| Bobtail Skink | |
|---|---|
| Tiliqua rugosa rugosa | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Family: | Scincidae |
| Genus: | Tiliqua |
| Species: | T. rugosa |
| Binomial name | |
| Tiliqua rugosa (Gray, 1825)[1] |
|
| Subspecies | |
|
4, see text |
|
| Synonyms | |
|
Trachydosaurus rugosus |
|
Tiliqua rugosa is a short-tailed, slow moving species of blue-tongued skink found in Australia. Three of the four [2] recognized subspecies are found only in Western Australia, where they are known collectively by the common name bobtail.[3] The name shingleback is also used, especially for T. rugosa asper, the only subspecies native to eastern Australia.
T. rugosa has a heavily armoured body and can be found in various colours, ranging from dark brown to cream. It has a short, wide stumpy tail that resembles its head and may confuse predators. The tail also contains fat reserves, which are drawn upon during hibernation in winter. This skink is an omnivore that eat snails and plants and spends much of its time browsing through vegetation for food. It is often seen sunning itself on roadsides or other paved areas.
Apart from bobtail and shingleback a variety of other common names are used, including stump-tailed skink, bogeye, pinecone lizard and sleepy lizard.[2]
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The species was first described by John Edward Gray in 1825 as Trachydosaurus rugosus.[2] It has since been reclassified as Tiliqua rugosa. Some herpetologists claim this species has more common names than any other lizard.[4]
Four subspecies are currently recognized:[2]
The species is widely distributed in arid to semi-arid regions of southern and Western Australia. The range extends from Shark Bay, Western Australia, across the southern-most regions of the country to the coast, then north into Queensland. Four subspecies are found in Western Australia, including one at Rottnest Island. It also occurs in the eastern states of Victoria and New South Wales, but does not reach coastal areas.[8]
The habitat of the species includes shrubland and desert grassland to sandy dunes. These skinks are well known, due to a preference for sun basking and open areas, and are often seen along roadsides or other cleared areas in its range.[9]
Tiliqua rugosa has a heavily armoured body and can be found in various colours, ranging from dark brown to cream.[4] Its total length seldom exceeds 18 or 25 inches, but it is a very heavy-bodied lizard for its length.[4]
It has a triangular shaped head, and a bright blue tongue.[4] Its short stumpy tail is similar in shape to its head. This possibly evolved as a defence mechanism against predators and has led to the common name of "two-headed skink".[4] Their short tail also contains fat reserves, which the lizard lives upon during hibernation in winter.[4] Unlike many skinks, shinglebacks do not exhibit autotomy and cannot shed their tails [10].
Tiliqua rugosa is an omnivore that eat snails, insects, carrion, vegetation and flowers. The species was once preyed upon by dingos, Australian pythons such as Morelia spilota, and local peoples; a threat is now more likely to come from large introduced feral species such as foxes and cats.[11] They have been know to eat human food such as sausage and chicken as well as fruits such as banana and passionfruit.
Tiliqua rugosa is a viviparous skink, giving birth to broods of 1 to 4 relatively large offspring.[4] Unlike most lizards, the species tends to be monogamous extending outside the breeding season of September through November; such pairs have been known to return to each other every year for up to 20 years.[4][12]
Upon being born, the newborn young immediately consume their afterbirth.[4] The young stay with their parents for several months before moving on, however they remain in close proximity forming a colony of closely related skinks.[4]
The male of a monogamous pair eats less while parenting, remaining alert and ready to give an alarm.[4]
The hearing of T. rugosus, can be measured at the round window as cochlear microphonics and summating potential (of the cochlea), and compound action potential (of the auditory nerve). These indicate a probable best hearing range of 750–3000 Hz. When pairs of sine wave tone bursts were sounded, the amplitude and latency of the neural response to the second tone burst were greatly increased. This may indicate a greater (behavioural) sensitivity to a second sound. The summating potential was very sensitive to season, increasing ten-fold during spring.
Single unit recordings from the auditory nerve show both spontaneous and nonspontaneous responses. The spontaneous fibers exhibited multimodal interval histograms and responded to a tone burst by an initial rate increase, an after-inhibition, and a rebound. Tuning curves show peak sensitivity between 700 Hz and 3 kHz. A marked seasonal dependence on the number of responsive fibers correlates well with the increase of summating potential found to occur during early spring. The absolute sensitivity is quite high, with thresholds below 25 db sound pressure level. The most sensitive fiber respond to the rustle of clothing a few feet away.[13][14]