Tiliqua rugosa

Tiliqua rugosa
Eastern shingleback
Conservation status
Least Concern  (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Family:	Scincidae
Genus:	Tiliqua
Species:	T. rugosa
Binomial name
Tiliqua rugosa (Gray, 1825)
Subspecies
T. r. rugosa T. r. asper T. r. konowi T. r. palarra
Distribution of Tiliqua rugosa
Synonyms
Trachydosaurus rugosus

Western shingleback

Rottnest Island shingleback

Tiliqua rugosa is a type of lizard mostly called the shingleback skink, shingleback lizard, or bobtail lizard. It has a short tail and moves slowly. This lizard is a kind of blue-tongued skink and lives only in Australia. There are four kinds (subspecies) of this lizard. Three live in Western Australia, where people often call it bobtail. The fourth kind, called T. rugosa asper, lives in eastern Australia and is called the eastern shingleback.

This lizard has many other names in different parts of Australia. Some of these names are two-headed skink, stumpy lizard, stumpy-tailed lizard, pinecone lizard, bogeye or boggi, and sometimes sleepy lizard. The Noongar Indigenous Australians call it yoorn their language.

The lizard has a short, wide tail that looks like its head. This helps to confuse animals that want to eat it. The tail also stores fat, which the lizard uses in winter when it is less active. In winter, the lizard goes into a state like hibernation called brumation. During this time, it needs water every day but can go without food. The shingleback lizard eats both animals and plants. It likes to eat snails and plants and spends a lot of time looking for food in plants. Near people’s homes, it is often seen lying in the sun on roads or paved places.

Etymology and taxonomy

The lizard was first named Trachydosaurus rugosus by John Edward Gray in 1825.. Now, it is called Tiliqua rugosa. Some experts say this lizard has more common names than any other lizard.

Subspecies

Their are four subspecies of Tiliqua rugosa:

• Tiliqua rugosa asper: eastern shingleback – eastern Australia (New South Wales, Queensland, South Australia and Victoria)
• T. rugosa rugosa: bobtail or western shingleback – Western Australia
• T. rugosa konowi: Rottnest Island bobtail or Rottnest Island shingleback – Rottnest Island, Western Australia
• T. rugosa palarra: northern bobtail or Shark Bay shingleback – Shark Bay, Western Australia

Distribution and habitat

This lizard lives in many dry and semi-dry areas of southern and western Australia. Its range goes from Broome, Western Australia, across the southern parts of the country to the coast, and then north into Queensland. Four types (subspecies) live in Western Australia, including one on Rottnest Island. The lizard also lives in the eastern states of Victoria and New South Wales but does not live near the coast in these states.

The lizard lives in places like shrub lands, eucalyptus forests, desert grasslands, and sandy dunes. It often hides under low plants in the bush. Because it is cold-blooded, it likes to sit in the sun in open areas. You can often see it along roadsides, edges of fields, or other open places. Each lizard usually lives in an area about 4 ha (9.9 acres) and can move up to 500 m (1,600 ft) in one day.

These lizards usually stay in the same home area for many years. Sometimes, several lizards share the same burrow (a hole or shelter in the ground). When it gets hotter and drier, they tend to share burrows more. In spring, when there is enough food and it is mating season, male lizards may have overlapping home areas. This can cause them to be territorial and sometimes fight.

Description

Shingleback lizard

Tiliqua rugosa has a strong, armored body and can be many colors, from dark brown to cream. Its body length (from snout to the base of the tail) is usually between 260–310 mm (10–12 in). It has a heavy body for its size. Its eyes are small and colored reddish-brown and grey.

The lizard has a triangular head and a bright blue tongue inside a bright pink mouth. Its short, thick tail looks like its head. This helps confuse animals that want to eat it. The tail also stores fat, which is why it is sometimes called the "two-headed skink." Unlike many other skinks, this lizard cannot drop its tail to escape danger.

These lizards usually live 10 to 15 years, but some have lived up to 50 years in the wild.

The lizard sheds its skin all at once, including the skin over its eyes. This can take several hours, and the lizard rubs against things to help remove the old skin.

Shed skin, 27 cm (11 in) long, head on right of image

Male and female lizards look different. Males are usually stockier and have bigger heads, but females usually grow larger than males.

Diet

Front view

Tiliqua rugosa is an omnivore, which means it eats both animals and plants. It eats snails, insects, dead animals, plants, and flowers. Because it moves slowly, it usually eats other slow animals. This may be why it likes plants more than other blue-tongue skinks. It has strong jaws that can easily crush snail shells.

Since these lizards live near people, they sometimes eat human food like sausage, chicken, and fruits such as strawberries, bananas, and passionfruit.

Behaviour

Tiliqua rugosa lives a quiet life and is usually peaceful with other lizards. But they are territorial and can act aggressively toward other lizards that enter their area. They have home areas that they keep for a long time and can tell other lizards apart by smell. Family members who live nearby and share burrows do not fight. However, unfamiliar male lizards may fight each other sometimes. Studies show that male lizards without mates are more likely to be aggressive to other males. They are called floating males because they move through many home areas that have male lizards living there. Tiliqua rugosa does not take care of its babies, so the fact that they usually have one mate (monogamy) only helps before they mate.

