5 Surprising Reasons Why Your Guinea Pigs Are Suddenly Fighting

So, there’s trouble between your guinea pigs that came out of nowhere. And now you’re wondering why your guinea pigs are suddenly fighting.

With many potential causes for this behavior, it is important to know how to stop them from fighting so you can keep the peace in your home and give them a happy life. I did some research and some causes of sudden (or unexpected) fighting are:

  • Separation
  • Sudden Illness
  • Teenage Troubles
  • In Heat
  • Old Age
why are my guinea pigs suddenly fighting

Now, these aren’t the only reasons why some guinea pigs fight. But, these are the main reasons why some guinea pigs seem to just fight and you have no idea where the aggression came from.

Let’s look at these 5 reasons why your guinea pigs may be fighting suddenly in more detail and talk about what you can do about it.

1. Separation

So, you had a lovely matched pair of piggies and for some reason, they had to be separated.

Then you tried to reintroduce them (ya know, because they had a great thing going) and to your disappointment, they’re rumble strutting and nipping at each other.

You think: “What gives? It’s like they don’t even recognize each other!”

Yeah, well. In a way, they don’t.

As herd animals, guinea pigs have a social structure based on a hierarchy. Someone (usually the most dominant cavy) is the one in charge. Then everyone else falls into place – or fights break out an your piggies have to be separated.

If you suddenly bring in a new face, (or even a previously familiar one) the pecking order is thrown off and everyone scurries about to figure out who’s on top of the social heap.

So, each time cavies are separated their hierarchy is destabilized. That means the entire “who’s in charge” process has to be re-established. And a power struggle for status needs to take place.

What To Do:

This is a little tricky. There’s really only two things you can do to prevent fighting in this situation.

  • Avoid separating your little friends as much as possible. For serious medical conditions (like recovery from surgery, etc) you might have to separate them. But if you can, avoid separating your cavies for any other reason. This is especially true when the piggies are just getting to know each other, but even if they’ve lived together for years – keep them together, so you can preserve their relationship
  • Treat the pair as a newly introduced set. Do it gradually and in a neutral environment. Clean out the cage with a water and vinegar mixture and rearrange it. Make sure you have two (or three) of every hut and food bowl. Only use huts with two exits. That way the submissive cavy can get away from the dominant one without having to fight.

2. Sudden Illness

Sudden, unexpected illnesses have caused fall-outs between piggies to their pet parents’ dismay. Let’s look at these scenarios one at a time, and how to resolve them.

Bullied Sick Guinea Pig

Cavies are excellent at hiding illnesses from us. It’s another way they keep themselves alive in the wild.

Predators will try to catch a sick or weak critter. So, your piggie may look healthy and strong, but they could be hiding an illness that will only get worse.

Guinea pigs aren’t as good at hiding illnesses from each other. What sometimes happens in this case is that your guinea pig will suddenly become sick (not good).

The other cavies will quickly realize how vulnerable your piggie is (and try to sort of shove the sick guinea pig out of the group).

Then, a bully may decide to harass or bully that sick piggie until it finally retaliates!

It’s not the illness itself that caused the fall-out between them; it was the bullying that caused retaliation.

A Cranky, Sick Guinea Pig Is Mean To The Other Ones

In this case, the reverse happens.

The pain and discomfort of being unwell or in pain can cause a cavy to be very grumpy.

And, a grumpy guinea pig will obviously take out their anger on the other piggies – especially if the sick pig is the dominant one of the group. But the illness is what actually caused the fall-out in this case.

A few common illnesses that might make your guinea pig grumpy:

  • Ear Infection: Ear infections can be very painful, and it’s not hard to see why that might make a cavy cranky. When an ear infection is bad enough to cause pain, it can require antibiotics. The vet will prescribe anti-biotics that need to be given orally.
  • Ovarian cysts: Guinea pigs that have ovarian cysts (growths on their ovaries) often have issues with infertility. This is very painful. Over time, this can cause your guinea pig’s hormones to become imbalanced and lead to mood swings (and yes, might cause fights to suddenly break out).
  • Mites: Mites are highly contagious parasites that affect the skin. It can make your guinea pig itch beyond what you can imagine, and they’ll be very irritable.

