How to Tell if Your Guinea Pig is Male of Female

My children love animals, so we have a lot of pets, including seven guinea pigs. Many unsuspecting and responsible people have brought home two guinea pigs and housed them together with the intention that they’d keep each other company. Before long, baby guinea pigs arrive, usually not long after you’ve been told that you purchased two animals of the same sex. It happens, mostly because the people at the pet store didn’t sex the animals properly, or didn’t sex them at all and are simply guessing.

To prevent this from happening, you should learn how to sex guinea pigs yourself. This is also an important skill to acquire if you wish to breed your guinea pigs to avoid getting home with two females or two males. But it's equally important just because your kids are going to want an answer when they ask, "Is it a boy or a girl?". If you can sex guinea pigs yourself, you can be assured of getting exactly what you ask for. You can also answer your children truthfully.

It is not easy to sex young guinea pigs. Their genitalia is not yet fully formed and so is difficult to locate. Mistakes are always possible, though regrettable. Most pet stores will tell you of the “y” and “i” method of sexing, but since guinea pigs should be sexed at 2 weeks old, this method isn’t infallible. There are other ways to tell, and once you know what you’re looking for, sexing a young guinea pig becomes quite easy.

Sexing Female Guinea Pigs

Many times, pet stores will assume that a guinea pig is male because it has bumpy genitalia. This is not the case. Female guinea pigs have bumpy genitalia, so roll your guinea pig on its back to look closely at the genitalia. Run your fingers over the area and look for a “y” formation. This usually indicates a female. To be sure, press on the “y” gently. It should open up just a little. If it doesn’t, you might be holding on to a male guinea pig.

Sexing Male Guinea Pigs

Male guinea pigs have genitalia that is almost shaped like an “i”. There will be a vertical line with a dot. That dot is the penis. There may also be a small bulge, though this often isn’t visible in a guinea pig as young as 2 weeks old. If you don’t notice the “i”, then turn the guinea pig over on its back. Press gently on the stomach just above the genitalia. This should cause the penis to protrude, if the guinea pig is indeed a male. No penis should indicate a female guinea pig.

It is important to know what gender your guinea pigs are. If you’re breeding them, you’ll want to sex the newborns quickly, as young males should be removed from their mother and sisters before 4 weeks of age to prevent inbreeding. If you don’t want to breed, but you do want to house two guinea pigs together, your ability to sex your own guinea pigs is even more important. If you’re ever in doubt, you should take your guinea pigs to a qualified small animal veterinarian. He or she should be able to determine the sex for you with very little effort.