10 Cool Facts About Red-Eyed Crocodile Skinks

Only some of the fascinating facts about red-eyed crocodile skinks (Tribolonotus gracilis) are revealed by their name. From their striking red eye-rings to surprising survival tactics, we explore 10 cool facts you may not have known about these elusive and fascinating creatures.

1. Dragon-like Armour for Survival  

Red-eyed crocodile skinks are clad in striking four ridged dorsal rows of large, keeled scales  plus ossified head plates. These scales, known as osteoderms, are very similar to crocodile osteoderms giving them a miniature crocodile-like appearance. These structures serve as defence against predators and contribute to camouflage in leaflitter environments. The reinforced scalation may also help reduce water loss in their humid rainforest habitat.  

2. Feigning Death Through Thanatosis  

When threatened, red-eyed crocodile skinks can employ  thanatosis, a rare and dramatic defence mechanism. In this state, they become almost immobile, simulating death. For predators, a dead or dying meal can be an unappetising one. Thanatosis can also help the skink remain unnoticed until it is safe to scurry away. This complex behavioural display is uncommon in lizards and more frequently observed in snakes or small mammals.

 3. Eye Colour as a Maturity Marker  

The vibrant  reddish-orange ring encircling the eyes emerges only upon reaching adulthood. Juvenile red-eyed crocodile skinks display a more subdued olive or brown colouration and lack the prominent eye-ring entirely. This muted coloration likely functions as an adaptive camouflage mechanism, helping juveniles blend into their leafy and bark-laden forest floor habitat. The appearance of this red eye-ring coincides with full physical maturity and readiness to defend territory or offspring.   

4. Unique Single-Egg Reproduction  

Although female red-eyed crocodile skinks possess two ovaries, only the  right oviduct is functional, meaning they lay  a single egg per clutch. Remarkably, females may produce multiple clutches over a season. It takes roughly six weeks for one egg to hatch and another to be laid. This unusual reproductive strategy is thought to support intensive maternal investment in each offspring – an evolutionary trade-off for quality over quantity.  

5. Giants in a little genus 

Red-eyed crocodile skinks can grow to around 20 cm in length. This may seem rather small compared to other lizards but within the Tribolonotus genus, they’re rather large! They are actually 2.5 times larger than T. schmidti and T. blanchardi. Only T. ponceleti, is larger within the genus.  

6. Crocodile Skinks are Bio-Fluorescent  

Under UV lights, red-eyed crocodile skinks shine green. The biofluorescence is localised to the head, eyes, throat, ventrical region and lateral and dorsal scale tips. This biofluorescence may be used in communication or avoiding predation. There has also been a subtle sexual dimorphism detected between the biofluorescence of males and females within tribolonotus, which could help the skinks know what sex their counterpart is! 

7. Aquatic Adaptations & Breath-Holding Endurance  

Red-eyed crocodile skinks frequent moist, riparian rainforest zones and are comfortable entering water. Although direct physiological data is scant, anecdotal observations from keepers suggest they can  slow heart rate and metabolic demands while submerged, aiding extended breath-holding. Anatomical features – such as  water-resistant skin, tightly closing glottal valves, and lung adaptations – support aquatic survival and prevent water ingress during immersion. 

8. Kids Live Rent Free 

Red-eyed crocodile skinks have been found to live in small groups in the wild. These usually consists of one male with one or two females and their offspring. The offspring may stay in the family unit until maturity. This has also been demonstrated in captivity, although cohabiting a male with only one adult female is advised. 

9. Males vs Females 

Male and female red-eyed crocodile skinks may look indistinguishable from a distance but there are a few tell-tale signs to determine the sex once they are matured. The first is that males are usually larger and bulkier with wider heads. The second is the hind feet. Males exhibit slightly raised greyish-blue femoral pores on the underside of the third, fourth, and occasionally fifth digit. 

10. Vocal Signals & Active Parental Defence  

Red-eyed crocodile skinks are among the few skinks that  produce vocal distress calls. These high-pitched squeaks are more reminiscent of small mammals than reptiles. A 2001 study confirmed that such calls are produced by adults, including mothers defending their eggs and offspring.   

If you enjoyed these facts, you can learn more about red-eyed crocodile skinks and how to keep them as pets here.