Tiliqua gigas, commonly known as the giant blue-tongued skink, is best known for its bright blue tongue. It is a gray lizard about 31cm from the snout to the base of the tail and 55cm from the snout to the tip of the tail, with dark flanks and legs and lateral stripes. Its threat display, in which it opens its mouth wide to display its tongue and makes a loud hissing noise, is so striking that the Malay-speaking people of New Guinea called it “ular kaki ampat” or “snake with four legs” and feared for a long time that it was extremely venomous. In actuality, however, the lizard is fairly harmless - the most substantial documented medical danger of blue-tongued skink bites is secondary infection from bacteria living in the mouth. Tiliqua gigas is an omnivore and is often associated with human agricultural settlements. A broad diet and distinctive appearance have recently made this species and its relatives popular as pets (de Rooij 1915, Brongersma 1958, Broaddus 1994, Gorseman 1998, Dennert 2004).
Distribution: Indonesia (Ambon, Ceram, Ternate, Halmahera, Ke, Aru), Papua New Guinea, Jobi, Admirality Islands, New Britain, Bismarck Archipelago. evanescens: E/S Papua New Guinea, Indonesia (Irian Jaya).
Tiliqua gigas lives in Indonesia (Ambon, Ceram, Ternate, Halmahera, Mysol, Ke, Aru), Papua New Guinea, Jobi, the Admiralty Islands, New Britain, and the Bismarck Archipelago (Barbour 1912, JCVI/TIGR 2010).
According to Gorseman (1998), T. gigas is found in the easternmost part of Java, in Sumatra, on many of the Moluccas, the Kai Islands, the Tanimbar Islands, and Halmahera, on the entire southern and western coasts of Irian Jaya and Papua New Guinea, as well as the northeastern edge of Papua New Guinea.
The eyelids are distinct and scaly. The ear opening is about as large as the eye opening and two or three large, obtuse lobules are present anteriorly. The nostril is within the nasal scale and there are no supranasals. The frontonasal is in contact with the rostral and the prefrontals form a suture. The frontal is longer than it is broad, as long as the parietals, and is in contact with the two anterior supraoculars. There are four supraoculars, of which the second is largest. There are between six and seven supraciliaries. The frontoparietals are distinct. The interparietal is as broad as the parietals are narrow. There are usually three anterior temporals which are larger than the others, and the parietals are separated. The body is stout, with 28-32 subequal scales around the middle. Dorsal scales are usually keeled. The tail is about as long as the body and is compressed, and the dorsal caudal scales are keeled. The limbs are short, with the forelimb a little longer than the head; its length is contained nearly 2.5 times in the distance between the axilla and the groin. The digits are short and round, and possess undivided lamellae ventrally (de Rooij 1915).
The body is light brown dorsally, with eight to ten dark brown cross-bands. The flanks and limbs are dark brown, spotted with yellow. The head-shields are edged with brown. A dark brown median line is present on the nape, and the tail is banded. The ventral parts are brown and yellow. The head and body together are 312mm long, and the tail is 245mm long (de Rooij 1915).
It is often difficult to distinguish males from females before sexual maturity, but Gorseman (1998) notes that adult males are “much more heavily built than females", and that "they also have a darker head and develop a type of throat sac.”
Tiliqua gigas is thought to be most closely related to T. scincoides, the better-known Australian blue-tongued skink, but the two possess different color patterns. Tiliqua scincoides is light in color, or at least possesses both dark and light cross-stripes, whereas T. gigas has dark flanks, tending toward black, with at most vaguely present stripes (Gorseman 1998).
Tiliqua gigas is a terrestrial lizard with relatively limited climbing ability. In contrast to other species of Tiliqua, which prefer more arid habitats (Dennert 2004, Souter et al. 2007), T. gigas thrives in warm, moist coastal lowlands especially near agricultural or disturbed landscapes (Gorseman 1998).
The biogeograpy of Tiliqua gigas has yet to be thoroughly elucidated, but based on the biology of this species and known biogeographical trends in other Australasian species, Gorseman (1998) speculated that its ancestors probably dispersed from Asia to New Guinea and the neighboring islands by floating on branches and/or hitchhiking on merchant vessels.
