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Pet Rats/What to look for in introductions



I’m in a newbie situation with my pet rats. My wife and I had two previous occasions where we’ve tried to introduce intact males. The first, when we really didn’t know what we were doing, was trying to introduce a six-month-old rescue rat to two resident one year olds. We followed all the steps online, but alas it was not meant to be. We found a new home for the rescue, and when one of the two resident cage-mates passed, and Artie, the remaining rat became depressed, we knew enough to try younger males. We got the babies from a breeder when they were six weeks old, and started the introduction process after a three-week quarantine. Three days later they were all peas in pod. To sum up: our two introductions to date were of one extreme or another.

Two years later and we found ourselves down to one rat once again. He seemed to be OK by himself but we know rats are social so off to the breeder we went. This time we came home with four brothers. They were eight weeks when we got them, and after a three-week quarantine we started the intro process. We had their separate cages close together for a couple of days and our resident elder, Jayne, did not seem phased at all. We then put them in a neutral environment, and things went well…some mutual sniffing and no dust-ups. We felt it was like Artie all over again and the whole gang would be moved into a single cage by the weekend. Since I’m writing this message that was not the case. We put them together on night two in an area the resident was used to playing and there was a little scuffle, no blood drawn, just a few squeaks and some boxing. We then went back to the plan laid out by multiple online sites: neutral territory for a little each day. There was one night incident free, and one night with a small scuffle. I wear thick gloves to keep the fisticuffs to a minimum.

Our problem is that we’ve only seen the two extremes, and my wife equates any fighting with “this will never work” as that was our experience. I know each case is unique, and this might be one where we end up with two colonies. My question is what to expect each day in neutral territory? What kind of fighting should I expect? How do I know what’s normal and what’s aggressive? So far I’ve noticed the resident is sometimes puffy, but will also calm down while the babies are still present. There has been no sidling or trailing and the skirmishes have been broken up quickly. Is there a way to tell what’s normal squabbling and what should be worrisome? What are the signs that I should proceed to the next step? What are the signs things will not work out? Should I let small altercations play out, even on neutral ground? My fear is that because I make a mistake, one of my boys will be injured. Are four youngsters too much stress for an older resident? The advice and articles online are all general…can you offer any advice specific to our case?

Thanks for your help!


ANSWER: Hi Ray, it sounds like you actually are going about things the right way, so you must have gotten some good advice from those websites.  

Introducing rats is always a bit scary because you just never know what to expect.  Sometimes a rat rejects all newcomers and has to live alone.  Sometimes, a rat will reject one rat but accept a different one.  Sometimes, what seems to be working well during introductions may turn nasty after 15 minutes.  So you always have to be on guard.  Gloves are a very good thing.  A spray bottle of water to keep handy is also a good way to break up a fight.

One extremely important thing for you to know is that you should never introduce babies younger than 12 weeks to an older rat because they are too small to be able to defend themselves if attacked.

I'm going to attach a link (below) to the very best website for introductions that I've ever come across.  Perhaps you haven't run across this one yet. It has tons of good information and videos and should be very helpful to you in recognizing everything from mild to extreme aggression.

For the most part, when you see poofiness and sidling, it is a sign that things might turn ugly soon, so it's a good idea to break it up at that point and calm the aggressor down before restarting.  It's also a good idea to have your wife there to help, each of you being responsible for one rat.  I've had introductions go well for a little while when suddenly the two rats in a split second become a rolling ball of squealing rats.  Should this happen, you must be ready to quickly break it up or someone might get hurt.

Have you tried putting a little vanilla on all the boys during intros so that they all smell the same?  Another idea is to do intros in a bathtub.  Fill it with a tiny bit of water, about 1/4 inch deep.  Place something in the middle of the tub that is above the water (an island of sorts).  Then place the rats in the water.  Likely they will be scared of being in water and all will seek out the island.  More likely than not, they won't fight on this island because they will all have the common goal of escaping the evil water in the safe haven.  This bathtub technique is one of the best I've run across.  If it works the first time, repeat it several more times the same way.  If all still goes well, the next time just place them in the tub with no water.  If they get along, you can try a different neutral area like a bed.  Going from this point to actually having them live together in one cage is sometimes a long process. If they do get along after these intros, you should consider getting a new and very large cage that none of them have lived in before, because rats are very territorial.  Also, the larger the cage and the more there is to do in the cage, the less likely there will be fighting.

