There are three ways to sex Tribolonotus. The first and most difficult of the three is on the basis of their size. Adult males tend to be larger overall than females, which generally have smaller heads and a more rounded body shape.

Pair of Tribolonotus novaeguineae

The second difference is that male Tribolonotus have small grey to blue coloured small raised pores on their third, fourth, and sometimes fifth toes on the underside of the hind legs. These may vary in colour from grey to blue. Their purpose is unclear, although it is assumed they produce a scent, maybe for territorial. These pores are absent in females.

                           

FEMALE Tribolonotus novaeguineae                                         MALE Tribolonotus novaeguineae

The third means of telling the sexes apart is by the enlarged abdominal scales which are again present in males, but not in females. There are four to six scales here in the shape of a square, located approximately where the belly button would be, which are normally a faded skin colour.

                            MALE     Tribolonotus novaeguineae                                                               MALE    Tribolonotus gracilis

Keeping tribs in pairs is your best option; single sex groups will fight very aggressively and to the death!

The key to breeding tribs is a stress-free environment, and the more settled that they are in their surroundings, then the more likely they are to breed successfully. The easiest way to achieve this is by disturbing them as little as possible and only entering the enclosure to change the water, as well as for feeding and cleaning purposes. Very little is known about the courtship behaviours of Tribolonotus. All I’ve seen a handful of times is the males approaching the female, slowly bobbing his head, expanding the dewlap of skin under the throat and then continuing to display and circle round until the female either accepts his advances, with the male biting her on the neck, or she will retreat with the male closely following behind.

Temperatures are not a great concern when breeding Tribs in captivity, because of the limited range they experience in New Guinea. What will affect them more is seasonal weather patterns. During the summer months, tropical showers arrive, and as with most reptiles, this triggers the start of their breeding cycle. As the temperatures slowly drop and the ground becomes dryer in the winter months, so egg-laying then decreases again.

Tribs become sexually mature at around three to four years old, and there are a few things to consider before deciding to commit and breed your Tribs: 

·                                 Is my skink old enough to be bred?

The easiest way to tell if a Trib is sexually mature is an orange coloured patch on the chin. In the males this will be apparent in their third year and females develop these a year later, in their fourth year, but beware, these markings will fade in and out depending on the time of year.

·               Is my skink healthy enough to be bred?

With any animal that you’re thinking of breeding, you must to consider the stress on them. Consider the following questions.

Has your skink been in any scrapes lately, has it lost toes or even its tail? Is it on the skinny side? If yes, then maybe delay breeding your Trib for the time being. Keep a record of all your Tribs’ weights and weigh them monthly. Your Tribs, both males and females, need to be at least 1.2oz (35g) to breed safely.

·               Do I have the space to house baby tribs?

Baby Tribs seem to do well housed on their own or specimens of similar size can be housed together in a small, simple set-up incorporating several hides and a shallow water source, with a close U.V.B source also being essential. I personally find moist tissue paper or coconut bark to be the best bedding at this tender age as it’s easily cleaned.

Ideally you don't want to start breeding your Tribs until they are at least four years of age. Most young females in their third year will only produce one, sometimes two clutches of infertile ova (‘slugs’) then may be a couple of fertile eggs and that's it for the year. It’s rather like a test run for the following season.

Crocodile Skinks, like 45% of the skink population, are oviparous (egg-layers), but unlike the other 95% of egg-laying skinks which lay three to six or more eggs at a time, Tribolonotus spp and Emoia spp only produce a single egg at a time. This is due to the fact that although females have two ovaries, they only have one functional oviduct, the one on the right, so it’s necessary for the left ovary to migrate across the body cavity prior to ovulation. Thus females only lay a single egg at any one time with the second egg in the clutch staying inside the female until it is laid a few days before or after the first egg has hatched. Even with this rate of egg output however, a single female can and will produce upwards of six eggs a year, adding up to three clutches. (O'Shea, Mark). 

The only exception to this rule is Tribolonotus schmidti  which is viviparous and bears a single live baby. (Dumeril and Babron)  

The soft leathery textured eggs weigh on average only 0.1oz (3g) and measure  0.8 x 0.3in (20 x 8mm) at the time of laying. Incubation takes anywhere from 65 up to 82 days. I have always removed any eggs from the parents’ enclosure. When using crickets as food for the adults, I’ve found that there are always problems with these insects eating the egg. It is well-documented that both the commonly-kept species of Tribolonotus will actively defend their clutch aggressively attacking intruders, vocalizing and refusing to move from the area the egg was laid. Try to retrieve the egg as slowly as you can therefore, and, if necessary, gently persuade the parents from the nesting site so you can collect the egg safely.

Vermiculite or sphagnum moss are ideal as an incubating medium for this type of egg, with the only difference being that they seem to do better if kept slightly more humid than say, for example, Leopard Geckos (Eublepharis macularius) around 90% is perfect. The artificial incubation temperature range for Tribolonotus eggs extends from 72°F to 80°F (22-27°C), with anything over 83°F (28°C) for a prolonged period of time most probably proving fatal for the embryo.

On the day of hatching, the youngTribolonotus will make one or two practice slits in the egg, before breaking through the leathery shell for its first breath of atmospheric air. In my experience, all this happens in no more than a few hours from the first slit to full emergence. When the babies hatch, they never have any signs of an egg sack on their umbilicus (“belly button”). Weighing in at only 0.16oz (4.5g), with an average length of 2.6in (6.5-7.5cm) how cute are these skinks?

With a keen eye they can be sexed only a few months after hatching, and as far as I’m aware, their gender is not controlled by the incubation temperature.

Lastly, please note that newly-hatched Tribs nearly always tend to play dead if approached or handled during the first month or so after hatching. After that, they are nearly always really lively, crazily quick and funnily feisty, moody and very vocal. Don’t panic if there is not much movement from them to start with, therefore.  Just keep feeding them and let them be, because they will liven up pretty soon.

Stage 1 The egg is slit in several different places.                                Stage 2 The egg is pipped, revealing the nose of the trib

Stage 3 The trib starts to wriggle its body free of the egg.    Stage 4 The trib takes its first breath of fresh air, and stumbles dizzily into the unknown!

©Dean Carguillo