In captivity

The shingleback skink is a popular pet in Australia. They are calm and easy to feed and care for. In some states, you may need a permit to keep one. If they feel scared or threatened, they might bite people. Their bite is not poisonous but can hurt like other animal bites and may cause swelling or bruises.

Threat display

Threat display and predators

This lizard used to be hunted by dingos, Australian pythons like Morelia spilota, and Aboriginal Australians. Now, the main threats come from large wild animals brought to Australia, such as foxes and cats. In Western Australia’s bush areas, birds like brown falcons and laughing kookaburras, and big snakes like eastern brown snakes, red-bellied black snakes, and mulga snakes often hunt this lizard.

Ticks and nematodes often live on this lizard by attaching under its scales or in its ears. One type of tick, the kangaroo soft tick Ornithodoros gurneyi, sometimes lives on Tiliqua rugosa because they share the same bushes and leaf litter where red kangaroos and wallabies rest on hot days. Red kangaroos are the main host for these ticks, but young ticks can also live on the shingleback lizard and grow to adults. The lizard may help spread these ticks because it moves over a large area where different animals meet.

Tiliqua rugosa has many ways to protect itself from predators. It often opens its mouth wide and shows its blue tongue while making a loud hissing sound. If the danger continues, it can give a strong bite to defend itself.

Reproduction

Tiliqua rugosa is a live-birth lizard (viviparity), which means its babies are born alive instead of hatching from eggs like most other lizards. Pregnancy and giving birth are very hard for the mother. The babies together weigh about 27% of the mother's weight.

The mother usually has one to four babies, but most often two or three. The babies are quite big, which helps them survive better. Females possess a well-developed placenta with which they feed their unborn young. The mother has a special placenta to feed the babies before they are born.

Unlike many other lizards, these lizards usually have one mate (monogamous) and meet again in pairs from September to November before the breeding season. Some pairs stay together every year for up to 20 years. The breeding season is from December to April, and the pregnancy lasts about 3 to 5 months.

When the babies are born, they eat their afterbirth right away. They stay close to their parents for several months before living on their own. Even after that, they stay near each other, forming a group of related lizards.

The male in a pair eats less while helping take care of the babies. He stays alert and ready to warn of danger. He follows the female to protect her from other males while she looks for food.

Social life

Tiliqua rugosa at Sparrow Hill, near Canberra

Forming a pair with one mate is very important in the life of this lizard. The male has a great sense of direction and can follow the female many times, even when it is not mating season. If one lizard in the pair dies, the other may show signs of sadness or stay near the lost partner for a while.

Monogamy (having one mate) helps the female lizards more than males. Because of this, it is rare for females to have many mates (polyandry), but males sometimes have more than one mate (polygyny). Females like males who pay attention to them and choose who to mate with. Males must show they care by following the female for a few weeks before she agrees to mate. Because of this, females often stay with the same male for many years. They like knowing the male will be caring and attentive. If a male is less caring one year, the female might choose a different mate the next year.

There are many reasons why monogamy is common in bobtail lizards. First, having two parents helps take better care of the babies. Both parents can watch, protect, and find food for the young. Also, it is easier for males to guard one female’s home area. If a male has many mates, it is hard to protect all their areas from other males, which wastes time and energy.

Sometimes, females mate with males outside their pair, which can lead to bigger litters. But in these cases, the female gets less attention from the male. That is why most bobtail lizards prefer monogamy.

Hearing, smell and sight

Hearing

The bobtail lizard can hear sounds best around 1000 Hz. Scientists measure their hearing by looking at how parts of their ear and auditory nerve respond to sounds. Earlier ideas that their hearing changed with the seasons were found to be wrong; it was actually because of how they reacted to anesthesia during tests. Their hearing is very sensitive, almost as good as humans, especially between 200 Hz and 4,500 Hz.

Smell (Olfaction)

The sense of smell is very important for these lizards, especially to help them avoid danger. They live in bush areas where fires can happen often, so they need to smell smoke quickly. Studies showed that when there is smoke, the lizards become more active, moving around and flicking their tongues to smell better. This shows they can detect fires using their sense of smell.

Sight (Visual Perception)

Bobtail lizards can find their way back home even if they are moved away from their usual area. They do this by using special visual clues from light patterns and the Earth's magnetic field, like a natural compass. This helps them know which direction to go. But this ability works only if they are moved less than about 800 m (2,600 ft) away. If they are moved farther, they get lost and cannot find their way home.

Conservation status

The bobtail lizard (Tiliqua rugosa) is listed as Least Concern on the IUCN Red List, which means it is not in danger of disappearing soon. In Australia, it is a protected animal and can only be taken out of the country with a special government permit. However, trading or bringing this lizard into other countries is usually not illegal. The number of these lizards is steady, and there are mostly no big dangers to them. But one type of this lizard, called T. r. konowi, which lives on Rottnest Island, is considered Vulnerable, meaning it faces some risk of becoming endangered.

Other sources

• Lysaght, Gary-Jon; Corvo, Shannon (19 February 2020). "Fleas and ticks may be creating new sub-species of shingleback lizards". ABC News. Australian Broadcasting Corporation. Retrieved 20 February 2020.