Understanding Rat Behavior: Are My Rats Playing or Fighting?

by Alison Blyth
Understanding rat behavior: Are pet rats fighting or playing?

For the last few weeks, my life has been one long session of rat introductions. 2018 brought five new rescues into my home, all lone rats who need to make friends with the Horde. Understanding rat behavior can be a bit tricky. Let’s look at some of the behaviors that rats show when they meet, and how you can work out if they are fighting and being aggressive.

Why has my rat fluffed up their fur?

If a rat is angry or is feeling defensive of its territory (a cage or play space), then they will often fluff up, with the guard hairs on their coat standing on end (the scientific word is piloerect, but I prefer floofed). This makes them look bigger to the other rat and is a sure sign that a rat is feeling aggressive. It’s easy to spot as the rat literally looks like a toilet brush (the behavior is known as “bog-brushing” in the UK rat fancy) or a powder-puff.

Whether or not I intervene when a rat fluffs up depends on the other behaviors they are showing. I had one boy (Moose, or as he was known for several months, the floof-moose) who would bog-brush at the slightest thing, but not go anywhere with it. However, if a fluffed-up rat is actively facing down another, then I look at what else they are doing.

Pushing, sidling, and bum-barging

Rats don’t want to fight and risk injury unless they have to, so they try to win arguments with dominance behaviors. One is to walk sideways into the other rat, bottom first. This is known as sidling or bum-barging. Often the aggressive rat will crowd the other into a corner, or even try to push them off a shelf. The threatened rat may run away, freeze, or push back. I watch these behaviors very carefully and break them up if the rats are becoming stressed, or a fight starts.

My rats are boxing

Boxing is where two rats face-off by standing on their hind-legs, pushing at each other. It means that both rats are cross, and neither is willing to submit right now.

If this happens in a happy, established group, I don’t worry – it’s usually a brief argument about who is boss. On the other hand, if one rat is quite new to the group, or if one or both of the rats has fluffed up, it can be a sign that a fight is about to start, so I watch carefully, ready to intervene if needed.

And now they are kick-boxing

Kick-boxing, where one rat hits the other with their back legs, is a way of exerting dominance. It usually comes after sidling or bum-barging. Again, in a new rat situation, it can be the first sign of a fight.

It can also be used as a way for a dominant rat to exert authority over her group. I had one tiny girl called Feegle, who was the boss of a group of neutered boys – even though she barely weighed 200 g, and they were all half kilogram lumps. At regular intervals, she would go round the group, giving each boy a firm kick in the head. They immediately submitted as they had learned the hard way that the alternative was being beaten up by a tiny martial arts expert until they gave in.

My rats are mounting each other! And they are both boys!

Rat behavior - is it aggression or play

In rats, as in many animals, dry mounting or humping has nothing to do with sex, and everything to do with dominance. Girls will do it to girls, boys will do it to boys. It means “I’m in charge”, not “let’s make babies” (unless you have unneutered boys and girls together, which is not a good idea). Mounting is very common in play, especially in younger rats. It isn’t something I worry about unless other signs of aggression are present.

Flipping, pinning, and grooming

This is a way to exert dominance, either over a new rat, or in an established group to remind everyone who is in charge. The dominant rat (or the rat who wants to be dominant), approaches the other and pushes them over, then pins them down and grooms either their neck or belly. The submissive rat will lie down and freeze until it is over.

Most of the time, especially in established groups, this causes no problems at all – it is just a natural way for rats to show who is boss. However, if the two aren’t agreed on who is dominant, it can turn into a fight.

My rats are chasing each other

Chasing is completely normal rat behavior, and often just a sign of play. My rats often chase each other around their free-range area for fun. I only worry about it if the rat being chased is becoming very tense and stressed, or if the rat doing the chasing is showing other signs of aggression like fluffing up, trying to bum-barge etc.

Should I split up a rat fight?

This is difficult to answer, as it depends entirely on context. On the one hand, no one wants their rats to get injured. On the other, rats live in groups with a hierarchy, and sometimes that hierarchy needs to be sorted out. A lot of people use the “no blood, no foul” rule, which means they don’t intervene unless one rat gets hurt. However, the problem is rat fights are big spinning balls of flying fur, and you really can’t tell if someone has been hurt until afterwards.

