In lizards and snakes the males have two penises, which are known as hemipenes. (Turtles and tortoises have lost the plot and only have one — like the monkeys and naked apes and such.) The Squamata, the order comprising snakes, lizards and amphisbaenians, wisely keep their hemipenes in an internal pocket when not in use. The hemipenes are arranged side by side behind the cloaca. During copulation one hemipene is everted, ideally the one best aligned with the female’s cloaca for successful intromission.
If the species has only minor sexual dimorphism, it can be difficult to easily sex juveniles and adults visually. The genus Tiliqua shows limited sexual differences and with the hemipenes tucked away in hiding, it is fairly tricky to tell them apart. One helpful sign to look for is that young male bluetongues will sometimes evert both hemipenes to produce ‘sperm plugs’. Most likely this is a way of clearing out the hemipenes of blockages of dead skin, cells and sperm. If you discover two small white gelatinous ‘packets’ on the cage floor or in the water bowl, this will certainly indicate a male. Absence does not prove the skink is a female, however, as these ‘packets’ can easily go unobserved.
Males and females can breed at the age of 18-months if they have grown to appropriate adult sizes.I keep all the adults separate and introduce them in a large ‘neutral’ area when it comes time to breed them. In the wild, females would normally stay close to their own territory while males would wander about, trying to find receptive females and avoid other combative males. Males are EXTREMELY aggressive during breeding season, and are capable of inflicting serious damage on other males (or your thumb if it gets in the way). I have one female that will only breed in her own tank and will not breed in a neutral tank. She simply runs and/or violently resists sexually active males. In her own territory, however, she will accept being bred.
Males grab onto the skin of the shoulder of the female, ‘encourage’ the female to lift her tail, and then loop their body under hers. Everting the left hemipene in the example below, the male is able to copulate. Copulation lasts a minute or two, during which time the male ejaculates. After ejaculation the male releases the female and slowly withdraws the hemipene back into its pocket.
In this second pairing, a fair amount of the seminal fluid and sperm has ended up on the towel. Obviously, not a good place for it to end up if fertility and babies are the target!
Also, there’s some blood in the ejaculate, giving it a reddish hue. This is not uncommon but obviously causes some concern. I try to breed my skinks on towels rather than any kind of normal substrate. It’s easier to see what is going on, and also allows the male to slowly retract his hemipene– they often drag it around for awhile in a bit of a daze — without picking up debris such as dirt, wood chips, gravel, sand, splinters, etc. I suppose they get by without towels in the wild but seems like a good precaution.
On two occasions I’ve had males seriously hemorrhage blood from their hemipene during copulation! A lot of blood! Apparently, they can rupture a blood vessel while the hemipene is erect and engorged with blood. This is really disconcerting to witness (maybe more for a male viewer) because it seems like a huge amount of blood coming out of a relatively small animal with his relatively small hemipene.
Here’s a patch of blood shown in the photo below but the large towel was liberally spattered with blood. During bleeding the males did not seem in pain or distressed. After the hemipene was retracted, the bleeding stopped and the males did not seem to suffer any additional problems. However, in both cases I retired the male for the breeding season. The first time it happened I retired the male permanently and found him a good home as a pet — not to be used as a breeder. On this second occasion in February 2021, I will try the male again as a breeder in 2022, and hope everything has healed and there are no additional problems.
All of this has been about the sex life of the male skink. What about the role of the female blue-tongue skink? As an observer, it does not seem to be a particularly transcendental experience for them. If they are receptive, they will sometimes make a submissive gesture to the male by slowly lowering the head and/or slowly wiggling the end of the tail. Or they remain passive while the male proceeds to charge at them, aggressively biting and ‘grabbing’ them by the shoulder. Once in a position to copulate, the males often repeatedly stroke the female’s back with one of their back legs and toes; this seems to ‘stimulate’ the female to lift her tail so the male can slide his tail under hers and get into the final position to initiate copulation. (Maybe female skinks are heavily into back rugs and this is their favorite part of the whole encounter.)
Adept males quickly get a good grip on the shoulder and get on with it. Clumsy males will often chew the female’s shoulders repeatedly or even bite her head or legs. This can cause damage, and I often remove males if they appear to be harming a female without making much progress toward a successful copulation.
If females are not receptive they will sometimes race to escape — or even attack the male. Females seem to accept being bred two or three times at most. I prefer to space the breedings 2 or 3 days apart. I never expect a female to “endure” more than three breedings as they often change their behavior radically: when on the first breeding they appeared calm and receptive, by the third breeding they may become extremely nervous and flee, or answer male sexual aggression with defensive aggression. Enough is enough! –appears to be the motto of the female.
I always carefully observe the breeding encounters of my Northern BTs, and I am always there to break things up if it goes awry. My main focus is to make sure no one is injured. I usually separate the male and female fairly soon after a successful copulation.