The Ultimate Guide on How to Determine a Guinea Pig’s Gender

I recently discovered a foolproof way to determine a guinea pig’s gender, and let me tell you, it’s been a game-changer! For all those guinea pig owners out there who have wrestled with the age-old question of whether their furry friend is a boy or a girl, I am here to put your minds at ease. In this ultimate guide, I will walk you through the simple yet effective methods to accurately determine a guinea pig’s gender, saving you from any potential confusion or mishaps. So, if you’re ready to have some fun and learn some fascinating facts about these adorable creatures, let’s get started!

The Ultimate Guide on How to Determine a Guinea Pig’s Gender

Hey there! Have you ever wondered how to tell the gender of a guinea pig? Well, look no further! In this comprehensive guide, I’ll walk you through everything you need to know about determining the gender of these adorable furry creatures. From their physical characteristics to their behavioral differences, we’ll cover it all. So, sit back, relax, and let’s dive into the world of guinea pig gender determination!

Physical Characteristics


When it comes to guinea pig gender determination, size can actually play a role. Typically, male guinea pigs tend to be slightly larger than females. However, it’s important to note that size alone isn’t a foolproof method for determining gender, as individual variations and genetic factors can also contribute to differences in size.

Body Shape

Looking at the body shape of a guinea pig can also provide clues about their gender. Generally, males have a more muscular and solid build, with broader shoulders and a wider overall frame. On the other hand, females tend to have a slightly more streamlined and slender body shape.

Head Shape

While it may not be the most obvious characteristic to look for, the shape of a guinea pig’s head can sometimes provide some insight into their gender. Male guinea pigs often have a more pronounced and angular head shape, with a broader forehead and a stronger jawline. Females, on the other hand, may have a more rounded and petite head shape.


Of course, one of the most reliable ways to determine a guinea pig’s gender is by examining their genitalia. Males have a small, prominent genital bulb located just behind the umbilical region, which is the opening of the urethra. Females, on the other hand, have a Y-shaped genital opening situated closer to the anus. Taking a close look at these areas can help in accurately identifying the gender of your guinea pig.

Behavioral Differences


Observing the behavior of your guinea pigs can also provide some hints about their gender. Male guinea pigs tend to display more dominant behavior, such as mounting other guinea pigs and marking their territory. Females, on the other hand, generally exhibit more submissive behavior.

Territorial Marking

Male guinea pigs have a unique tendency to mark their territory by spraying urine in a backward motion. This behavior is called “scent marking.” If you notice your guinea pig engaging in this territorial behavior, chances are you’re dealing with a male. Female guinea pigs typically don’t exhibit this marking behavior to the same extent.

Mounting Behavior

Mounting behavior is another behavioral difference that can be observed between male and female guinea pigs. Male guinea pigs often display mounting behavior as an act of dominance. It’s their way of asserting themselves in the social hierarchy. Female guinea pigs, on the other hand, typically don’t engage in mounting behavior.

Age Considerations

Determining the gender of a guinea pig can be influenced by their age as well. Let’s take a closer look at how the different age groups can impact gender determination.

Newborns (Under 1 Week)

Determining the gender of newborn guinea pigs can be challenging since their genitalia are not fully developed yet. It’s best to wait until they are at least one week old to have a better chance of accurately determining their gender.

Young (1-4 Weeks)

At around one to four weeks old, guinea pigs start to display more noticeable genitalia. This is a good time to start observing their physical characteristics and behavior to determine their gender. However, it’s still important to be cautious as their genitalia may not be fully developed or easily distinguishable.

Juveniles (4-10 Weeks)

As guinea pigs enter the juvenile stage, their genitalia become more distinct and easier to identify. This is a reliable age range to determine their gender since their reproductive organs are more developed.

Adults (10 Weeks and Older)

By the time guinea pigs reach the age of 10 weeks and older, their reproductive organs are fully developed, making it easier to determine their gender accurately. At this stage, the physical characteristics and behavior are more indicative of the guinea pig’s gender.

Visual Gender Determination

Anogenital Distance

One method of visually determining a guinea pig’s gender is by examining their anogenital distance. In males, the anus and genital opening are closer together, creating a shorter anogenital distance. In females, the anus and the genital opening are further apart, resulting in a longer anogenital distance.

Shape of Genital Opening

Another visual clue to consider is the shape of the genital opening. In males, the genital opening appears to be more circular or round, while in females, it forms a Y-shape. This distinction can help in confirming the gender of your guinea pig.

