants frequently.
Over time, the second, and more timid, original rat has become aggressive toward the mother. The mother, who was very sweet and curious when we first met her, has become skittish to the point where it is difficult to handle her.
Tonight, four days after the new rats arrived, we tried to introduce the two original rats with the mother on neutral territory with a dish of tuna to inhibit their scents, but all three ignored each other. What can we do to integrate the mother calmly and the babies safely?
Both of the originals are hairless, the babies are fancy, and the mother is a patchwork who has a slim chance of being pregnant. The dominant will either charge her outright, without scratching, or wait until she’s sniffed the mother’s genitals, and then will bite and claw.
A: Right now you have far too much going on to try to introduce your five female rats. It’s always risky to try to introduce a mother with babies to other unfamiliar female rats; if there is any aggression expressed it will be the babies that will suffer. And since rats can be a little territorial about their homes, cage swapping usually creates agitation in rat relationships rather than familiarity. Unfortunately you must now deal with a very tense situation between your rat girls, and you need to let that settle down before you try introductions again.
Mom and her two babies need to be by themselves until the little ones are large enough to defend themselves against the bigger rat girls. If the cages are kept close (but not touching) it will allow a familiarity to grow between mom and your original girls, this will go a long way during the introduction process. It will also help repair the poor relationship that was created by the cage swapping.

After at least a month of the rats living like this, the little ones will be weaned completely it will be OK to allow all five rats to get to know each other on neutral territory. Once you’ve had at least a week of uneventful introductive playtime, you can allow them access to each other’s cages.

Take things slowly and don’t push the introductions. Watch the rats closely and their behavior will let you know when they’re OK to stay together permanently.

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Critters · Mice and Rats