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)
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.
There are no known negative impacts of this species on humans.
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.
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).
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 )
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
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).
Average lifespan
Status: captivity: 14.5 years.
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).
Range mass: 600 to 900 g.
Other Physical Features: heterothermic
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).
Tiliqua rugosa, most commonly known as the shingleback skink or bobtail lizard, is a short-tailed, slow-moving species of blue-tongued skink (genus Tiliqua) endemic to Australia. It is commonly known as the shingleback or sleepy lizard. Three of its four recognised subspecies are found in Western Australia, where the bobtail name is most frequently used.[3] The fourth subspecies, T. rugosa asper, is the only one native to eastern Australia, where it goes by the common name of the eastern shingleback.
Apart from bobtail and shingleback, a variety of other common names are used in different states, including two-headed skink,[4] stumpy-tailed skink, bogeye or boggi,[5] pinecone lizard.[6] The Noongar Aboriginal people refer to rugosa as yoorn in their language.[7]
T. rugosa has a short, wide, stumpy tail that resembles its head and may serve the purpose of confusing predators. The tail also contains fat reserves, which are drawn upon during brumation in winter, during which many lizards perform a behaviour similar to hibernation except they require water every day, but can go without food. This skink is an omnivore; it eats snails and plants and spends much of its time browsing through vegetation for food. In human habitation, it is often seen basking on roadsides or other paved areas.
The species was first described by John Edward Gray in 1825 as Trachydosaurus rugosus.[2][6] It is now classified as Tiliqua rugosa. Some herpetologists claim this species has more common names than any other lizard.[4]
Four subspecies of Tiliqua rugosa are currently recognised:[6]
The species is widely distributed in arid to semiarid regions of southern and western Australia. The range extends from Shark Bay, Western Australia, across the southernmost regions of the country to the coast, then north into Queensland. Four subspecies are found in Western Australia, including one at Rottnest Island. It also lives in the eastern states of Victoria and New South Wales, but does not reach coastal areas in these states.[11]
The habitat of the species includes shrub lands, eucalyptus forests, desert grasslands, and sandy dunes. They often shelter in the bush under low foliage. Being cold-blooded, these skinks are well known to have a strong preference for sun basking in open areas, and are often seen along roadsides or other cleared areas in its range.[12] On average, individuals have a home range of four hectares, and can move up to 500 metres per day.[13]
These lizards show strong home range site stability for up to several years and often multiple lizards can utilise the same burrow. As conditions become hotter and drier these lizards tend to share the burrows. During the spring time and given an adequate source of food that season and normal mating behaviour, males can often overlap each other's ranges. This can lead to territoriality and agonistic behaviour.[14]
Tiliqua rugosa has a heavily armoured body and can be found in various colours, ranging from dark brown to cream.[4] Its snout–vent length varies from 260 to 310 mm (10 to 12 in),[15] and it is very heavy-bodied for its length.[4] Their eyes are small with a reddish-brown and grey colour.[5]
It has a triangular head and a bright blue tongue,[4] inside a bright pink mouth.[5] Its short, stumpy tail is similar in shape to its head. This is probably a defence mechanism to confuse predators although it also stores fat and has led to the common name of "two-headed skink".[4] Unlike many skinks, shinglebacks do not exhibit autotomy and cannot shed their tails.[16]
The average lifespan for these skinks is 10 to 15 years, but some individuals have been known to live for as much as 50 years in the wild.[17]
The species normally shed their skin as a whole, including the eye covering. This takes up to several hours, during which the lizard rubs against objects to help the process.
The species exhibits sexual dimorphism, with males being stockier than females and having a larger head although females generally grow larger than males.
T. rugosa is an omnivore that eat snails, insects, carrion, vegetation and flowers. Since they are slow-moving, they tend to eat other slow moving species. This is perhaps why T. rugosa has a stronger preference for plants than other blue-tongue skink species. They can easily crush through the shells of snails with their strong jaws.[5]
As they overlap with human habitation and settlement, they have also been known to eat human food, such as sausage and chicken, as well as fruits such as strawberries, banana and passionfruit.
T. rugosa live a very sedentary lifestyle and generally act peacefully toward other individuals.[4] However, these lizards are territorial and can display agonistic behaviour towards conspecific intruders. They have stable home ranges and can differentiate between individuals through chemical cues. Familial neighbours who share home ranges and burrows do not show aggressive behaviour. However, unfamiliar males will be attacked by other males in occasional agonistic interactions. Scale damaged has allowed for the observation that unpaired males are more likely to display agonistic behaviour towards each other.
They are floating males and thus wander many home ranges with male inhabitants. T. rugosa performs almost no parental care, so the observed monogamy is only advantageous premating.[14]
The shingleback skink has become a popular pet among Australian enthusiasts. They are relatively docile and easy to feed and maintain. A permit may be required to keep them in some states. Skinks will bite humans if threatened. These bites, although not venomous, will hurt like other animal bites and may cause the affected area to swell or bruise.[5]
The species was once preyed upon by dingos, Australian pythons such as Morelia spilota, and local peoples; today the potential threats are more likely to come from large, introduced feral species such as foxes and cats.[18] In the bush habitat in Western Australia, birds of prey like falcons and kookaburras, and large snakes will commonly prey on these skinks.[5]
Ticks and nematodes commonly parasitise this species by attaching under scales or in the ear.[5] The kangaroo soft tick, Ornithodoros gurneyi, has been studied as a common parasite of T. rugosa, with claims that it infects the skinks when they spend time under trees or shrubs, where they commonly shelter during hot summer days.[19]
They have many performative defence mechanisms for predators. T. rugosa tends to gape open its mouth and display its blue tongue, which is often accompanied with intense hissing. Since they have a harsh bite, it is used for defence if interactions worsen.
