Blue-tongue skinks are cute, little lovable animals, however they are also incredibly difficult to sex. There are multiple methods to determine their gender, but not all of them are reliable or all that useful.
By far the best methods to sex a Blue-Tongue Skink are firstly observing them mount a female, or seeing if they have hemipenes, or observing them drop seminal plugs.
Blue-tongues display very little sexual dimorphism. Sexual dimorphism basically are traits and characteristics that can differentiate the genders of an animal species.
For instance, in humans, sexual dimorphism would be displayed visually by things such as the genitals, breasts, muscle-mass, height and a slew of other traits.
In skinks, these differences are much, much less pronounced.
I’ll give you an example. You may have read somewhere that you can often tell the difference between a male and female blue-tongue by comparing their head sizes, as males are supposed to have larger heads than females. But, just about every owner who has bred skinks can attest that this isn’t a foolproof method. Many owners have incorrectly determined the sex of their skink based on this, only to find out later they were wrong.
Another common method is to look at their eyes; the eyes of male skinks are supposedly more brightly coloured versus those of females, which tend to be a bit duller, dimmer and darker in colour. Again, this method is just not fool-proof, as I have personally seen female skinks with very vibrant, colourful eyes.
Moreover, both of these methods also fail on another useful metric, they are incredibly difficult to actually work out in the real world. Very few people are really knowledgable about blue-tongues, and unless you have been around them for a while, and seen more than your fair share, you will probably not be able to accurately estimate what exactly constitutes a “larger head” and “more brightly coloured eyes” than not.
Now, that being said, there are 3 methods in my opinion that are much more reliable than the above common methods. There are unfortunately, a few limitations with all 3 of these.
99.9% Surefire Method – If a Skink has Hemipenes, it’s a Male
This method will take a little bit of work, and at first glance may seem a bit scary, but it’s perfectly safe. Basically, you will try to “pop” your skink’s hemipenes out.
Hemipenes are the paired reproductive organs that sit “inside” the skink’s body, right above the tail, but on the bottom side of the skink (so if you flipped your skink over onto its back, these would be right above the tail).
Now, you can’t see them when they are closed, hence why you need to “pop” them.
All you do is flip over your skink while still holding him or her in your arms, take your thumb and find the cloaca. The cloaca is basically your skink’s “butt” for lack of a better word. Once you have found the cloaca, take your thumb, lay it right above the cloaca and roll your thumb upwards and to either side, while exerting a little bit of pressure.
If the skink is a male, one of the hemipenes should “pop” open. If this happens, congratulations you have now definitively sexed your skink!
If nothing “popped” it’s most likely a female.
I say “most likely” because this method isn’t fool-proof. Getting some skinks’ hemipenes to “pop” can prove to be quite difficult.
And, perhaps most importantly, you cannot use this sexing method on young skinks or small skinks, as you may cause them damage.
If you have done it properly, it won’t hurt your skink and the hemipenes will contract back into the skin fold.
I know that figuring out how to do this from reading text isn’t exactly easy, so I would highly advise you to watch the video below on how to do this properly, and if you are serious about using this particular method.
99.9% Surefire Method #2 – Seminal Plugs
Google a picture of these. If you see these laying around your skink’s habitat, he is almost assuredly a male. Males will eject these around their habitats during breeding season.
These are approximately 1-inch white or grey gobs of built-up semen that males need to eject in order to “clean out” their reproductive system. During the breeding season, a male will often eject a seminal plug every single day.
This method however, will only work on mature male skinks. Likewise, if you have more than 1 skink in the same cage, it may be unreliable if you don’t actually see which skink ejects the plug.
99.9% Surefire Method #3 – Mounting
This is the last reliable method to sex your skink. Mounting is just as its name suggests. During mating, males will climb on top of and “mount” females for reproduction.
If you observe a skink perform this behavior, it is almost assuredly a male.
There are lots of limitations with this method however, as you will need at least 2 skinks, 1 male and 1 female, for it to work.
Moreover, because males are often territorial and aggressive towards each other, if you unknowingly put 2 male skinks in the same cage, they may fight.
And that is really the problem with all of these methods, they all have limitations, such as only being able to observe seminal plugs during breeding season and with a mature skink, likewise, also needing an older, bigger skink by checking for its hemipenes.
However, unless you are a breeder, not knowing the sex of your skink, at least temporarily, is not at all going to hinder you from providing a good, safe environment for him or her to grow up in.
My advice would be, if you don’t know the gender of your animal, to be patient, particularly if your skink is still young, and look for the cues listed above when he or she gets older. You could also make a guess based on his or her head size, and his or her eye color, but it’s not accurate.
So, to sum up, the best, most reliable methods to sexing a blue-tongue skink are:
- checking for hemipenes
- observing ejected seminal plugs
- observing the skink mount another skink