Animal Diversity Web

Geographic Range

Tiliqua rugosa is currently one of the more abundant reptles that inhabits Australia. They range throughout the drier parts of Southern Australia, from approximately Bathurst in New South Wales all the way to the coast of Western Australia. T. rugosa is, for the most part, exclusive to the above areas and is never found naturally in the highly populated southeastern coast or any portion of Northern Australia (Walls, 1996).

• Biogeographic Regions
• australian
  • native

Habitat

Tiliqua rugosa inhabit semiarid plains and woodlands that typically have a harsh, dry summer and fall, followed by a cool winter and spring with increased precipitation and resources. These areas are subject to a great deal of variability in precipitation (Bustard, 1970).

• Terrestrial Biomes
• chaparral

Physical Description

Shingle back skinks are among the largest of the Australian skinks. Mature adults typically weigh 600 to 900 grams and have snout-vent lengths (SVLs) of 16 to 18 inches (VItt and Pianka, 1994). Tiliqua rugosa has an extremely short, blunt tail, being only one quarter of the SVL. The tail very much resembles the head of this species, and could probably be very easily as such by a would be predator. The scales of the body and tail are typically very large in size, and have a rough, knobby appearance, making this creature greatly resemble a pine cone. Head scales are fragmented and irregular, making them difficult to count and compare to other reptiles. The tongue of T. rugosa is cobalt blue in color, and is used extensively as a sensory organ, in conjunction with the Jacobson's organ. The dentation of this species is acrodont, meaning that the teeth are set on the edges of the jaw bones and are not in grooved sockets (Bustard, 1970). The legs in the shingle back skink are noticeably reduced, with the hind limbs being approximately twenty percent of the SVL, and the toes are short and fat (Cogger, 1975). Ear-openings are conspicuous and without anterior lobules (unlike genus Tiliqua). It is thought that males have a more slender, slightly longer tail than females, although this is by no means a sure way to sex this species. A better way of sexing is by cloacal examination (male hemipenes can be everted with pressure).

Coloration can vary greatly in the shingle backs, with three subspecies being recognized by these differences: T. r. rugosus of western Australia is classified as having a moderately long, slender tail and is brownish-red in color with yellow spots or white bands; T. r. konowi of Rattnest Island is small and dark, with gray coloration and numerous tiny, white specks on the belly and back; and T. r. asper of eastern Australia has the shortest, widest tail, with a very fragmented scalation pattrn and is usually solid brown with no pattern at all (Walls, 1996).

• Other Physical Features
• heterothermic

• Range mass

  600 to 900 g

  21.15 to 31.72 oz

Reproduction

Tiliqua rugosa are viviparous, typically producing 1 to 2 young, although triplets do occasionaly occur. A type of placenta very much like that of primitive mammals is formed between the mother and young. This permits the exchange of food and waste between the mother and the developing embryos (Cogger, 1967). Young are produced in late March or early April of each year after approximately 5 months of gestation. Young lizards weigh about 60 to 140 grams at birth and have a relative clutch mass (as a percentage of female gravid mass) of about 28%. The small litter size of young but the large size of individuals is believed to reduce risk of predation and aid in the potential survival through the oncoming winter months (Vitt and Pianka, 1994). Copulation is usually observed around late October or early November and is typically over with very quickly. There is a great deal of evidence that shingle backs are monogamous (see behavior section).

Lifespan/Longevity

The shingle back skink has an average life span of about 10 to 15 years, although there is a living and healthy specimen which resides as a captive in England (his name is Stumpy), that is an amazing 35 years old! However, that is extremely rare and would be even more rare in the wild (Walls, 1996). (Walls, 1996)

• Average lifespan
  Status: captivity

  14.5 years

  Max Planck Institute for Demographic Research

Behavior

Tiliqua rugosa are colonial in nature, and are therefore not aggressive towards one another. They are usually sedentary but do move about sometimes, although usually returning to the same home range. Home ranges of individuals (undefended areas of inhabitance) are about 200 meters in diameter but do not usually have any particular shape; they tend to overlap one another (Vitt and Pianka. 1994).

The skin of T. rugosa tends to be molted about 4 or 5 times a year.

