Adelaide pygmy bluetongue skink (Tiliqua adelaidensis)

Description

Adelaide pygmy bluetongue skink fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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Adelaide pygmy bluetongue skink description

The Adelaide pygmy bluetongue skink is one of the rarest of Australia’s reptiles ⁽³⁾. It has a large head, heavy body, short limbs and toes, and a tapering tail ⁽²⁾. The upperparts may be light grey-brown, yellowish-brown, orange-tan or chocolate brown, while the limbs are often a pale yellowish colour and the underparts are pale grey to whitish ⁽²⁾. Most individuals are patterned with a scattering of dark spots and blotches ⁽⁴⁾. With this body colouration, the skink is splendidly camouflaged against the reddish-brown soil of its habitat. Surprisingly, the tongue of this skink is not blue as the name suggests, but is instead a rose pink colour, and the roof of the mouth is mauve ⁽²⁾.

The adult male Adelaide pygmy bluetongue skink is shorter than the female but has a relatively larger head. It is thought that the larger head size may have evolved in response to male combat ⁽²⁾. Juvenile Adelaide pygmy bluetongue skinks are greenish-grey to mid-brown, becoming reddish-tan on the tail and limbs ⁽²⁾.

Also known as

Adelaide pigmy blue-tongue skink, pygmy bluetongue.

Size

Male snout-vent length: 3.8 - 10.6 cm ⁽²⁾

Female snout-vent length: 8.8 - 10.7 cm ⁽²⁾

Tail length: 2.2 - 7.9 cm ⁽²⁾

Adelaide pygmy bluetongue skink biology

The Adelaide pygmy bluetongue skink shelters in holes that, rather than being excavated by the skink itself, are quarried by wolf spiders and trapdoor spiders (lycosid and mygalomorph spiders). The almost vertical burrow, measuring about 24 centimetres deep ⁽²⁾, serves as a shelter during the day when the temperature is too hot, as a retreat if threatened while basking, as a place from which to ambush passing prey, and as a birthing site ⁽⁷⁾.

The Adelaide pygmy bluetongue skink gives birth to live young. Females give birth to litters of one to four young in maternal burrows in February or March ⁽²⁾. After the juveniles reach two weeks of age, they leave the burrow and inhabit smaller, separate burrows. Breeding age is reached at about 20 months ⁽²⁾.

The diet of this skink consists mainly of a wide range of invertebrates, such as spiders, grasshoppers, cockroaches and ants, but it will also feed on plants ⁽²⁾. It is largely a “sit-and-wait” predator, lying at the entrance of its burrow and waiting to launch a surprise attack on any prey item that comes too close, but it may also forage further away from the burrow ⁽²⁾.

Although active during the day, the Adelaide pygmy bluetongue skink is a shy, cryptic reptile. As well as its body colouration providing good camouflage in its habitat, it often lies partially emerged from the entrance of its burrow, enabling it to retreat rapidly back into safety at the first sign of danger. Once inside its burrow, the lizard wedges its relatively large head, heavily armoured with large, thick scales, against the entrance ⁽²⁾. By blocking the entrance, and presenting only a heavily armoured head, few predators small enough to have access to the hole would be strong enough to prise the skink out, providing the Adelaide pygmy bluetongue skink with an excellent defence strategy. On the rare occasions when a skink forages away from the burrow, it will freeze if alerted to the presence of a potential enemy ⁽²⁾.

Adelaide pygmy bluetongue skink range

The Adelaide pygmy bluetongue skink is restricted to an area located 160 kilometres north of Adelaide, South Australia ⁽⁵⁾.

Adelaide pygmy bluetongue skink habitat

Today, all known populations of the Adelaide pygmy bluetongue skink inhabit degraded native grassland or grassy woodland ⁽⁶⁾.

Adelaide pygmy bluetongue skink status

Classified as Endangered (EN) on the IUCN Red List ⁽¹⁾.

Adelaide pygmy bluetongue skink threats

The Adelaide pygmy bluetongue skink was once feared to be the first of Australia’s approximately 700 reptiles to become extinct since European colonization. Thankfully, it was rediscovered in 1992 after 33 years of being presumed extinct ⁽³⁾. Currently, only ten small populations of the Adelaide pygmy bluetongue skinkare known to exist ⁽⁶⁾. Arguably Australia’s most enigmatic reptile, its scarcity can be attributed to its unique ecology as well as population declines due to extensive habitat destruction ⁽²⁾(3).

Conversion of native vegetation to pastureland has altered the skink’s original habitat so that previously inhabited areas no longer suit the species’ requirements ⁽²⁾. The native grasslands that this species requires were once extensive throughout South Australia, but being prime land for agriculture, most were cleared and ploughed in order to be converted to pasture and crops. This not only altered vegetation and ground cover, but ploughing would also have directly killed any skinks and destroyed the vital spider burrows, leaving any survivors without shelter and completely exposed to predators ⁽²⁾. 

Adelaide pygmy bluetongue skink conservation

The South Australia Department of Environment and Conservation has produced a National Recovery Plan for the Adelaide pygmy bluetongue skink, with the overall objective to achieve down-listing of the species from Endangered to Vulnerable within 10 years. The plan details actions such as ensuring remaining habitat is protected from any further degradation, and undertaking field studies to establish the skink’s habitat requirements ⁽⁶⁾. At present, all populations of the Adelaide pygmy bluetongue skink occur on private land, making the establishment of agreements with landowners an essential part of any plan, and incentives may be offered to landowners to become involved in establishing sanctuaries for the Adelaide pygmy bluetongue skink on their land ⁽⁶⁾.

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Glossary

Invertebrates

Animals with no backbone, such as insects, crustaceans, worms, and spiders.

References

1. IUCN Red List (March, 2010)
   http://www.iucnredlist.org/
2. Hutchinson, M.N., Milne, T. and Croft, T. (1994) Redescription and ecological notes on the pygmy bluetongue, Tiliqua adelaidensis (Squamata: Scincidae). Transactions of the Royal Society of South Australia, 118(4): 217-226.
3. Armstrong, G., Reid, J.R.W. and Hutchinson, M.N. (1993) Discovery of a population of the rare scincid lizard Tiliqua adelaidensis (Peters). Records of the South Australian Museum, 36: 153-155.
4. Department for Environment and Heritage (2005) Threatened Fauna Fact Sheet: Pygmy Bluetongue Lizard (Tiliqua adelaidensis). Department for Environment and Heritage, South Australia.
5. Cogger, H.G. (2000) Reptiles and Amphibians of Australia. Reed New Holland, Sydney.
6. Milne, T., Hutchinson, M. and Clarke, S. (2000) National Recovery Plan for the Pygmy Bluetongue Lizard (Tiliqua adelaidensis). Department of the Environment, Water, Heritage and the Arts, Canberra. Available at:
   http://www.environment.gov.au/biodiversity/threatened/publications/recovery/pygmy-bluetongue/index.html.
7. Milne, T. and Bull, C.M. (2000) Burrow choice by individuals of different sizes in the endangered pygmy blue tongue lizard Tiliqua adelaidensis. Biological Conservation, 95: 295-301.