How to Sex a Guinea Pig

Make sure you know the sex of your pet guinea pig. It is THE most important first step in responsible pet stewardship. Please do not assume that what you were told by the pet store, a breeder, your friend, the shelter or even the vet is right. Believe it or not, even vets sometimes get it wrong. Most vets are cat and dog vets and have little experience with rodents.

Also, I've heard many stories of people assuming that they had same sex guinea pigs because they were together for a year or more with no pregnancies. Then, lo and behold--babies!

There are too many guinea pigs in need of homes to bring more into this world. Moreover, you risk the health and even the life of a female getting pregnant at the wrong age. So, above all, make sure you know the sex of your pet.

You can even sex a new-born pup (the name for baby guinea pigs).

Difficulty: Moderately Easy

Instructions

1. 
   An adult female

   Hold your guinea pig firmly and safely, vertically so that his or her hind legs are a little open. Make sure you have ample light.

2. 
   An adult female

   Very gently try to separate the opening of their genetalia. A female will have an opening that will separate slightly into a "Y" shape. A male's parts won't separate the same way.

3. 
   Young male

   If you think it might be a male, you can confirm this in 3 ways:
   1. Testicles. If the male hasn't been neutered (the testicles are removed), they form a donut shape around the anal opening. The older the male, the more prevalent the testicles.

4. 
   Adult male

   Here is an example of an older male with much larger and more obvious testicles.

5. 
   Young neutered male

   Here is an example of a young neutered male--testicles have been removed, so the donut shape is very minimal.

6. 
   Young male (3 weeks)

   2. The BEST way to confirm a male is to get his male member to extrude. This is done by VERY GENTLY pressing just about the 'dot' area where you think it should be--right above that anal opening. Press gently with your thumb.

7. 
   Adult male

   3. Another way to confirm a male, especially in very young guinea pigs that haven't fully developed yet, is to feel for a ridge just above that area. Be gentle. It feels like cartilage just underneath the skin. In this photo of an older male, you can actually see the ridge.

Tips & Warnings

• Confirm the sex of your guinea pig at a competent guinea pig vet. Make sure the vet has guinea pig experience.
• Check out all the photos in detail on Cavy Spirit's sexing page for more visuals: www.cavyspirit.com/sexing.htm
• Baby males need to be separated from their mother at 3 weeks of age. If the male is a runt and needs more time, 4 weeks is the limit. Females can stay with their mother indefinitely, but 5 weeks is a good time before separating them.
• Nipples on guinea pigs do not mean it is a female. Males have nipples, too.
• If you suspect your guinea pig might be pregnant, be EXTREMELY careful about picking her up to try to sex her.
• Intentionally breeding pets without knowing their detailed genetic history is considered being a backyard breeder. In guinea pigs, breeding the wrong combinations can result in 'lethals'--which are white pigs with red or pink eyes who are usually blind with additional internal and especially dental deformities. See the link below. Please do not breed your pets.

Resources

• Cavy Spirit's Sexing Page
• Cavy Spirit's Social Life Page
• Guinea Pig Cages
• Guinea Pigs for ADOPTION and RESCUES
• Supplies, vets, and more for guinea pigs (BRAND NEW!)
• All about Lethal Guinea Pigs
• Breeding Guinea Pigs

[arwen1964]

on 6/30/2008 Excellent article. Glad you found the right words to get past the filtering software.