I only ever get fights during introductions with new rats, and I do break them up. I watch for any of the aggressive behaviors discussed above and split the rats up if it turns into a fight, or if one rat is looking very stressed.

Never, ever, stick your bare hand in the middle of a rat fight! It can be tempting as you don’t want your babies to be hurt, but if you just plunge your hand in the middle, the one getting hurt will be you. If I am introducing new rats, or if two rats are showing behaviors that might lead to a fight, I get a piece of cardboard, a newspaper, or a thin book and have it ready. If a fight starts, I put the barrier into the middle, and gently push the two rats apart. Generally, once they can’t see or interact with each other, they will calm down.

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Jennifer Rydell June 1, 2019 - 6:06 pm

I am learning a lot about their hireachy by reading what you and others placed online.it is very helpful thank you.

Monika June 2, 2019 - 10:28 am

I’m glad you find it useful 🙂 Thank you for visiting!

Megan August 11, 2021 - 11:46 pm

The white rat keeps getting all puffy and then starts to fight with the new baby one,
She also gets the black one riled up and then the black one bites the baby one and they recently bit a big hole in her neck and right arm, I then separated them and fixed the baby one up, the black rat is fine with the little one on her own but when the white one is with them it gets ugly after a while,
So I have a small cage that the little girl is sleeping in and her smell is all over the cage so when I put the little baby in with the black one I put the white one in the small cage so she can get used to the smell of the baby one.
I just hope they stop biting her there was a lot of blood last time

Alison August 12, 2021 - 3:03 am

Hi Megan,
I use a hormonal implant called superlorin for rat-aggressive girls. It can help quite a lot. Spaying is also a more permanent option, but a full surgery.
It’s also worth looking at how you are doing the intros – they need to be on completely neutral territory and not in a cage, and not have any areas (like houses or tunnels) that are defensible. I use the carrier method – http://www.isamurats.co.uk/the-carrier-method.html
Hope that helps

Ben July 15, 2019 - 3:01 pm

Very cool, exactly what I was looking for as I’m currently introducing some new younger rats to my older rat that lost his brother.

Just wondering, during some of the pinning down there is some skin pulling / holding with their mouth. I stop them at this point because I don’t want anyone injured. Is this just dominance or is this one trying to injure the other?

Alison Blyth July 27, 2019 - 12:36 pm

It’s hard to say without witnessing it. I do sometimes see skin pulling in playfights (I have one girl who is a terror for it – always on the neutered boys). But equally it can be a precursor to biting. That isn’t a very helpful answer I know! But ultimately, I’d go with your gut. There is no harm in taking intros slowly if you feel one rat is being picked on or very stressed by them.
One thing I have found useful is to introduce them in a carrier, and pick it up and walk around if they get too argumentative. They tend to stop arguing to figure out what is going on. I’ve even taken them for a drive in the carrier, as I’ve found the mild stress has a bonding effect.
Good luck!

Kenzie LK Stoner October 22, 2019 - 2:30 am

My rats (Moose and Chewy) keep fighting or something. Moose (the biggest rat) keeps crowding Chewy in a corner and biting him or something he us even trying to push him off a ledge. But Chewy keeps squeaking and trying to run away but Moose just keeps trapping him and doing it again. Is the squeaking coming from Chewy pain or him trying to say to get the hell off of him.

Alison Blyth October 23, 2019 - 2:25 am

Hi, it’s not possible to say if the squeaking is pain or just objection to the treatment without knowing the rats. It could be either or both, especially if there is biting. However, what you are describing is heirarchical fighting / dominance bullying. A small amount of it that settles down is perfectly normal in rats sorting out their heirarchy, but if it is persistent, or if Chewy is being injured or stressed, then action needs to be taken. My choice in these situations is to neuter the bully or both (I tend to neuter all boys unless there is a medical reason not to) – however, that is a personal decision for the owner as not everyone is comfortable with the (small but real) risk or has an appropriate vet. Another option is to go back to square one and try reintroducing them using the carrier method http://www.isamurats.co.uk/the-carrier-method.html which can help if the fights are due to territorial issues in the cage.

