Distribution: Australia (New South Wales, South Australia, Tasmania, Victoria)
The blotched blue-tongued lizard resides in southern parts of the Australian state of New South Wales and a smidgeon of the neighboring state of South Australia. There are several species of blue-tongued lizards in Australia. This one, Tiliqua nigrolutea is restricted to the highland areas between the Victorian border and the Blue Mountains. It also occurs on Tasmania and the islands of the Bass Strait (Jones and Edwards 1998, Shea 1997).
Biogeographic Regions: australian (Native )
The appearance of the blotched blue - tongued lizard is hinted in its scientific name: Tiliqua nigrolutea. Nigro and lutea mean black and yellow respectively. Indeed, this lizard is usually dark brown or black with yellow, cream or pink blotches on it. Although the blue-tongues are the largest members of the skink family (Scincidae), many of their characteristics differ from that of an average skink. First of all, they have an unusual body shape with a stout torso, short limbs and a thick, short tail. Furthermore, unlike smaller skinks, blue-tongues rarely lose their tails.
There are also differences between the males and females of the species. The males have proportionally bigger head and a more heavyset body. This is due to the shape of the two hemipenes (the male copulatory organs). Females are longer in length ((27-30cm to the males' 25-27cm). Because of this, the females are greater in mass weighing between 350 - 450g while males stay within the 300-350g range. (Cogger 2000, Jones and Edwards 1998).
Range mass: 300 to 450 g.
The blotched blue-tongue lizard resides in open country with lots of ground cover such as leaf litter and shrubs. At night, they find shelter under the leaf litter, rocks and logs. Because they cannot produce their own body heat, these skinks live in areas where they can bathe in sunlight during periods of the day in the summer. They need to maintain a body temperature of 30 - 35 degrees Celsius when active (Shea 1997).
Because of the great degree of human activity in New South Wales (e.g. the city of Sydney) and Tasmania, blue-tongues no longer live exclusively in the wild. Tiliqua nigrolutea have also adapted to suburban life. They can frequently be found in backyards where some will reside for many years. They will bathe in the sun on the lawns and paths while cooling off in the rockeries, pipes and cavities under the house (Jones & Edwards 1998).
Terrestrial Biomes: savanna or grassland
Blue tongues are omnivores and eat a great melange of plants and animals. Since these large skinks are not particularly agile, they eat mostly slow-moving animals such as snails and beetles. Their strong jaws are fashioned to crush the shells of their prey. They have a strong liking for strawberries. In captivity, they are given a diet of catfood and soft fruits such as bananas and kiwifruit. (Cogger 2000)
Life History and Behavior
Status: captivity: 11.5 years.
Lifespan, longevity, and ageing
These blotched blue-tongues like other blue-tongues are solitary animals except during mating season. Males and females emerge from hibernation at different times. The males come out in late September while the females come forth in late October. Mating occurs soon after in the months of November and December. Studies done at the University of Tasmania show that males begin to produce their sperm as early as the previous fall so that only the final stages of sperm production occurs in the spring. It is at this time that males fight aggressively among themselves. Furthermore the actual coital process can be very rough and violent in manner. Afterwards, females carry the scrape marks from the male's biting (Jones and Edwards 1998)
After impregnation, the embryos develop in their mother's oviduct with the help of an exceptionally well-developed placenta. The placenta contains a large yolky egg which supplies the nutrition for the developing young. The clutch size is generally around six. Earlier studies that put the clutch size at 25 have been dismissed because the strain would have been too much on the mother. At birth, the newborns eat the placental membrane. Within a few days, they willl shed their skin for the first time. Subsequently, the young are on their own and disperse soon after. There is virtually no parental care. Even though they are now fully independent, they will not be sexually mature for four to five years. (Shea 1997)
Because of the great toll on female lizards during their pregnancy, they are likely to only reproduce every other year. Males are reproductively active every year (Shea 1997).
Relevance to Humans and Ecosystems
Economic Importance for Humans: Positive
In suburban areas, the blotched blue - tongue feasts on snails, slugs and caterpillars (its usual diet) which will be plentiful in any garden or backyard (Jones & Edwards 1998).