What To Do:

Give your guinea pigs weekly health checks. It’ll be a lot more difficult for them to hide an illness from you if you’re already looking for it.

Weigh your furry friend every week and keep track of any sudden weight loss.

Get to know your guinea pig’s normal behaviors and habits, so you’ll notice any behavioral changes.

If you see that something looks off, ask your vet to take a look (particularly if the symptoms don’t seem normal for your guinea pig).

why are my guinea pigs suddenly fighting

3. Teenage Troubles

Just like human beings, all guinea pigs go through puberty. It starts when they’re about 8 – 10 months old.

And, oh man this is a tricky time for piggies because it’s the stage when they’re more likely to start fighting with each other.

In fact (and this may come as shock to you…or maybe not if you have teenagers yourself!), once your piggies hit puberty, chances are high that there will be more squabbles between their cage mates.

Why? Well, here’s what actually happens:

At this point, the teenage piggies’ body is full of testosterone – which makes them super aggressive.

And because they have raging hormones in their system, the teenage piggies are usually going to challenge the dominant piggie. It doesn’t matter if they’ve been getting along ever since the teen pig was a baby pig.

The teenager piggie is going to push boundaries, test the waters, and assert their authority (or at least what they think is their authority) over the other guinea pig.

It’s all perfectly natural.

And it will calm down once their testosterone settles around 15 months old or so.

Good news: Extreme fall outs and fights are rare.

Bad news: It’s a nail-biter of a time period.

What To Do:

To try to keep the peace during this volatile time period and to avoid sudden fights, try doing the following:

  • Get a bigger cage. The more space, the better. That way everyone can keep out everyone else’s way. And tempers can cool off.
  • Make sure you have two (or three) of everything. That goes for food bowls, water bottles, huts, etc. Give them less reasons to fight.
  • Provide lots of entertainment. Distracting your piggies with toys and other enrichment activities will help them focus on something else. Just don’t let them become bored. That would be a mistake.

4. In Heat

Since Guinea pigs experience estrus cycles like humans do, they will sometimes start attacking their piggie friends.

Females go into heat every 16 days or so. Mark it on your calendar, so that you can see when this is happening and plan accordingly.

They’re very hormonal during that period and can burst into anger very quickly. This is usually followed by nipping and chasing of their cage mates.

(Pretty much the same way humans who are going through PMS!)

If you have a newly introduced cavy in the cage with the piggie that’s in heat, then chances are, the 2 guinea pigs will fight.  

On the flip side, if you have male guinea pigs around females when the females are in heat, then the male guinea pigs will start fighting each other for their female counterparts.

What To Do:

So, what can be done to contain the mayhem?

Here are few suggestions:

  • Don’t house male guinea pigs with female ones. Keep them separated in different rooms, preferably.
  • Get your female guinea pigs spayed. This procedure can be dangerous and should only be used as a last resort.
  • Try moving the female to a separate cage during this time period. Only as a last resort if the situation gets really intense. Make sure that your cavies can still see, hear, and smell each other.

You’ll have to bring female guinea pig back into the cage when she’s done going into heat or else you’ll end up with bullied guinea pigs!  

5. Old Age

There are a couple of scenarios where old age plays a part in your guinea pigs suddenly fighting – sometimes.

What usually happens is that your little friends’ old age starts a domino effect of issue that messes up the harmony of a group.