Sexing by Hair Patterns

In some cases, hair patterns can provide hints regarding a guinea pig’s gender. Some male guinea pigs may have a “boar swirl,” which is a cowlick-like pattern occurring on their lower back area. This swirl is more common in males and can serve as an additional clue in determining their gender.

Manual Gender Determination

Gently Lifting the Guinea Pig

One way to manually determine a guinea pig’s gender is by gently lifting them and inspecting their genital area. Be sure to support your guinea pig properly and handle them with care throughout the process. By exposing their genitalia, you can make a visual analysis to ascertain their gender.

Pressure on Genital Area

Applying gentle pressure to the genital area can also provide some clues about a guinea pig’s gender. Males may show the intromittent organ, which is a small penis-like structure, when pressure is applied. Females, on the other hand, won’t display this organ, further confirming their gender.

Vent Sexing

Vent Anatomy

Vent sexing is a method used by experts to determine the gender of guinea pigs. It involves examining the vent anatomy, which is the opening that connects the digestive and reproductive systems. This method requires precision and experience to accurately determine the gender.


During vent sexing, a small probe is gently inserted into the vent of the guinea pig to feel for reproductive structures. The presence or absence of these structures helps to identify the gender. Vent sexing should only be performed by trained professionals or experienced individuals to avoid causing harm or discomfort to the guinea pig.

Consulting a Veterinarian

Professional Expertise

If you’re unsure about determining the gender of your guinea pig or have difficulty doing so yourself, it’s always best to consult a veterinarian. Veterinarians have the expertise and experience to accurately determine a guinea pig’s gender and can provide guidance and advice based on their professional knowledge.

Genetic Testing

In some cases, to determine the gender of a guinea pig accurately, genetic testing may be needed. This involves sending a DNA sample to a laboratory where it will be analyzed to determine the guinea pig’s gender by examining its chromosomes. Genetic testing is a highly accurate method and can provide definitive answers when other methods are inconclusive.

Identifying Male Guinea Pigs

External Genitalia

Male guinea pigs have external genitalia in the form of a small, prominent genital bulb located just behind the umbilical region. This bulb represents the opening of the urethra and is a key characteristic to look for when identifying males.

Scent Glands

Another indicator of a male guinea pig is the presence of scent glands. Male guinea pigs have scent glands located on their lower back around the anal area. These scent glands produce a strong scent that is used for marking territory and identifying themselves to other guinea pigs.

Testicle Palpation

Palpating a male guinea pig’s scrotal area can also help determine its gender. Males have two small, movable testicles located just above the genital bulb. By gently feeling the scrotal area, you can confirm the presence of testicles, which is a clear indication of a male guinea pig.

Identifying Female Guinea Pigs

External Genitalia

Female guinea pigs have external genitalia in the form of a Y-shaped genital opening situated closer to the anus. This opening is more rounded and wider than that of a male guinea pig. Examining the external genitalia can provide a definitive clue in identifying females.

Vulva and Urogenital Opening

Another distinguishing feature in female guinea pigs is the vulva and urogenital opening. Females have a more prominent vulva, which appears as a small vent located just below the anus. This prominent vulva and the wider urogenital opening clearly distinguish females from males.

Palpation of Ovaries

For a more accurate determination of a female guinea pig’s gender, palpating the ovarian area can provide additional confirmation. By gently feeling the lower abdomen, you may be able to detect the presence of small, soft ovoid structures, which are the ovaries and are exclusive to female guinea pigs.

Common Misconceptions

Color or Coat Type

Contrary to popular belief, a guinea pig’s color or coat type alone cannot reliably determine its gender. While certain color patterns or coat types may be more common in one gender than the other, it is not a definitive indicator of a guinea pig’s gender. It’s always best to rely on other physical characteristics and behavioral differences to accurately determine gender.

Behavioral Traits

While guinea pigs do exhibit behavioral differences based on their gender, it is important to note that these differences are not foolproof indicators of gender. Some male guinea pigs might display more submissive behavior, while some female guinea pigs may exhibit mounting behavior. Although behavioral traits can provide some clues, they should not be solely relied upon for gender determination.

And there you have it, a comprehensive guide on how to determine a guinea pig’s gender! By observing their physical characteristics, behavioral differences, and utilizing various methods such as visual determination, manual gender determination, and vent sexing, you’ll be able to confidently identify the gender of your furry friend. Remember, when in doubt, always consult a veterinarian who can provide professional insight and guidance. Happy gender determining!





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