The Tiliqua rugosa daily routine typically starts with a warming period in the morning, followed by active feeding and continued basking, then finding shelter under litter, logs, or debris as the temperature falls towards the end of day.

The defensive behavior of this organism is exhibited when threatened. Once threatened, the animal usually tries to bluff its way out. It gapes its huge mouth wide open and protrudes its large blue tongue, while hissing violently at the same time. It usually orients itself to face its enemy, and if within reach, shingle backs will attempt to bite. Bites can be quite painful due to their strong jaws and fairly sharp teeth.

An 11 year study was conducted on these reptiles from 1981 to 1992. It showed that males typically stayed with one female and vice versa over extended periods of time. After copulation, pairs usually separate for 10 months and then pair again with the same partner the following year. Although the chance of pairs remaining together decreases with an increasing amount of years (this is partly due to death of partners), one pair has been found together for 10 consecutive years (Vitt and Pianka, 1994). This study illustrate long-term individual recognition by this species and also shows that these reptiles are monogamous more often than not. This is extremely rare in reptiles!

Food Habits

The shingle back is an omnivore that would be considered an opportunistic feeder. Its main diet typically consists of vegetable matter, such as herbs and seedlings, with any blossoms or fruits that it may come across included. The rest of the diet can consist of insects and other arthropods, snails, carrion, and basically any other edible thing that it is fortunate enogh to come across (Cogger, 1975). One of the greatest hardships that T. rugosa is adept at overcoming are periodic droughts and famines Typically, much food is available during the spring months after the winter rains, but that soon plummets during the following summer and fall months. As was discussed above, the tail acts as a fat store to help the shingle back survive in times if little or no sustenance. Its opportunistic feeding habits also aid in its survival (although the tendency to venture out into the road to consume carrion and then be struck and killed by motor vehicles is a leading cause of death in this species) (Vitt and Pianka, 1994).

Economic Importance for Humans: Positive

Aboriginals have found T. rugosa to be a good source of food and some southern tribes of Australia used them medicinally. They are believed to kill and eat snakes, which has been witnessed but is not typical behavior(Serventry, 1977). The shingle back skink also plays a small part in the world pet trade. Exportation of this species from Australia is currently prohibited but there are some pairs in the trade that have been producing captive young for private collections. These captives command a high price and are fairly rare to come across.

Economic Importance for Humans: Negative

There are no known negative impacts of this species on humans.

Conservation Status

Tiliqua rugosa are quite common in Australia and do not suffer from many natural predators. Road side killings tend to be the most devastating force on wild populations. A study of percent population loss of this species due to road kill was conducted and the results showed an average annual 11.9% population loss. These results greatly contrasted with an estimate by Ehmann and Cogger (1985) that 0.014% of all mortality in Australian herpetofauna is dure to road kills. This suggests that T. rugosa is very susceptible to this form of mortality, probably due to their feeding habits outlined above.

• IUCN Red List

  No special status

Other Comments

The shingle back skink has been the subject of some debate concerning nomenclature. Some taxonomists believe it to belong to Tiliqua, while others believe it should be in its own genus (Trachydosaurus). I have used the Trachydosaurus nomenclature here because of numerous differences between T. rugosa and Tiliqua genus can be seen. Studies of the animal's molecular chemical composition suggest it to be identical to the Tiliqua genus, but T. rugosa has many scalation and body differences that are very distinguishing. It also has divided lamellae on the toes of the hind feet and the absence of the ear lobules that are characteristic of the Tiliqua genus (Walls, 1996)

Contributors

Thomas Loch (author), Michigan State University, James Harding (editor), Michigan State University.

References

Bustard, R. 1970. Australian Liards. Australia: William Collins Ltd..

Cogger, H. 1964. Austalian Reptiles in Colour. Honolulu: East-West Center Press.

Cogger, H. 1975. Reptiles and Amphibians of Australia. FL: Ralph Curtis Books.

Serventry, V. 1977. Wildlife of Australia. London: Hamish Hamilton Ltd.

Vitt, L., R. Pianka. 1994. Lizard Ecology. NJ: Princeton University Press.

Walls, J. 1996. Blue-Tongued Skinks. NJ: T.F.H. Publications,Inc..