Blotched blue-tongued lizard
The blotched blue-tongued lizard (Tiliqua nigrolutea), also known as the southern blue-tongued lizard, is one member of a genus of blue-tongued skinks which is endemic to southeastern Australia. This animal has a fleshy blue tongue which is used to taste the air and scare off potential predators. It is a robust and relatively large member of the skink family (Scincidae) that tends to rely on camouflage and bluff as its primary means of defence. However, if cornered or molested, it can put on an impressive and effective defensive display. If further molested, it will bite, but mainly as a last resort; although the bite is painful due to its powerful jaws, the teeth are blunt and generally do not break the skin. The species is harmless, as all skinks and are inoffensive by nature, often being kept as pets due to its appealing, inquisitive nature and readiness to become tame.
The lizard is about 35 to 50 cm long, and is found in wet and dry sclerophyll forests, montane woodlands and coastal heathlands. It is an omnivore with a diet consisting of leaves, flowers, fruit, slow-moving invertebrates, and small vertebrates. The tail can be dropped (autotomy) when grasped by a predator (like most skinks), but this large skink is much less likely to do so than other members of the skink family.
They are found in southeastern parts of Australia, including Tasmania and the islands of Bass Strait. In the northern parts of their range, such as the central tablelands of NSW, they are generally restricted to highland areas, whereas in southern Victoria and Tasmania, they can be found along the coast. Some herpetologists describe two distinct forms of this species - a highland or alpine form and a lowland or southern form. Specimens from the northern parts of the species range (alpine form) are generally larger, blacker and tend to have more colourful blotches on their backs, which are sometimes pale pink, salmon-pink or orange in colour.
Blotched blue-tongued lizards emerge from brumation in early spring, which is the mating season. These large skinks are viviparous (give birth to live young), with the highland/alpine form giving birth to relatively larger and fewer young (~5-6) compared to the lowland form (~10-12). The young are usually born in autumn, after a relatively long gestation period. They are also relatively long-lived (anecdotally 20 years or more) compared to many of the smaller skink species. They have adapted well to some rural and urban areas, where they can be found living on farms and in gardens where they are an asset, as they love to eat pests like snails, slugs and occasionally rodents.
- Cogger H, (2000) Reptiles & Amphibians of Australia.
- Edwards A, Jones S.M. and Davies N.W. (2005). Patterns of peripheral steroid metabolism vary with sex, season and tissue type in blotched blue-tongued lizards (Tiliqua nigrolutea). Gen. Comp. Endocrinol. 140 14-24.
- Edwards A, and Jones S.M. (2004). Parturition in the blotched blue-tongued lizard, Tiliqua nigrolutea, in captivity. Herpetofauna. 34 113-118.
- Edwards A. and Jones S.M. (2003). Mating behaviour in the blotched blue-tongued lizard, Tiliqua nigrolutea, in captivity. Herpetofauna 33 60-64.
- Edwards A., Jones S.M. and Davies N.W. (2003). Sex and season influence gonadal steroid biosynthetic pathways, end-product production and steroid conjugation in blotched blue-tongued lizards (Tiliqua nigrolutea). Gen. Comp. Endocrinol. 134 131-138.
- Edwards A., Jones S.M. and Davies N.W. (2002). A possible alternative to 17β-estradiol in a viviparous lizard, Tiliqua nigrolutea. Gen. Comp. Endocrinol. 129 114-121.
- Edwards A., Jones S.M., and Wapstra, E. (2002). Multiennial reproduction in females of a viviparous skink, Tiliqua nigrolutea. Herpetologica 58 407-414.
- Gartrell B.D., Girling, J.E., Edwards A., and Jones S.M. (2002). Comparison of noninvasive methods for the evaluation of female reproductive condition in a large viviparous lizard, Tiliqua nigrolutea. Zoo Biol. 21 253-268.
- Atkins, A., Jones S.M. and Edwards A. (2002). Fecal testosterone concentrations may not be useful for monitoring reproductive status in male blue-tongued lizards (Tiliqua nigrolutea: Scincidae). J. Herpetol. 36 106-109.
- Edwards A. and Jones S.M. (2001). Changes in plasma progesterone, estrogen and testosterone concentrations throughout the annual reproductive cycle in female viviparous blue-tongued skinks, Tiliqua nigrolutea, (Scincidae), in Tasmania. Gen. Comp. Endocrinol. 122 260-269.
- Edwards A. and Jones S.M. (2001). Changes in plasma testosterone, estrogen and progesterone concentrations throughout the annual reproductive cycle in male viviparous blue-tongued skinks, Tiliqua nigrolutea, (Scincidae), in Tasmania. J.Herpetol. 35 293-299.