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Pet Rats/Random rat fighting


Hi there! I have four adult female rats who have all gotten along and lived together for about 2 weeks now. I got them all a brand new café and put them in it all at the same time. Recently, we fell in love with a young dumbo rat who might be 7-8 weeks old. Only one of our rats, Uma, will go after her. However, it is only in their cage and when Ella, the baby, is trying to play with her. Do you think these two will ever get along, maybe once Ella is older? Also, since about two days ago, our Juliet has been going after one of our other rats Willa. Willa seems to be slightly older than Juliet, but we believe that Juliet is the dominant rat. We have identified their little scuffles as aggression because Juliet will puff her fur up and arch her back. Both will use their hind legs to push back their aggressor. Do you think the introduction of little Ella has caused this behavior in our older rats? Thank you for your help,

Yes!   Absolutely, the addition of Ella is the cause!   And please accept my apology for my delay in responding.

To understand the reason, you need to understand the way the dominance hierarchy works within a rat colony.  Basically, a colony is a group of rats that have already established their dominance hierarchy.  One rat has established herself as the alpha rat, or the boss, and all the other rats fall into place as beta rats, some being more subordinate than others, under the alpha rat.  This hierarchy allows them to live peacefully together, each knowing their "role".   When a newcomer is added to the colony, everyone's role gets thrown up in the air, and a brand new hierarchy must be formed.  A new alpha rat must be established.  This will usually be the same rat as before, but if the newcomer is very dominant, she may become the alpha, and fighting for subdominance will ensue amongst all the beta rats so until they all fall into place as far as their new roles.

Does this make sense?  This is a very interesting and complex topic in the rat world.  In case you are interested in understanding more about rat behavior in terms of hierarchies, I'm including this link to an excellent article on this topic.

Basically, you need to allow your rats to work out their new dominance hierarchy amongst themselves, barring extremely aggressive behavior where very violent aggression occurs or bloody injuries occur, at which point you need to immediately separate the fighting rats.   I recommend doing slow introductions in neutral areas with the group, repeating twice a day for 15 to 30 minute intro sessions.  This should go on until you see good behavior amongst the rats.  Only at that point should you move the new rat into the min cage.  Even if they get along in neutral areas, rats are very territorial and may strongly object to the new girl invading their cage.   That's why the main cage must be completely cleaned, all odors removed and everything rearranged before moving the new girl inside.  

I have to mention that in some cases, there will be two rats that will just never get along no matter what you try.  If neutral intros are unsuccessful after daily sessions for two weeks, chances are high that the ones that continue aggressive fighting just will never accept each othe.  At that point, I recommend another cage and moving 2 or 3 of the rats who DO get along into there while leaving the other group that also gets along in the original cage.  There really is no other solution if you wish to keep all of these rats.

There is lots of info on rat introductions on the Internet.  A good source is  I won't get into that topic to keep this reply brief and addressing your question and concerns.  

I hope this has been helpful to you.  Let me know if I can help you with anything else and good luck with Emma and your other rats getting along.

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Irene Murphy


I can answer a variety of questions regarding adoption and care of pet rats throughout their lifetimes, including questions about their health and well being, temperment, diet, bedding, cages, toys, etc. I will try to answer your questions to the best of my ability in a timely manner and I have an abundant amount of resources to help me to help you with your pet rats. I love rattie pictures, so include pics with your question if you can. You may ask me medical questions, but please be advised that I am not a vet. I may use my resources to answer some medical questions, however, I will need to refer you to your local vet with medical questions that I feel I am not qualified to address.


I have been a huge rat enthusiast for many years. Since becoming a rat owner, I have educated myself in all areas of pet rats from every resource I could find including the internet, books, conversations with local exotic vets, as well as several local rat breeders.

I have a college degree but not in the area of animals. I have obtained my extensive experience and knowlege of pet rats all on my own because in my eyes, pet rats are the most interesting and fascinating creatures you can ever imagine to have as pets. I also am saddened by how mislabeled and misunderstood these amazing and extremely smart animals are by the majority, and my mission in life has become to educate and change as many people's perceptions of rats as I possibly can.

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