How to Tell Your Guinea Pig’s Gender (With Photos)

It can be challenging to distinguish between male and female guinea pigs to the untrained eye, especially when your piggy is still a baby. However, there are some discernable differences both in appearance and behavior to help you tell whether your guinea pig is a boy or a girl.

Below I have a collection of photos of my own piggies, both male and female at different ages and colors to help you determine the sex of your own guinea pigs at home.

Mis-sexing guinea pigs, especially babies, is very common in pet stores, individuals rehoming their pets, and even rescues on occasion. Anytime you get a new guinea pig, it’s a good idea to confirm the gender before bonding them with any other guinea pigs to avoid accidental litters and pregnancy complications in older guinea pigs.

Guinea Pig Gender Photos

Below are photos of some of my guinea pigs at different age stages. I’ll label each photo in the captions underneath.

Physical Differences Between Male and Female Guinea Pigs

As you can see in the photos above, there are a few discernable differences between males and females. As a general rule, males typically have what appears to be an i shape, whereas females have a V shape in their genital area.

However, girls often have a small pimple-type dot as well, which can throw people off. Sometimes boys have a U-type shape around their penis, which can also add confusion. However, the dot is much more pronounced on males, and the V is much more obvious on females.

Both male and female guinea pigs have nipples, so this is not a factor in determining gender.

Males typically grow slightly larger than females as adults. However, this is NOT an accurate method of sexing them. For example, here are the genders and weights of some of my piggies, past and present:

Males:

• Ace – Male Abyssinian – 1020 grams
• Ceico – Male American – 1077 grams
• TJ – Male American – 1190 grams

Females:

• Willow – Female American – 1089 grams
• Daisy – Female American – 1049 grams
• Peach – Female Peruvian Cross – 1134 grams
• Poppy – Female Abyssinian – 950 grams
• Pansy – Female Peruvian Cross – 1150 grams
• Skylar – Female Abyssinian – 1121 grams
• Skittles – Female Abyssinian – 1040 grams

Physical Test

Another way you can determine gender is with a hands-on test.

With girls, their genital area is often less noticeable until the area is spread apart, especially in younger guinea pigs. I’ll show you what I mean in the photos below.

To conduct this simple test, place your finger and thumb on either side of the genitals and gently spread the area from side to side. If a V shape appears, you have a girl! Boys do not really look any different when you do this.

However, there is another test you can conduct for the boys. Simply press gently above the dot in their genital area. If the dot pops out a little bit further, you have a boy! Doing this with a female should not produce a noticeable difference.

Adult male guinea pigs will also have noticeable testicles. These are visible below the bum area. You can also usually see them from behind when your guinea pig is standing. You can typically see these without even picking up your guinea pig. Some males will have larger testicles than others.

You may also see a swollen-looking area around the genitalia before they fully drop. Male guinea pigs usually drop around 4-6 months old, depending on the guinea pig.

A neutered male’s genital area will look the same as an intact male, minus the testicles. Neutered males look more like younger males that have not dropped yet.

Spayed females do not look any different from the outside than unspayed females.

Some guinea pigs are a little more difficult to determine the gender of than others. Babies can be a little challenging, but usually, by 2-3 weeks old they can be sexed pretty accurately. Long hair or dark-colored guinea pigs can also be harder to see in some cases. It’s a good idea to ensure you have good lighting when trying to determine gender.

Sometimes taking photos can help so you can study them after without trying to wrangle a squirming piggy for too long. If your guinea pig is extremely wriggly, it can help to have a second person; one to hold, and one to take photos or determine the gender. You can also try distracting your guinea pig with some veggie treats if that works.

Sexing Baby Guinea Pigs

If your guinea pig has a litter of pups, it’s important to sex them and separate boys from the mom and sisters at 3 weeks old. Guinea pigs are born nearly fully developed and they don’t take long to reach sexual maturity. Males have been known to impregnate other guinea pigs as early as 3 weeks of age. Females usually have their first heat between 4-6 weeks old.

It can be quite difficult to tell the gender of a newborn guinea pig, but the differences become clearer by 2-3 weeks old. Although the males must be physically separated from their mom at 3 weeks old, they are not fully socialized or emotionally independent by this age.

Therefore, it’s best if they can be housed with other males, either their brothers, dad, or another adult male so they get that socialization and interaction from other guinea pigs. Females should stay with their mom until 6-8 weeks of age.

Behavioral Differences in Male and Female Guinea Pigs

Males and females do have behavioral differences that apply to the vast majority of guinea pigs. However, behavior should never be used as a main factor in determining the sex of your guinea pig. It should be used as an additional measure once you have relied first on the physical differences.

You will always find more confident females and less confident males that don’t fit these norms to a tee, so use everything here as a guideline, not a rule. Nonetheless, I’ve had seven males and twelve females and this is what I’ve noticed as behavioral differences between the genders.

Spraying Pee

First of all, both male and female guinea pigs will spray pee. However, males spray from underneath, so you may see them lift their leg and shoot sideways. Girls, on the other hand, shoot pee straight out the back. You are unlikely to see babies spraying pee, but adults will usually do it from time to time, some more than others.

Females are more likely to spray pee if another guinea pig comes too close behind them or tries to hump them. When girls come into heat, they may try to chase and hump their cagemates, so this is when you’ll commonly see the other girls spraying pee at the instigator. Males can be more territorial, so they’ll often spray pee as they walk by another guinea pig, especially after rumble strutting around and purring.

Rumble Strutting and Purring

As a general rule, males usually purr and rumble strut more than females. They will do it towards all other guinea pigs, male and female. Females will absolutely purr and rumble strut as well, but the boys are on another level. However, if you only have one gender of piggies, it can be hard to tell how much is a lot without comparing both genders.

Girls usually only purr and rumble strut when they meet new guinea pigs or when they are in heat, which lasts for a day or two every two weeks. Males will often purr and rumble strut at every opportunity.

Humping is generally the same. Males are much more interested in trying to hump other guinea pigs, while females only do when in heat or during introductions with new guinea pigs.

It is even less common for baby females to purr and rumble strut a lot. My one little baby girl only purred for the first time at 4 weeks old, and just that one day (presumably her first heat.) So if you have a baby that starts this behavior early, there’s a good chance you have a boy on your hands!

Getting a Second Opinion

If you have any doubt as to the gender of your guinea pig, you should find other experienced individuals to help you out. One way is to post some clear photos in good lighting in a guinea pig Facebook group. Choose a group that has a dedicated group of admins that are experienced in sexing. These groups usually close comments to general members that could be guessing, and make sure you get a response from an experienced admin only.

You can also take your guinea pig to the vet for confirmation. However, you’ll want to find a clinic that works with exotics and call ahead to ensure that there is someone that is experienced in sexing guinea pigs. Not all vets are trained specifically on that, so you’ll want to make sure they can give you an accurate confirmation.

In Conclusion

Determining the gender of your guinea pig can be tricky, especially if you have young, squirmy babies on your hands. I was in the same situation after adopting a misgendered pair with a pregnant female, so I know how overwhelming it can be! However, I hope this guide was able to help you out! If you’re not 100% sure about your guinea pig’s gender, a visit to a qualified exotic vet is always a good idea.