The Blotched Blue-tongue Lizard (scientific name Tiliqua nigrolutea) is a large, heavy-bodied skink native to south-eastern Australia and Tasmania. Also known as the southern blue-tongued lizard or blotched blue-tongued skink, it is famous for its chunky build, short sturdy legs and the vivid blue tongue it flashes when threatened. In many farms and country gardens it is regarded as a welcome guest because it helps control snails, slugs and other garden pests.
Taxonomy and naming
The Blotched Blue-tongue Lizard belongs to Class Reptilia, Order Squamata, Family Scincidae (skinks), and Genus Tiliqua. This genus contains several well-known blue-tongued skinks that are iconic Australian reptiles. The word “blotched” in its common name refers to the pale blotches and patches on its back, which distinguish it from other blue-tongue species such as the Eastern Blue-tongued Lizard.
Physical characteristics
This species has a large, robust body with a broad head, short but powerful limbs and a relatively short tail, giving it a chunky appearance. Colour and pattern vary geographically and two main forms are often recognised: a lowland form and a highland form. Lowland animals tend to be grey or brown with paler silver to tan blotches along the back set against darker bands, while highland animals are much darker, often jet black, with striking cream, pink or orange blotches. The most distinctive feature is, of course, its fleshy blue tongue, which it displays dramatically inside a pink mouth when it feels threatened.
Distribution and habitat
The Blotched Blue-tongue Lizard is endemic to south-eastern Australia. It occurs in Victoria, Tasmania, parts of South Australia, New South Wales and the Australian Capital Territory. It occupies a wide range of habitats, including wet and dry sclerophyll forests, montane woodlands, subalpine shrublands and coastal heathlands. The species also adapts well to modified landscapes, and is often found in farms, pastures and rural or suburban gardens where it shelters in rock piles, wood stacks, dense shrubs and deep leaf litter.
Behaviour and lifestyle
Blotched blue-tongues are mainly diurnal and most active during mild parts of the day, especially in the morning and late afternoon. During the cold winter months they enter a period of dormancy or brumation, emerging in early spring when temperatures rise and the breeding season begins. When threatened, they usually rely on camouflage and slow retreat at first. If danger persists, they inflate their body, hiss loudly, open the mouth wide and flash the blue tongue in an impressive bluff display. Only as a last resort will they bite, and although the jaws are strong and the bite can be painful, the teeth are blunt and rarely break the skin.
Diet
The Blotched Blue-tongue Lizard is an omnivore with a very broad diet. It feeds on beetles and other insects, spiders, snails, slugs and many other invertebrates, as well as flowers, soft leaves, wild fruits and fallen berries. When the opportunity arises, it may also consume carrion and small vertebrates such as nestling rodents. This flexible diet allows it to thrive in a variety of habitats and makes it particularly useful in gardens and agricultural areas as a natural pest controller.
Reproduction and life cycle
Like other blue-tongued skinks, the Blotched Blue-tongue Lizard is viviparous: females retain the developing embryos in the uterus and give birth to fully formed live young instead of laying eggs. Mating typically occurs in early spring after the animals emerge from brumation, and gestation is relatively long. Young are usually born in autumn. Reproductive output differs between forms: highland females tend to produce fewer but larger young (around five per litter), whereas lowland females may give birth to about ten or more offspring. Individuals grow slowly and take several years to reach sexual maturity. Wild lizards commonly live for around 15–20 years, while well-cared-for captives may live 20–30 years or more.
Relationship with people
In many rural and semi-urban areas of south-eastern Australia, Blotched Blue-tongue Lizards are familiar backyard wildlife. By eating snails, slugs and other invertebrate pests, they help reduce damage to crops and garden plants and can lessen the need for chemical pesticides. Unfortunately, they are sometimes injured on roads or attacked by dogs and cats, and are occasionally harmed by people who mistake them for dangerous reptiles. In reality, they are gentle, slow-moving lizards that prefer to avoid conflict, and simply watching them from a respectful distance is the best way to appreciate them.
Conservation status and threats
According to the IUCN Red List, the Blotched Blue-tongue Lizard is currently listed as Least Concern, with an overall stable population across its wide range. However, local populations can still be affected by habitat loss and fragmentation due to agriculture and urban development, road mortality, poisoning from pesticides and rodenticides, and predation by introduced mammals such as foxes and domestic cats and dogs. Protected areas such as national parks provide important refuges, and public education campaigns that encourage people not to harm blue-tongues and to reduce the use of toxic chemicals in gardens are also beneficial for their long-term conservation.
References
Cogger, H.G. 1994. Reptiles & Amphibians of Australia. Reed Books, Sydney.
Ehmann, H. 1992. Encyclopedia of Australian Animals. Reptiles. Australian Museum and Angus & Robertson, Sydney.
Greer, A.E. 1989. The Biology and Evolution of Australian Lizards. Surrey Beatty & Sons, Sydney.
Weigel, J. 1988. Care of Australian Reptiles in Captivity. Reptile Keepers' Association, Gosford.
Wilson, S.K. & Knowles, D.G. 1988. Australia's Reptiles: A Photographic Reference to the Terrestrial Reptiles of Australia. William Collins, Sydney.
