Tiliqua rugosa

Bobtail Skink
Eastern Shingleback
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Family:	Scincidae
Genus:	Tiliqua
Species:	T. rugosa
Binomial name
Tiliqua rugosa (Gray, 1825)[1]
Subspecies
4, see text
Synonyms
Trachydosaurus rugosus

Western Shingleback

Rottnest Island Shingleback

Tiliqua rugosa is a short-tailed, slow moving species of blue-tongued skink found in Australia. Three of the four^[2] recognised subspecies are found only in Western Australia, where they are known collectively by the common name bobtail.^[3] The name shingleback is also used, especially for T. rugosa asper, the only subspecies native to eastern Australia.

T. rugosa has a heavily armoured body and can be found in various colours, ranging from dark brown to cream. It has a short, wide, stumpy tail that resembles its head and may confuse predators. The tail also contains fat reserves, which are drawn upon during brumation in winter. This skink is an omnivore; it eats snails and plants and spends much of its time browsing through vegetation for food. It is often seen sunning on roadsides or other paved areas.

Apart from bobtail and shingleback, a variety of other common names are used, including stump-tailed skink, bogeye, pinecone lizard and sleepy lizard.^[2]

Etymology and taxonomy

The species was first described by John Edward Gray in 1825 as Trachydosaurus rugosus.^[1][2] It now classified as Tiliqua rugosa. Some herpetologists claim this species has more common names than any other lizard.^[4]

Subspecies

Four subspecies of T. rugosa are currently recognized:^[2]

• T. r. rugosa: bobtail or western shingleback – Western Australia
• T. r. asper:^[5] eastern shingleback – eastern Australia
• T. r. konowi:^[6] Rottnest Island bobtail or Rottnest Island shingleback – Rottnest Island, Western Australia
• T. r. palarra:^[7] northern bobtail or Shark Bay shingleback – Shark Bay, Western Australia

Distribution and habitat

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 southern-most 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 occurs in the eastern states of Victoria and New South Wales, but does not reach coastal areas.^[8]

The habitat of the species includes shrublands and desert grasslands to sandy dunes. These skinks are well known, due to a preference for sun basking in open areas, and are often seen along roadsides or other cleared areas in its range.^[9]

Description

Threat display

T. rugosa has a heavily armoured body and can be found in various colours, ranging from dark brown to cream.^[4] Its snout to vent length varies from 260 to 310 mm (10 to 12 in),^[10] but it is a very heavy-bodied lizard for its length.^[4]

It has a triangular head and a bright blue tongue.^[4] Its short, stumpy tail is similar in shape to its head. This possibly evolved as a defence mechanism against predators, and has led to the common name of "two-headed skink".^[4] Its short tail also contains fat reserves, which the lizard lives upon during brumation in winter.^[4] Unlike many skinks, shinglebacks do not exhibit autotomy and cannot shed their tails.^[11]

Diet

front view

Tiliqua rugosa is an omnivore that eat snails, insects, carrion, vegetation and flowers. The species was once preyed upon by dingos, Australian pythons such as Morelia spilota, and local peoples; a threat is now more likely to come from large, introduced feral species, such as foxes and cats.^[12]

They have also been known to eat human food, such as sausage and chicken, as well as fruits such as banana and passionfruit.

In captivity

The shingleback skink has become a popular pet among Australian enthusiasts.

Reproduction

Captive specimens

T. rugosa is a viviparous skink, giving birth to broods of one to four relatively large offspring.^[4] Unlike most lizards, the species tends to be monogamous extending outside the breeding season of September through November; such pairs have been known to return to each other every year for up to 20 years.^[4][13]

Soon after birth, the young immediately consume their afterbirth.^[4] They stay with their parents for several months before moving on, 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]

Hearing

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,^[14][15] have been shown to be an artefact of the seasonally varying sensitivity to anesthetics.^[16]

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.^[17]

References

1. Gray, J.E. (1825). A synopsis of the genera of reptiles and Amphibia, with a description of some new species. Annals of Philosophy 10:193—217. p. 201
2. Tiliqua rugosa at the Reptarium.cz Reptile Database
3. City of Wanneroo (2009). "Bushland Critters" (PDF). Retrieved 2010-11-09.
4. Pianka, Eric R.; Vitt, Laurie J. (2003). Lizards: Windows to the Evolution of Diversity (Organisms and Environments, 5) 5 (1 ed.). California: University of California Press. ISBN 978-0-520-23401-7.
5. Gray, J. E. (1845). Catalogue of the specimens of lizards in the collection of the British Museum. London: Trustees of die British Museum/Edward Newman.
6. Mertens, R. (1958). "Neue Eidechsen aus Australien". Senckenbergiana Biologica (in German) 39: 51–56.
7. Shea, G. M. (2000). "Die Shark-Bay-Tannenzapfenechse Tiliqua rugosa palarra subsp. nov.". In Hauschild, A.; Hitz, R.; Henle, K.; Shea, G. M.; Werning, H. Blauzungenskinke. Beiträge zu Tiliqua und Cyclodomorphus (in German). Münster: Natur und Tier Verlag. pp. 108–112. ISBN 3-931587-33-9.
8. Cogger, Harold G. (2000). Reptiles and Amphibians of Australia. Sanibel Island, FL: Ralph Curtis Books. ISBN 0-88359-048-4.
9. Browne-Cooper, Robert; Brian Bush; Brad Maryan; David Robinson (2007). Reptiles and Frogs in the Bush: Southwestern Australia. University of Western Australia Press. p. 99. ISBN 978-1-920694-74-6.
10. Wilson, S. & Swan, G. (2003). A complete guide to reptiles of Australia. New Holland Publishers, Sydney. ISBN 1 876334 72 X
11. http://www.amnh.org/exhibitions/lizards/nose/shingle.php
12. C. M. Bull , and Y. Pamula (1998). "Enhanced vigilance in monogamous pairs of the lizard, Tiliqua rugosa" (PDF). Behavioural Ecology (Oxford University Press) 9 (5): 452–455. doi:10.1093/beheco/9.5.452. ISSN 1465-7279. Retrieved 2008-04-12.
13. Bull, C. Michael; Cooper, Steven J. B.; Baghurst, Ben C. (1998). "Social monogamy and extra-pair fertilization in an Australian lizard, Tiliqua rugosa". J. Behavioral Ecology and Sociobiology 44 (1): 63–72. doi:10.1007/s002650050515.
14. Johnstone, J. R. & Johnstone, B. M. (1969). "Electrophysiology of the lizard cochlea". Experimental Neurology 24 (1): 99–109. doi:10.1016/0014-4886(69)90008-9. PMID 4306107.
15. Johnstone, J. R. & Johnstone, B. M. (1969). "Unit responses from the lizard auditory nerve". Experimental Neurology 24 (4): 528–537. doi:10.1016/0014-4886(69)90156-3. PMID 5799201.
16. Koeppl, C.; Manley, G.A. & Johnstone, B.M. (1990). "Peripheral auditory processing in the bobtail lizard V Seasonal effects of anaesthesia". Journal of Comparative Physiology 167 (1): 139–144. doi:10.1007/bf00192413.
17. Manley, G.A.; Koeppl, C. & Johnstone, B.M. (1990). "Peripheral auditory processing in the bobtail lizard I Frequency tuning of auditory nerve fibers". Journal of Comparative Physiology 167 (1): 89–99. doi:10.1007/bf00192409.