Why Do Guinea Pigs Shake Their Bums?

Both male and female guinea pigs shake their bums to show dominance. For the most part, it’s the guinea pig saying, “I’m the boss hog!”. Guinea pigs are social animals and prefer to live in groups. Group hierarchy is established by showing dominance.


Most guinea pig owners have seen it. There are cute little videos all over YouTube of guinea pigs doing it.

One of their piggies makes a little rumbling or chattering sound. Maybe another guinea pig has what they want or is getting on their nerves. Maybe there’s a newcomer to the herd.

After the rumble, the bum shaking starts. The piggie starts stomping those little back feet and being very deliberate about wiggling that backside. It’s adorable, and it’s also an important part of guinea pig communication called “rumblestrutting.”

Guinea pigs rumblestrut for a variety of reasons. It helps assert dominance over younger or smaller guinea pigs and establish a social order. If they’re female, not only will they shake their bums at each other for dominance, they’ll rumblestrut when it’s time to mate.

If aggression is boiling over, guinea pigs will rumblestrut at the start of a fight. It’s the guinea pig equivalent of the big guy at the pool table telling the obnoxious drunk, “Let’s take this outside.”

Guinea Pigs Shake Their Bums to Assert Dominance

The most common reason that guinea pigs rumblestrut is to assert dominance over other guinea pigs. Living in groups, some piggies are more dominant than others. Everyone gets along better when they know where they are in the pecking order.

Think about it; when working, it’s much easier to get the job done when everyone knows who to report to and who their subordinates are.

When a new guinea pig is introduced to an established herd, some of the herd members may rumblestrut at the newcomer. It’s just like how kids react to the new kid at school. Some are friendly right away, and some say, “You can’t sit with us.”

Even the friendly ones might let out a little bum shake at first, just to remind the newcomer whose cage they’re in now.

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If a guinea pig is bothering a more dominant one or has something they want, that dominant piggie will remind the less dominant one who’s in charge. It sounds rude, but it promotes harmony in the end. It’ll start with a rumble and a rump wiggle to say, “Get outta here, twerp!” Usually, that’s where it ends, too. The twerp leaves, the boss hog gets what they want, and nobody is hurt.

A Special Note About Females

Female guinea pigs, or sows, will rumblestrut when they’re in estrus and ready to make babies. The estrus cycle starts when a sow is approximately four weeks old and lasts 15-17 days.

While a female is only fertile for 6-11 hours during the estrus cycle, the cycle can happen any time of year. Sows are also very good about telling every boar in the area that they’re fertile and it’s time to mate.

To complicate things, neutering (the term used for removing the reproductive organs from guinea pigs) is risky for both sexes, especially females.

Giving birth is also incredibly risky for sows. If not bred at the proper time in their lives, if that first litter doesn’t arrive when the sow is around seven weeks of age, their pubic bones may knit together, preventing live birth but not preventing pregnancy.

This guarantees a poor outcome. There are ways around this, like single-sex herds or adopting neutered animals.

When to Worry

Sometimes, rumblestrutting is a sign of trouble on the horizon. If the rumblestrutting escalates to more aggressive behavior, separate the aggressive guinea pigs immediately.

That behavior can include humping or chasing. Confusingly, those are also play behaviors. If the play doesn’t seem to be reciprocal, if one piggie seems to do all the chasing and humping and rumblestrutting, start paying attention. Once a guinea pig opens their mouth to bare its teeth, chattering, and lunging, playtime is over.

If your guinea pigs get aggressive toward each other, either separate the guinea pigs with a dustpan or cookie sheet (or other flat, sturdy item) or reach in with a thick glove and grab one. Do not reach in with bare hands. Each fighting guinea pig will be determined to send their opponent and everything in their way to either the Emergency Room or the Great Beyond. This includes well-meaning human referees.

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Bum Shaking is Important

Rumblestrutting is an important form of guinea pig communication. In most cases, it establishes dominance. It’s a way for a bigger, more established, or more dominant guinea pig to show their juniors what’s what.

Occasionally, a junior piggie will rumblestrut to a dominant guinea pig to check their place in the pecking order, which they’ll quickly learn.

When a sow rumblestruts, she may be in estrus. Since breeding guinea pigs is generally a bad idea, guinea pigs should live in single-sex herds or be neutered.

Neutering a guinea pig carries higher risks than neutering other animals, though, so a thorough assessment of the risks and benefits of neutering with an exotic vet is absolutely necessary.

The only time to worry is if the piggies show actual aggression. Guinea pigs are social animals and usually get along well. Sometimes, though, little dominance spats turn into full-blown fights. If that happens, for the piggies’ safety and the human’s, it’s important to separate the guinea pigs quickly and safely.

Use a dustpan, baking sheet, or other rigid, flat item to stop the fight, then reach in with a gloved hand to grab one of the fighters. Again, do not reach in barehanded; guinea pigs have powerful jaws and aren’t afraid to use them.

Because of the danger inherent in fighting, rumblestrutting is usually used in place of a confrontation. It’s a fascinating look into guinea pig communication, and just so cute to watch.

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