If none of the above steps are successful after many tries, I would at that point assume that the aggressive rat will most likely need to live solo.  I  currently have a solo rat that would never accept another, and she is doing just fine.

Here is the link to that website:

I hope that I've addressed all of your concerns here, and what I might not have you will probably find the answer to on that website.

Please feel free to ask additional questions and do let me know how things go.  I hope it has a happy ending :)

---------- FOLLOW-UP ----------

QUESTION: Thanks so much Irene!

I have a few follow up questions if that's OK:

Regarding the bathtub island technique, should I still attempt it if it will probably stress out our resident male Jayne? He's two years old and a little squishy, but it's worth it if it'll help him get over his aggression.

Two, can you describe the process and indicators you used on your rat that won't accept new cage-mates? Specifically how that rat acted during the various stages of introduction, and what you looked for to decide that the intro wasn't going to work. Our resident Jayne is the only aggressor, and he doesn't seem to show any sign of relaxing during intros. He immediately puffs up, tries to sidle, and if I don't intervene there is always a rat-ball scuffle that I have to break up. I'd just like some pointers to look for to determine if Jayne is better solo.

My final question, we have our living room rat-proofed, and Jayne is used to coming out and playing on the floor. If we are unable to get him together with the babies, will it be OK to let the babies also play on the floor, separately from Jayne? I just don't want the fact that Jayne will smell them cause him too much stress. I think it should be OK since we do the cage-swap and he gets over their smell in that case in short order.

And I just thought of one really-final question: Is there any point to continue to do short intros even if we decide to keep them separate? Meaning there is no chance Jayne will mellow after six months or some random time frame?

Thanks again for all your help!

Hi Ray, from your original question, I didn't get the feeling that Jayne was that aggressive or stressed, but from your second question, I get a different impression.  You call him the "aggressor" and it sounds like he is ALWAYS aggressive and you say he doesn't show signs of relaxing.  

Well, because he is old, introducing so many (four) youngsters to him would likely be very stressful, as youngsters are quite hyper and he probably wouldn't be good with any of that.  The bathtub water would also likely cause him stress if he is not used to water.  You want to minimize stress on an older rat.  Stress can cause illness.  

The only thing that would probably make him calmer is a neuter, but do you really want to put him through a surgery at his age?  

I'm leaning towards having him live out his life solo and not to neuter, but the final decision is up to you.  I am only offering options and suggestions.  

When I brought home 2 young girls for my then 12 month old Lulu (the solo girl), introductions never went well and they were always in neutral territory.  They would start fine for the first few minutes but always turn violent, with Lulu poofing, sidling and then outright attacking the young one.  I gave up after several weeks of trying.

Since Jayne doesn't seem stressed if his cage is close to the babies' cage, if you choose to keep him solo, then having the cages close to each other would actually make him not a truly  solo rat.  Keep the cages close enough to each other so that they can all see, hear and smell each other, but far enough apart so that little paws and tails won't get bitten...perhaps 6 inches apart.  Rats communicate verbally at a level not heard by humans so they will actually be able to "talk" to each other and definitely smell and hear each other.  This is how I keep my Lulu and the other younger girls.

Because Jayne is alone, I suggest longer and more frequent out-of-cage times for him, and lots of time spent with you and your wife.  The youngsters need out-time too, but they have each other in the cage for companionship, so they could do well with an hour or two per day, as long as their cage is large enough and has lots of enriching items to keep them active and busy.  For 4 males I would recommend a Double Ferret Nation cage or something with similar levels and dimensions.  

Freeplay time on the same living floorspace is fine as long as the smell of the youngsters doesn't stress Jayne out.  If they are living in nearby cages, he is likely going to be used to their smells.  My Lulu and the young girls share the same play areas and they just sniff the floor a lot, especially in certain places, so I am quite sure they are smelling each other, but none of my girls are stressed by this.  In fact, I think this makes freeplay more "interesting" for them to explore the various sights and smells :)

I hope this addresses all of your concerns.  I don't mind lots of feel free if you need more help.

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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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