Desiree December 19, 2019 - 5:57 pm

I’m trying to breed my albino rats. 2 females 1 male. The males to me seems to aggressive towards them. The one female had hair loss on both side of her side. He sniffs there area then gets to chasing them but the females squeak and seems like it to rough. Any advice don’t know there age I got the the first week of November of this year and there in same cage always. Thanks

Alison Blyth December 20, 2019 - 3:37 am

Hi Desiree

It’s good you’ve spotted this. Hair loss isn’t a normal part of dominance, or mating, so there is something wrong here for your girl. The most likely cause is barbering. This is where either the rat pulls / chews their own fur off, or another rat is pulling their fur out as a bullying thing. Barbering is an unhealthy behaviour that indicates the rats are feeling stressed. The other possible cause is mites – that’s more likely if she is scratching an abnormal amount – however again this is a sign of stress, as all rats carry mites (as do all mammals, including humans), but they flare-up symptomatically if the rat is under the weather.

The first thing I’d do is look to fix this problem, rather than worry about getting a litter right now. A stressed female rat is less likely to become pregnant and more likely to reabsorb (miscarry) or reject her babies, or become hostile to her cage mates, so everything benefits from getting her healthy and happy first.

In this situation, I would split them into single sex groups, make sure everything is right in their diet / environment (cage size, enough engagement etc), mite treat them, and see if her fur starts to regrow and they all settle down. That will also give you time to see if either girl is pregnant already.

In terms of breeding, although the old advice is to keep two girls with one boy, we now know this isn’t the best way to do it (it’s how rodent farms do it because it maximises “product”, but welfare is often not a priority in those conditions). The problem is that if the male always lives with the females, the girls will have repeated pregnancies back to back, which is very exhausting to their bodies and massively raises the risk of health problems. There is also the risk of the male being hostile to or even killing the babies, and of the females becoming very hostile to the male.

So, it is much healthier and happier for parents and babies if the adults live in single sex groups, and a male has the occasional sexy weekend in a breeding cage with a female when she is in heat, and healthy to breed.

I personally don’t recommend breeding from rats of unknown age / background, as there is no way of knowing about their health, and the chances of litters with serious health problems are increased. As an example, I took in a pregnant girl in 2018 who had been mated to her brother by the previous owner – no other info known about them. We’ve now lost 5 of the babies during youth or middle age to either very nasty cancers or heart failure. Breeding females of unknown age can also be a risk as if they have their first litter too young or too old it can cause them serious health problems and increase the risks during birth. So, my advice to people looking to breed is always to join local clubs, and source rats from lines where the existing breeders know about their genetics. Joining the National Fancy Rat Society (https://www.nfrs.org/) is a great resource for people wanting to breed, as their members only breeder’s forum has a huge amount of information, as well as support from very experienced people. It’s a uk organisation, but has international members.

There is also some useful information on breeding here: http://www.fancyratsforum.co.uk/viewforum.php?f=15

All the best!

Natalie January 10, 2020 - 7:29 am

Hello I have recently introduced 2 new rats to my boys and I can’t tell if it’s going well it’s only been 2 days but my eldest boy is doing a lot of chatting and bum bardging, I think he might be petrifying my newest one, before the two newbies he was fine he still lives with his friend and they get along fine, one of my new rats tails started to bleed and I’m so unsure and am scared something worse might happen, I need some advice.

Alison January 11, 2020 - 7:52 pm

Hi Natalie,
It sounds like your eldest boy is feeling territorial, and there are fights resulting in the newbie’s tail being bitten. If the new rats is getting injured or stressed, it might be necessary to go back and start again from scratch. Intros can take a while and sometimes it is necessary to go very slowly.
It’s very important to do intros on neutral ground, not in the existing rats’ cage, and to keep furniture that they can defend (tunnels, boxes etc) to a minimum to start with. I use the carrier method, which is explained here http://www.isamurats.co.uk/the-carrier-method.html
Good luck!

Christine January 16, 2020 - 1:28 am

Hello, I originally got 2 males then a couple of months later I decided I wanted more so went to the same breeder and ended up getting the last 4 brothers out of their litter. At first intros went well as long as they were in neutral territory, but then the more they were around eachother, the original 2 started to show all of the signs listed above (the one more than the other though). He will be a constant fluff ball the whole time they are together plus he would grind his teeth, box, push and sideling, as well as stalk the new guys so they couldn’t move without him attacking or mounting. They couldn’t even take a drink of water! I finally gave up on intros and have them in separate cages, but I wish there was a way to put them all together since I have a double critter nation with lots of room for them all.

