Sexing Guinea Pigs (Guinea Pig Gender Determination).

Many owners of guinea pigs (also called cavies) find it very difficult to determine the gender or sex of their rodent pets, particularly newborn guinea pigs, and often need their veterinarian to sex their guinea pigs for them.

But sexing guinea pigs is actually easy when you know how.

This page contains everything you, the pet owner, need to know about sexing guinea pigs (guinea pig gender determination). The "how to sex guinea pigs" information provided on this page is supported by a number of helpful male and female guinea pig pictures and photos of guinea pig anatomy that clearly illustrate how to distinguish the boys from the girls. Guinea pig sexing topics are covered in the following order:

1. Some basic dos and do nots when handling and sexing guinea pigs for the first time.

2. A pictorial guide to how to sex guinea pigs - is your guinea pig male or female?

1. Some basic dos and do nots when handling and sexing guinea pigs for the first time.

There is not too much that can go wrong when attempting to determine the sex or gender of a guinea pig, so long as you are gentle, however, I will draw your attention to a couple of important guinea pig handling dos and do nots, which should be taken into consideration.

DO:

• Handle your pet guinea pigs very gently and quietly. Cavies are easily scared and will squeal and struggle when frightened (which doesn't help in trying to determine their gender).
• Hold your guinea pigs firmly around the body (chest and shoulders). Scared guinea pigs can leap out of your hands if held loosely, resulting in injury (e.g. falling off a table top). Having one person hold the guinea pig while another sexes it can be helpful.
• Perform guinea pig sexing or any guinea pig examination on the floor or on a very low table (e.g. short coffee table). This way, if the animal gets away, no injury will occur from the animal falling from a great height.
• Rest your guinea pigs on a clean towel on their backs or rumps (holding them firmly, of course) or supported firmly in your hands on their backs to examine their genitals. Guinea pig genitalia is more easily examined when the animal is sitting on its bottom or back.
• Where possible, wait until baby guinea pigs are weaned (over 3 weeks of age) before trying to determine their gender. This will avoid problems of the mother guinea pig rejecting her newborn guinea pig babies because of your smell.
• Put baby guinea pigs back with their mother immediately if they become distressed from handling.
• If you have to handle and sex newborn guinea pigs, wear disposable gloves (so you don't pass on any diseases to them) and do so in a warm area and for no more than 5 minutes at a time so that they do not get cold and distressed.
• Wear disposable gloves if handling newly-acquired guinea pigs whose background (history, where they came from and so on) is unknown, particularly if they show any signs of skin sores, hair loss (bald spots), scaly skin, respiratory disease or diarrhea or if you already have healthy guinea pigs at home. Guinea pigs can carry a range of diseases that are contagious to humans and other guinea pigs (e.g. mange, mites, ringworm, coccidia and so on) and wearing gloves will help to reduce disease transmission.

DO NOT:

• Handle guinea pigs roughly when sexing guinea pigs.
• Handle newborn guinea pigs (under 3 weeks of age) if you can avoid it. Mother guinea pigs (especially new mothers) can become uncertain of their newborn guinea pigs if you handle them too much and get your human smell all over them. This can potentially lead to the mother cavy rejecting her guinea pig babies.
• Handle young guinea pigs if they are still suckling (not yet weaned) and their mother is clearly distressed by you handling them.
• Handle newborn guinea pigs (<3 weeks old) for long periods of time. They can become cold away from the nest.
• Hold guinea pigs loosely or leave them unattended on elevated surfaces. They will dash off a high table or bench top if frightened, leading to severe injury.

2. How to sex guinea pigs - is your guinea pig male or female?

The best way to determine the sex of male and female guinea pigs is to rest the cavies on their backs or bottoms on a towel or support them cradled on their backs (held firmly in your hands at all times) and examine their genitals. There are several differences that exist between male and female guinea pigs, even newborn guineas, which you can look out for when sexing guinea pigs.



Important note - when sexing guinea pigs, only keep guinea pigs restrained on their backs for a short period of time: just long enough for you to determine their sex. Keeping cavies on their backs for too long can be distressing to them because, being a prey animal species, they will feel like they are being held down by a predator and unable to get away.



1. Examine the distance between the guinea pig's anus and its genitals (the vulva in females and the penis in males).

The penis of the male guinea pig is located much further away from the anus than the vulva of the female guinea pig is. Look at the guinea pig pictures below. These are photographs of the anuses and genitalia of two individual guinea pig adults. The first guinea pig is a young male and the second cavy is a young female. I have blown the two images up to the same size (i.e. the guinea pigs in the photos are the same size) so that comparison of this anus-to-genitals difference in distance is easier to make.


Guinea pig pictures 1 and 2: The first photo is a picture of a male guinea pig's genitalia and the second guinea pig photo is a picture of a female guinea pig's genitals. Each guinea pig has been positioned on its back to make guinea pig sexing easier to perform.

What you will notice from these two images is that the distance between the anus and the penis of the young male guinea pig (sexing guinea pigs: image 1) is a significantly greater distance than the distance between the anus and the vulva of the young female guinea pig (sexing guinea pigs: image 2). I have labeled identical images below in orange (sexing guinea pigs photos 3 and 4) to more clearly illustrate these differences in distance for you.

Author's note: The genitals of the two guinea pig sexes are much easier to recognise when you have a number of guinea pigs to compare (e.g. a litter of cavy babies, comprising both males and females) instead of just one guinea pig. Multiple guinea pigs can be seated side by side and compared directly - the significant differences in genital anatomy between the two sexes should be easy to spot.