T. rugosa is a viviparous skink meaning that its young are born live rather than being hatched from eggs as with most other lizards. Pregnancy and parturition are incredibly taxing on females. Relative clutch mass is 26.8% ±1.5% that of the mother.[20]
Brood size may be from one to four — more usually two to three — relatively large offspring.[21] The trade-off with small litter size versus large body size increases their survival chances.[4] Females possess a well-developed placenta with which they feed their unborn young.[22]
Unlike most other lizards the species tends to be monogamous and tend to re-unite in pairs during September to November prior to the breeding season. Pairs have been known to return to each other every year for up to 20 years.[4][23] The breeding season is from December to April and the gestation period is usually 3–5 months.[22]
When they are born, the young immediately consume their afterbirth.[4] They stay with their parents for several months before becoming independent, but they remain in close proximity, forming a colony of closely related skinks.[4]
The male of a monogamous pair eats less while parenting, remaining alert and ready to give an alarm.[4] They will tail behind the female to protect them from rival males while the female fends for food.[24]
Forming monogamous pair bonds is a central facet of the bobtail lizard's life. Their excellent sense of direction allows the male to follow or pursue the female repeatedly, even outside of mating season. When one of the pair is killed, these skinks have even been observed grieving or brooding for their pair partner.[13]
Social monogamy is beneficial to female bobtail lizards more than males. This is why polyandry is seldom found but polygyny is more common. Females tend to prefer attentive males, and therefore hold the mating choice. Researchers have found that males have to prove themselves to the female by following them around for a couple of weeks before mating, to be selected as a mate. For this reason, females often prefer to stay with the same male in future years; they gain the value of consistency and confidence that the male will once again be attentive. Females that switch mate pairs some years have been found doing so when the male was less attentive in the previous year.[25]
There are many reasons for why monogamy is especially popular in bobtail lizards. First, having two long-term pairs enhances parental care as there are two parents to watch after, fend for, and acquire resources for the offspring. Additionally, monogamy makes it easier for males to guard female home ranges. In polygamous setups, guarding multiple female ranges against other males proves to be difficult and waste time and resources.
Extra-pair fertilisation, although more rare, tends to produce larger broods. However, the trade-off is that the female receives less attention in these setups, hence monogamy is most popular.[25]
Their hearing can be measured at the round window as cochlear microphonics and summating potential (of the cochlea), and compound action potential and single-fibre responses (of the auditory nerve). These indicate a best hearing range near 1000 Hz. Earlier reports that their hearing sensitivity varied with the season[26][27] have been shown to be an artefact of the seasonally varying sensitivity to anesthetics.[28]
Single-unit recordings from the auditory nerve show both spontaneous and nonspontaneous responses. Tuning curves show peak sensitivity between 200 Hz and 4.5 kHz. The absolute sensitivity is quite high, with some thresholds at 6 db sound pressure level, very close to human best sensitivity.[29]
The sense of smell is crucial for this species avoidance behaviours. Living in bush lands that are so prone to fire means skinks have to easily be able to detect smoke. During studies, it was proven that T. rugosa engaged in more active behaviour such as pacing and tongue flicking in the presence of smoke. Scientists have concluded that fires are detected by their olfactory senses.[30]
It has been discovered that bobtail lizards maintain the ability to navigate home when displaced from their home range. This remarkable ability is due to visual cues from light polarisation and ferromagnetic detection, forming a sort of "celestial compass" that provides the lizard a sense of direction when coming back home. However, this ability only persists until about 800 metres out of the home range, and further displacement distances means the skink is too far away to navigate.
Under the IUCN Red List, Tiliqua rugosa is categorised as Least Concern. They are a protected species in Australia and can only be exported lawfully under a federal permit, but their import into and trade between other countries is not commonly illegal.[31] Its population is stable and for the most part there are no significant threats.[32] However, the subspecies T. r. konowi, located on Rottnest island, is considered Vulnerable.[33]
Western shingleback 
Rottnest Island shinglebackTiliqua rugosa, most commonly known as the shingleback skink or bobtail lizard, is a short-tailed, slow-moving species of blue-tongued skink (genus Tiliqua) endemic to Australia. It is commonly known as the shingleback or sleepy lizard. Three of its four recognised subspecies are found in Western Australia, where the bobtail name is most frequently used. The fourth subspecies, T. rugosa asper, is the only one native to eastern Australia, where it goes by the common name of the eastern shingleback.
Apart from bobtail and shingleback, a variety of other common names are used in different states, including two-headed skink, stumpy-tailed skink, bogeye or boggi, pinecone lizard. The Noongar Aboriginal people refer to rugosa as yoorn in their language.
T. rugosa has a short, wide, stumpy tail that resembles its head and may serve the purpose of confusing predators. The tail also contains fat reserves, which are drawn upon during brumation in winter, during which many lizards perform a behaviour similar to hibernation except they require water every day, but can go without food. This skink is an omnivore; it eats snails and plants and spends much of its time browsing through vegetation for food. In human habitation, it is often seen basking on roadsides or other paved areas.
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