Tiliqua nigroluteaBlotched Bluetongue, Southern Bluetongue, Blotched Blue-Tongued Lizard

Geographic Range

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).

Habitat

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).

Physical Description

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
    10.57 to 15.86 oz

Reproduction

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).

Lifespan/Longevity

Behavior

Even though the blotched blue-tongued skink is common in Australia and Tasmania, they are not often seen. They are very secretive and thus have not been frequently observed in their natural habitats. What we do know is that like other reptiles, they bathe in the sun to keep warm. To keep from getting too warm, these skinks scuttle back and forth between shady places and open areas (Cogger 2000, Jones & Edwards 1998).

In order to protect themselves, they use their trademark tongue. As a warning or display, the skink will open its mouth wide and hiss. Many times, the startling blue tongue contrasting the pink mouth will scare the predator away. If not, the lizard will flatten its ribcage and turn onto its side in order to appear larger (Shea 1997).

Food Habits

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)

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).

Economic Importance for Humans: Negative

None

Conservation Status

This species is not considered to be in need of special conservation measures, though a related species, Tiliqua adelaidensis is considered endangered (Cogger 2000).

Other Comments

Even though Tiliqua nigrolutea survive in suburbs, many urban aspects pose a great danger for them. The blue-tongues that live in the suburbs often eat snails and insects carrying human-applied insecticides. The poison sometimes kills the lizard. Another hazard for urban-dwelling lizards is lawn mowers (Shea 1997).

Contributors

Joyce Liu (author), West Windsor-Plainsboro High School, Joan Rasmussen (editor), West Windsor-Plainsboro High School.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

native range

the area in which the animal is naturally found, the region in which it is endemic.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5? N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Cogger, H. July 2000. Reptiles and Amphibians of Australia 6th Edition. Sydney Australia: Chelsea Green Publishing.

Dr Glenn Shea, Research Associate of the Australian Museum., 1997. "Blue-tongued Lizards" (On-line). Accessed 1 August 2002 at http://www.austmus.gov.au/factsheets/blue_tongue_lizard.htm.

Dr. Susan Jones and Ashley Edwards School of Zoology, University of Tasmania, August 21, 1998. "FAUNA OF TASMANIA" (On-line). Accessed (Date Unknown) at http://www.zoo.utas.edu.au/bluetongue.html.