how to determine the gender of a blue tongue skinks - visual clues and surefire methods

How To Tell If a Blue Tongue Skink Is a Male or Female?

Most blue tongue skink owners want to find out the gender/sex of their blue tongue lizard. You might need to know blue tongue skink’s gender for breeding purposes, but it’s also interesting to know your pet’s gender in general. In this post, you will learn the ways to help you find out your blue tongue skink’s gender/sex. Sexing blue tongue skinks can be hard, so you will need to look for many factors.

To determine the gender your blue tongue skink, look at these factors:

  • Body length – females are usually longer than males.
  • Head shape and size – males usually have larger and broader heads, but it’s not always true. If the head is wider than the body, it’s likely to be a male. Some males might have smaller heads, due to a bad diet during its baby years. What is more, some species have large heads from the birth, such as Shinglebacks.
  • Weight – males are generally heavier than females but this can be different. Everything will depend on the diet and general health.
  • Body shape – males are often broad and females are often round around the hips.
  • Tail – males have hemipenes (reproductive organs) at the base of the tail. This often creates a bulk at the base of the tail. There might be a bulk to the left and right side, where the hemipenes lay. But the female can have a fat tail, which might make you think it’s a male. Blue tongue skinks store fat in their tails.
  • Reproductive organs – can be seen through ‘popping’.
  • Breeding behaviors – surefire way to determine the gender.
  • Everting hemipenes when pooping – a male can evert its hemipenes when its pooping.
  • Semen and seminal plugs in the excrement – surefire way to tell your skink is a male. See picture below.

It can be very hard to determine blue tongue skink’s gender/sex by inspecting the lizard visually. All of the visual factors are only clues, and should not be relied on when finding out the gender. This is especially true when blue tongue skinks are still young – less than 12 months old. There is almost no difference between female and male blue tongue skink characters and temperaments (apart from breeding behaviors).

When looking at the head shape, body size and length, you will need to compare at least few blue tongue skink to make any conclusions. So, visual inspection isn’t the most reliable way to find out the blue tongue skink’s gender. So, don’t make conclusions of your blue tongue’s gender by body shape, size and markings.

The most reliable and surefire ways to tell the blue tongue skink’s gender is to:

  • Evert (pop out) male’s hemipenes (male’s reproductive organs) – not the most comfortable and safe way.
  • Performing an X-Ray/Ultrasound at the vet – X-Ray uses radiation and sometimes contrast dyes
  • Observe the breeding behaviors
  • See your blue tongue’s hemipenes when he is pooping
  • Search for seminal plugs or fresh semen around the tank.

‘Popping’ blue tongue skink’s hemipenes to determine the gender

‘Popping’ blue tongue skink’s hemipenes can help you determine the sex of your lizard. Please note that this method is not very accurate and can lead to injury and damage. Some people might claim that they’re experts at this, but in reality give you false results.

To pop out, or evert blue tongue skink’s hemipenes, you will need to hold the skink with its belly turned to you. Then, you will need to put the thumb under the vent and start pushing the thumb up, applying some force. Hemipenes might pop out. Another method is to open the flap, and push your thumb directly inside the vent, trying to pop out the hemipenes.

It’s always better to perform popping with younger blue tongue skinks. This is because adults have large hemipenes, and it can be hard to evert them. Applying too much pressure can cause injury and damage to hemipenes. It’s better not to perform popping and rely on other methods instead.

Performing a contrast X-Ray/Ultrasound to determine blue tongue skink’s gender

Sometimes you can perform a contrast X-Ray to see your skink’s gender. The vet will inject a contrast dye in blue tongue skink’s vent, and then take X-Ray scans. Then, he/she will inspect the scans to see if there are any hemipenes. X-Ray scanning uses radiation, so it’s not recommended.

The vet might also perform an ultrasound of a sexually mature female to see if he has any follicles. This method will be only suitable for sexually mature females, that are often 2 years old and over.

Breeding behaviors in blue tongue skinks to determine the gender

During the breeding season, male’s hemipenes tend to swell. But an absolutely surefire way to determine the gender of your skink is to observe the breeding behaviors. To find out your blue tongue’s gender this way, you will need few skinks. Please put two skinks together to observe breeding behaviors when they are at least 8-12 months old. Otherwise, they will be too young to show any breeding interest.

If you place two males together, you will see how they become defensive and territorial. Males will start hissing, biting, moving sideways to look bigger. They are very likely to fight and bite each other.

If you place a male and female together, you will see how male approaches the female. It might not happen straight away, and he is likely to stare at her for a minute. Then, he will approach her quickly and bite her on the side to hold her in place. She won’t be biting back or resisting too much. After some time, he will position his body on top of hers, brushing his tail and hind legs on her. If the female is receptive, she will whip and lift her tail slightly and they will start mating. Please note that male will leave bite marks and even wounds on the female, and this is normal.

blue tongue skink mating - breeding behaviors to determine the gender

But please note, that sometimes a male might be very desperate and try to mate with another male. Just observe the behavior and see if the bitten skink is lifting the tail and being receptive.

If you place two females together, they will either become slightly defensive or will ignore each other. There is a chance that the females will bite each other slightly, move around, but it should be less serious than in males.

What is more, some owners believe that male’s neck (from inside) turns slightly pink during the breeding season, when he is ready to mate. This might not be accurate, and is just another observation.

female vs. male blue tongue skink - how to determine the gender

Seeing your blue tongue’s hemipenes when he is pooping

Another surefire way to determine the gender of your blue tongue skink is to watch its excrement. Sometimes, males might evert their hemipenes when pooping and you will be able to see them. You might start seeing hemipenes at the age of around 5 months.

In this 9 second video, you can see male’s hemipenes when he is defecating.

Searching for seminal plugs or fresh semen around the tank

Presence of fresh semen or seminal plugs inside the tank will tell you that your blue tongue is a male. Seminal plugs look like white plugs, or strands that are dried sperm. Your blue tongue skink will release seminal plugs if he’s a male, and you will need to find them. Sometimes, they might get lost in the tank, especially if you are using loose substrate. If you want to search for seminal plugs, use reptile carpet, newspaper or towels. You might start seeing seminal plugs when your blue tongue skink turns 6-10 months old, and of course if he’s a male.

How To Tell If a Blue Tongue Skink Is a Male or Female - finding out blue tongue's sex - seminal plug

Be extra attentive when examining seminal plugs or fresh semen. Seminal plugs might look like urates. Urates are semi-solid urine salts that reptiles produce instead of liquid urine to minimize water loss. Urates are often brighter in color than semen.

Thank you for reading this article. To learn more on care, click here to find blue tongue care sheets.