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Pet Rats/Introduction Stress



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!


Hi Ray,
When a rat has his fur puffed up there is the potential for aggression, so you don't want them to interact when one is like that, so when that happens, you either need to talk to Jayne and coax him to put his fur down, or separate them. You can say things like "Now, now, you need to be nice," "relax now," "calm down," "be gentle" which might be enough to get him to lower his fur. As long as his fur isn't puffed out, any fighting should be just scuffles for him to show the new boys he is boss. That is okay.

Typically what will happen is that during each session together there will be less and less scuffling. Sounds like you can probably go back to sessions in the play area, just being very vigilant to remove Jayne if he keeps his fur puffed up. When they can be in the play area together for an hour without any scuffling, they will be ready to go into the same cage. But,there may be some more scuffling there for a few days. As long as Jayne isn't puffing up, you can let it continue.

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Debbie Ducommun


I can answer any questions about pet rats, but you will probably be able find answers to simple questions more quickly on my website at If you have a life-threatening emergency you can try calling me at 530-899-0605. I am not usually on the computer on the weekend.


I have been "The Rat Lady" since 1985 and am recognized as one of the world's experts on pet rats. I have 3 published books and already answer lots of questions about rats daily.

President of Rat Assistance & Teaching Society

I am a monthly columnist for Pet Business magazine, and my writing has appeared in other magazines. I have 3 published books.

BA in Animal Behavior

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