Alison January 16, 2020 - 10:49 am

Hi Christine,
You’ve got two main options for getting them together – the first is to start intros from scratch all over again and go very slowly through the stages (I use the carrier method which is linked in the reply to the comment above yours). Sometimes an intro that doesn’t work out the first time can go better later. For one boy here, it has taken till the third round of intros to get him settled in a group (and he’s neutered! But also a blue floofy menace with no common sense).
The other option is to neuter the bully. That’s always a personal decision for each owner, as all surgery carries a risk and it depends on what you are comfortable with and how experienced with rats your vet is. However, it is very effective in resolving bullying behaviour. I leave the neutered boy in his existing cage for a few weeks until his hormones subside, and then intros are done again from the start.
Good luck!

Hayley January 16, 2020 - 3:53 pm

Thank you for your informative post!
I have three boys at 7 months old, have always been together and have a lovely bond with a fully established hierarchy. They all sleep together and play fight sometimes but it’s always been obviously non violent. In the last week one of them has had a complete change in behaviour, he is very aggressive to both of the others, he is normally very shy and cuddly but is now acting very erratic and is attacking the others in what seems to be a very violent way at any opportunity, to the point that the other two are actively avoiding him and they no longer all sleep together. I have been advised that as they have now entered their ‘teenage’ age range this is likely down to hormonal aggression and it would be an idea to neuter him. I understand you can’t see the behaviour but would you say this sounds accurate and that neutering would be a good idea?
None of them are neutered and I hadn’t even thought about doing it until now, and it would only be this boy I would be neutering. I just want to avoid any serious injuries and get on top of it as soon as possible to avoid it possibly having a negative affect on their group dynamic and the bond they have.
Any advice would be greatly appreciated!

Alison January 17, 2020 - 1:02 am

Hi Hayley,
Yes, unfortunately it sounds like you have a teenage boy acting out, sulking and slamming his bedroom door. It would be a classic case for neutering which is very effective in resolving this sort of behaviour (it usually takes about 3 weeks afterwards for the hormones to drop properly).
It has to be your decision, as all surgeries and anaesthetics carry a risk – but it’s much smaller in the hands of a good vet, so it is worth finding a vet who is experienced in the procedure. I neuter routinely so to give some idea, I’ve neutered almost all my boys (except where medically contra-indicated), and lost only one to it in 20 years (he came through the surgery, but had a heart attack while in recovery). I would personally do it in this scenario.
Good luck!

Danielle January 21, 2020 - 9:34 pm

This is helpful thank you! I am doing intros with 4 babies and my one 2 year old. Everything in the carrier was good, moved them to a small cage next for 4 days and they were all good there too. Have moved them to a bigger cage (slightly bigger than previously) and they just keep fighting! I don’t know why because they were fine in the others. It’s hard to know whether to stay strong and let them fight it out or to separate.

Alison January 22, 2020 - 2:24 pm

Hi Danielle,
I’m having exactly this problem with my boy Rincewind (aka the blue floofmenace) – I can do intros in a carrier and small cage and then it all falls apart as soon as it gets to the bigger cage. The only solution I’ve found (although it is a work in progress with the floofmenace) is to take the process more slowly, and stick with the smaller cage for longer. so they get really bonded before they have more space to dispute.
Good luck!

Apryl April 4, 2020 - 4:56 am

Hi I have a dumbo rat and recently bought a smaller hairless/patchwork rat that is basically defenseless the bigger one (Arthur) pushes him holds him down and at first was only grooming him but now he won’t leave him alone Arthur has been a only rat ever sense we got him but he was raised with other rats I didn’t know if it was because he was hairless or what . Are they playing or fighting and will it end soon or no? Side question I don’t know if you’d know this but my bigger rat has red crust-ish stuff around his one eye but not the other and it’s never the other eye only the one do u know if this is serious or no, but either way thanks sm