Sexing pictures of guinea pigs 3 and 4: These are the same guinea pig photos presented before, which show the distances between the male cavy's anus and penis and the female cavy's anus and vulva respectively. These distances have been marked in orange to more clearly illustrate the differences between the two sexes.



2. Examine the shape of the guinea pig's genital opening (vulva in females and penis in males).

Look at the guinea pig pictures below. These are close-up photos of the genital regions of two individual guinea pigs. The first guinea pig is a young male and the cavy beside it is a young female. It is important to note that these guinea pigs have been photographed laying on their backs (this is why the anus is located below the genitals on each of the images).


Sexing guinea pigs photo 5: These are the genitals of a male guinea pig.
Sexing guinea pigs image 6: These are the genitals of a female guinea pig.


Guinea pig anatomy picture 7: This is the same guinea pig picture as that seen in photo 5, showing the genitalia of the male guinea pig. The anus and penis have been labeled.
Guinea pig anatomy photograph 8: This is the same guinea pig picture as that seen in photo 6, showing the genitalia of the female guinea pig. The anus and vulva have been labeled.

What you will notice from these two guinea pig photos is that the genital opening (penis or penis-sheath opening) of the young male guinea pig (guinea pig pictures 5 and 7) is shaped like a small circular dot, whereas the genital opening (vulva) of the young female guinea pig (guinea pig photos 6 and 8) is shaped like a vertical slit. I have labeled the images below (the same images as those above) to more clearly illustrate these differences for you.

Another thing to notice is the penis and prepuce of the male guinea pig, which is raised up above the level of the surrounding skin (in contrast with the female guinea pig's vulva, which is flush with the skin). The prepuce is raised and rounded like a button or dome and contains a central dot-like genital opening (the entrance to the urethra).


Sexing guinea pigs photo 9: This is a photo of the genitals of a male guinea pig (the same image as that seen in images 5 and 7). The hole in the penis (the urethral opening) has been drawn over in pink to clearly illustrate its round shape.
Sexing guinea pigs photo 10: This is a photo of the genitals of a female guinea pig (the same image as that seen in images 6 and 8). The vulval opening has been drawn over in pink to clearly illustrate its elongated, slit-like shape.

3. The female guinea pig has a distinctive "Y" shape between her anus and vulva.

Sexing guinea pigs pictures 11 and 12: These are photos of the genitals of a female guinea pig. They illustrate the distinctive "Y" shaped groove found in the perineal skin between the female guinea's anus and vulva. The "Y" has been marked in blue on image 12. This "Y" shape occurs even in very young guinea pigs (guinea pig babies) and is a useful way of sexing even very young female cavies. Male guinea pigs do not have this "Y" shape.



4. The genital region of male guinea pigs appears to bulge outwards, due to the presence of enormous testicles in the scrotum.

The scrotal sac or scrotum is a bulging out-pouching of skin that contains the testicles of male animals. In most animals, this scrotum is a distinctly obvious, bulging "bag" that is located somewhere between the anus and the penis of the male individual.

In male guinea pigs, however, the scrotum is not the bulbous "pouch of testicles" sitting just above the penis, as is seen in most other male animals. In male guinea pigs, the testicles are huge: far too big to fit comfortably into the small patch of skin located between the anus and the penis. Instead of sitting just below the anus, held within a discrete scrotal bag, the male guinea pig's testicles tend to be positioned just under the skin alongside the anus and penis unit (one testicle on each side). This lateral positioning of the enormous guinea pig testicles makes the entire genital and anal region of the male guinea pig appear to bulge outwards, as the guinea pig pictures below illustrate.


Guinea pig gender photos 13 and 14: These are photos of the genitals of a male guinea pig. The anus and penis (marked in image 14) have been indicated in previous sections on guinea pig genital anatomy, however, no mention of the guinea pig's testicles (testes) and scrotum has previously been made up until this point. Looking carefully at the images, you should notice that there are two large bulges located on either side of the guinea pig's penis/anus region (one on each side). The presence of these two bulges makes the entire genital region of the male guinea pig look as though it is bulging or protruding outwards. These bulges are the male guinea pig's equivalent of a scrotal sac (though not quite the discrete, pouchy scrotal sac seen in other male animal species): each bulge contains a large testicle. The right and left testicle regions have been indicated in blue on picture 14 of this sexing guinea pigs page.


Sexing guinea pigs picture 15: If one of the bulges lateral to (next to) the penis/anus region is grasped, it is normally possible to feel a firm, smooth testicle just under the skin. This testicle moves freely back and forth beneath the scrotal skin (it is not locked into place within the scrotal sac like that of the dog, cat and horse) and can even be retracted back into the guinea pig's abdomen at will!

Important author's note: The inability to palpate a testicle in a suspect-male guinea pig's scrotal region does not rule out that guinea pig as being a male. Guinea pigs are able to deliberately retract their testicles up into their abdominal cavity where they can not be palpated. This is particularly common when the animal is very stressed (distressed, anxious guinea pigs elevate their testicles out of harm's way) and/or if it is a young animal (baby guinea pig males are often misidentified as being females because no testicles are able to be palpated in the scrotal region). Waiting until the animal is relaxed is more guarantee of guinea pig testicles being able to be palpated when sexing guinea pigs.







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Sexing guinea pigs - Copyright June 27, 2009, Dr. O'Meara BVSc (Hon), www.pet-informed-veterinary-advice-online.com.
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