  • Cranky because they’re old. Aging can be hard on cavies, too. Joints get creaky, eyesight starts to go, body gets achy. All these factors can make a piggie grumpy and more likely to squabble with cage mates.
  • Residual hormones. Older sows can be tricky to pair, because of their long history of hormone spikes (just so you know, sows don’t go into menopause). The residual hormone can lead to hard feelings and to them suddenly fighting with their cage mates.
  • Bullied by younger cavies. This rarely happens, but it’s worth watching out for. The older piggie is bullied – usually because of hierarchy changes.

What To Do:

  • Keep a close eye on the older piggies. Make sure that you perform regular health checks. Usually weight loss is the only sign that something might be wrong with them.
  • Make sure that their environment is very comfortable. Plenty of hay and water should always be available. The cage should be enormous (or as big as you can afford). And have lots of enrichment activities and toys for your piggies to enjoy.

Frequently Asked Questions About Why Guinea Pigs Fight

What Are The Consequences Of Two Male Cavies In One Cage?

As long as they’re properly matched, there’s no reason that two males can’t be happy together in one cage. Just make sure that the cage is big enough and that there’s too of everything (e.g. bowls, toys, bed)

How Do I Know When I Should Separate My Fighting Guinea Pigs?

Usually, you only separate fighting piggies for two reasons:

  • Blood has been drawn. Because usually that means that the relationship is over and the next time they fight it might not stop at a scratch.
  • One guinea pig is bullied so much that the dominant piggie is blocking access to food. And the submissive guinea pig is losing weight.

Can Guinea Pigs Kill Each Other?

Yes, guinea pigs can kill each other. If two guinea pigs really dislike each other and neither one is backing down, then it’s possible for them to fight to the death. That’s why it’s so important to separate them if you see a flying ball of fur.

Can A Guinea Pig Live In The Same Cage As Another Animal Or Is This A Bad Idea?

Generally speaking, it’s better to keep guinea pigs groups of the same species. When animal species are mixed, there’s a chance that a bully will pick on its weaker neighbors or that diseases can spread more easily.


As you can see, there are many reasons why your guinea pigs might be fighting all of a sudden. And you have a few options to solve the problem, depending on the situation.

It can be a little tricky (to say the least) to figure out the cause of your piggies’ fights. So take a careful look at the things you did in the recent past as well as your pigs environment and they might tell you what’s going on.

And if you’re feeling overwhelmed by the fighting, don’t be afraid to ask for help. Your vet or even other guinea pig owners are always a good option and will be able to give you advice on what steps to take next.

But, if you don’t have that kind of support system, at least you now that you have the tools to help you, sit down and diagnose the situations to identify the cause of your guinea pigs fighting.

Phew, that was long!

But I hope that this article will be helpful you and that your guinea pig fighting days will be soon over (or at least whittled down to almost nothing).

Thinking about adding a piggie to your family or want to brush up on the essentials? Gotcha covered. What you need is a reliable, “all-in-one” resource to refer to when you’re struggling. A Beginner’s Ultimate Guide To Guinea Pig Care is a starting point with all the basics and more to get you on your way!

Beck, A. (2013). Guinea pigs: Keeping and caring for your pet. Enslow Pub.

Bonding. (n.d.). wheekcare. https://www.wheekcare.org/bonding

Can Guinea pigs live outside? Temperature, security and other care advice. (n.d.). Exoticdirect. https://www.exoticdirect.co.uk/news/when-can-guinea-pigs-go-outside-temperature-security-and-other-care-advice

DVM, S. L. (2015). The Guinea pig handbook. Barron’s Educational Series.

Guidelines for the Housing of Guinea Pigs in Scientific Institutions. (n.d.). CiteSeerX. https://citeseerx.ist.psu.edu/viewdoc/download?doi=

Guinea pig bonding basics. (n.d.). Animal Humane Society. https://www.animalhumanesociety.org/behavior/guinea-pig-bonding-basics

Putting Guinea pigs together. (2019, July 29). FOUR PAWS International – Animal Welfare Organisation. https://www.four-paws.org/our-stories/publications-guides/putting-guinea-pigs-together-in-a-group

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