Alison April 5, 2020 - 2:52 am

Hi Apryl,
With the behaviour, how did you do the introductions? I favour the carrier method (http://www.isamurats.co.uk/the-carrier-method.html) for bonding unrelated males as the small space takes territory out of the equation. It sounds like it started out as a dominance thing, but may now have progressed to bullying. The normal options are to redo the intros more slowly, or, if that doesn’t work, consider neutering the aggressor (there’s info on the pros and risks of that in a comment reply above – it’s an individual choice). It won’t be because the little guy is hairless, but just because they are unrelated and not yet bonded.
For the side question, the red stuff is porphyrin, which comes from a gland near the eye when the rats are stressed, unwell, or the eye is irritated. One-sided porph in my experience has either been a sign of underlying resp issues, or an irritation (like an ingrown eyelash etc) to that eye.

Samantha D May 22, 2020 - 3:31 pm

lol if i hear one mlre squeal im going to go insane all they seem to do is have a good old fight

Maz August 6, 2020 - 11:09 pm

This is really helpful, as a new rat owner I was worried about my boys as they were pinning and grooming and couldn’t find any useful info of whether this was bad or not. Thank you

Maz August 6, 2020 - 11:11 pm

I’ve had them for about two weeks and the less dominant one will has the occasional porphyrin from his nose and sneezing, do you think this is normal at this stage or should it have gone by now. He generally seems very happy and relaxed

Alison August 8, 2020 - 2:59 am

Hi Maz, After 2 weeks, I’d probably get a porphy nose and sneezing vet-checked just to be on the safe side – especially if he doesn’t seem stressed.

Carrie August 19, 2020 - 7:52 am

I need help. I have two boys we got as babies and have had for 6-7 months now. They have always played pinning and grooming but it has always been just play. However recently I noticed scabs in the cage and squeeking louder when the grooming is happening. I have them both a date in a few weeks to get neutered but tonight was the biggest squeak yet and the smaller of the two has blood on his side. So my question is should I separate them in the meantime? I have a double critter nation for just the two of them so they have plenty of room.
Another separate issue- They are fine with playing with me and my teenage kids, but sometimes they just bite and draw blood. One was just snuggling with me and playing with my hair and then suddenly just took a chunk out of my ear. He wasn’t grooming but yet he wasn’t being aggressive either. They have both done this type of biting since they were babies. There seems to be no rhyme or reason for it. We have tried squeaking loud to show them it hurts and it just doesn’t seem to help. They do it the most with my daughter, but they have done it with all of us. We take them out at least once a day and some times two times and they seem to enjoy it and us. I just don’t get it and it has come to the point my kids don’t want to do anything with them because you never know when they are going to bite. I made a giant playpen out of cardboard and I sit with them and give them a pea fishing bowl or some corn on the cob and they run around and play and they crawl on me. The other ways we get them out to play is we put boxes and play stuff on the table while my daughter is doing homework and I draw or something and they run around or I take then one at a time and sit in my recliner with then and they explore and snuggle a little bit. Sometimes we put the cardboard surround around their cage and let them get out and run around and go back in whenever they want and they seem to like that too. I just don’t understand the biting, everything I have read everyone says rats don’t bite unless they are aggressive, but there is no lunging or attacking. They are calm and hanging out, then bite, then just look at you like nothing happened. They don’t bite and run, they act just like nothing happened, so weird. I should also note that they do like to groom us, they lick and nibble ours nails but always gently and the bites are never at these times.

Alison August 26, 2020 - 6:02 am

Hi Carrie,
I’m sorry to hear you are having problems, but it sounds like you are doing all the right things. The good news is that the kind of random biting you describe is often a sign of hormonal idiocy in rats, and every case of it I’ve encountered has been cured by neutering. So hopefully it will settle down when the testicles go. You can think of it as the same kind of boundary-testing that teenage kids can get up to, but rats use their teeth.
If you are worried one boy is going to get injured, then I’d personally separate until they’ve been neutered. After neutering, I wait a couple of weeks for hormones to drop, then reintroduce them. If they are very hormonal, it can take a bit longer, so don’t panic if there is still some tetchiness at the 2 week mark.

Olivia March 28, 2021 - 7:19 am

I bought 3 babies from a breeder yesterday and we decided to get 2 girls and 1 boy since they’ve always been in the same cage we decided to keep them in a cage together, but I’ve noticed the male will bite at the littlest females ear and pull her, and drag her to another part of the cage. They did show sign of not wanting to submit but he continues to do it, but he won’t do it to our other female.