Tiliqua gigas appears to be an omnivorous scavenger (Gorseman 1998, Dennert 2004). Its large size among skinks may be correlated with a higher degree of herbivory than is typical of smaller skinks (Greer 2001). It is especially active in agricultural regions, where it is commonly found in piles of garbage, especially those containing coconut husks. It also likes snails and may eat arthropods, smaller lizards, and occasionally carrion (Gorseman 1998).
Tiliqua gigas appears to be a terrestrial, omnivorous scavenger (Gorseman 1998, Dennert 2004). Its large size among skinks may be correlated with a higher degree of herbivory than in smaller skinks (Greer 2001). It is especially active in agricultural regions, where it is commonly found in piles of garbage, leading Gorseman (1998) to suggest that it follows human settlements to colonize new areas.
Life History and Behavior
The gait of Tiliqua gigas has been described as “shuffling” and “slow” (Gorseman 1998). Although T. gigas is typically terrestrial, individuals have been observed climbing up to 80cm off of the ground in a terrarium, apparently by standing against a tree trunk and pulling themselves up with their legs. They are capable of tail autotomy (i.e., loss of the tail) and regeneration. Some keepers of T. gigas have reported instances of aggression between captive individuals (Gorseman 1998).
While relatively little is known about the behavior of Tiliqua gigas in particular, blue-tongued skinks in general tend to be medium- to large-sized omnivorous lizards. Many spend substantial amounts of time resting in burrows, although they are likely to forage relatively actively during the day, especially during the wet season when food resources are more abundant (Christian et al. 2003). The most striking aspect of blue-tongued skink behavior, though, is the threat display: when threatened, blue-tongued skinks hiss loudly while opening their mouths to display their bright blue tongues (Brongersma 1958, Broaddus 1994).
Behavioral seasonality has not yet been studied in detail in Tiliqua gigas, but other blue-tongued skinks have been shown to be significantly more active (both in locomotion and metabolism) during the wet season compared to the dry season when food resources are scarce (Christian et al. 2003).
Lifespan, longevity, and ageing
Little is know about the reproduction of Tiliqua gigas in the wild. They are ovoviviparous, and have been observed in captivity to have a gestation period of approximately 200 days, giving birth to litters of 4-6 young with snout-vent lengths of approximately 8cm and total body lengths of approximately 13.5cm. Some keepers have noted that males often injure females during copulation (Gorseman 1998).
Evolution and Systematics
The genus Tiliqua, along with the other Australasian skink genera Corucia and Egernia, have long been understood to form a clade called the Mabuya group, but relations within that group have been more difficult to elucidate. Among these three genera, Greer (1970) found Corucia and Egernia to be most closely related in a phylogenetic analysis of morphological data, but in a phylogenetic analysis using immunodistances, Hutchinson (1981) found instead that Tiliqua and Egernia formed a clade sister to Corucia. A more recent study using portions of the mitochondrial 12S and 16S rRNA genes found Corucia and Tiliqua to be the most closely related genera of the three (Honda et al. 1999).
Molecular Biology and Genetics
Honda et al. (1999) sequenced portions of the mitochondrial 12S and 16S rRNA genes and found the genus Tiliqua to be most closely related to another Australian skink genus, Corucia. Several nucleotide sequences from Tiliqua gigas are available in the NCBI nucleotide database, inclucing MYH, Gadph, Cytb, and partial sequences from the 12S and 16S rRNA genes.
Statistics of barcoding coverage: Tiliqua gigas keyensis
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
Relevance to Humans and Ecosystems
Tiliqua gigas is used in the pet trade (Gorseman 1998), and much has been written about its care and breeding in captivity (Hauschild et al. 1999, Dennert 2004). In short, T. gigas can be kept in terraria at 25-30°C on a basic diet of bananas and canned cat food, although it appears to like snails too. Gorseman (1998) recommends keeping these skinks in a high humidity environment and providing them with several hiding places, presumably to reduce stress.
|This article needs additional citations for verification. (January 2013)|
|This skink article is a stub. You can help Wikipedia by expanding it.|