Alison March 29, 2021 - 5:58 am

Hi Olivia,
Firstly, I would split the boy from the girls – they can get pregnant at that age, and even if you are planning to breed, they need to be housed separately as otherwise the girls would be permanently pregnant or nursing, which is very bad for their health. They are also too young for pregnancy to be good for them (I don’t breed girls until they are 6 months old, and they only have one or two litters in their lives). And of course, if you aren’t planning to breed then you don’t want them to get pregnant at all! The little boy will need a separate cage and a same age companion – it would be worth talking to the breeder about what you want to do. Hopefully they aren’t pregnant yet, but keep an eye out for weight gain in the girls beyond what you’d expect for a growing rat (ie. if they get bigger and fatter faster than the boy) as that is a sign that they are. Rats are usually pregnant for 23 days.
The behaviour maybe because he wants to mate and she doesn’t.

Ellen April 28, 2021 - 3:09 am

I have 3 male rats and they’ve been together since they were about a month old, they’re now about 9 months, one of my rats, ironically the smallest one is always pinning down my other rats and i hear constant squeaks although they’re not usually super loud. He’s never been aggressive toward me and he loves to cuddle but as soon as i put him with the others he’ll chase them, mount them, and pin them down. I feel like by now they would’ve already settled the dominance thing and i don’t think i should be too worried because i’ve never seen any blood drawn, only a couple tufts of fur. Do you have any thoughts on if i’m overthinking or are they still just trying to establish the hierarchy? ps. none of them are neutered

Alison May 3, 2021 - 7:04 pm

It sounds like he’s not the dominant rat, but he wants to be! The main thing to look at is whether his behaviour is causing the others stress, or whether they just shrug it off. Neutering is an option, and reduces that sort of behaviour in most, but not all, cases (glares as Gaspode the wonder rat, who has been neutered for over a year and still pulls this rubbish on his girlfriends, although they mostly just kick him in the head in return).

May July 24, 2021 - 6:48 am

I have two 2 month old boys that have always been together. The more dominant one is very affectionate with my other rat, but always stands on and bugs him when he sleeps. Is this weird or am I being paranoid?

Alison Blyth July 24, 2021 - 7:35 pm

Hi May,
At 2 months old that just sounds like he wants to play and is being an annoying small child about it. Rats standing on / trampling other rats while they sleep is pretty normal. I wouldn’t worry about it as long as no one is getting hurt or stressed.

tourell September 2, 2021 - 9:05 pm

I have almost a year old Rat baby named Finn, he lost his older brother earlier this year and after a week or 2 I decided to look around for some rat buddies to give him company. I got 2, one dominant and one beta. At first the beta got along Finn and they were able to sleep next to each other and even eat food next to each other. The dominant one would always cause fights and even lash out and bite humans but is also very relaxed when lying on my chest. I tried reintroducing them to Finn but the beta one started bullying him and he made noises I never heard before, I seperated them and tried to give Finn some food or snacks to calm him down; he was frozen for about 10minutes and when I took the other rats out of the room he finally came down to eat and drink.

My question is, since his older brother the dominant one passed on first and he never really seemed comfortable on his own is it a bad idea to introduce him to new rats? He’s very loving and comfortable with me he just doesn’t like interacting with other rats.

Alison September 3, 2021 - 2:03 am

My approach in this situation is to confiscate the bullies’ testicles. This is classic hormonal rat aggression, and neutering usually fixes it and allows them to have company (although it is best to leave 3 weeks post-neutering before attempting intros). Obviously whether to neuter is a personal decision that only you can make – there is a small risk with any op or anaesthetic, and it needs a vet with experience of rat surgery.
The other thing to look at is how you are doing the intros – environment can enhance bullying due to rats defending territory – I use the carrier method here http://www.isamurats.co.uk/the-carrier-method.html, although it isn’t always suitable if the rats are getting violent with each other.
Hope that helps,

Samantha O’Loughlin September 4, 2021 - 12:50 pm

Very helpful article thank you so much!! Also everyone who put in their own questions. Learning a lot for my own ratikens


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