Spiny-tailed Skinks of Shark Bay
What do they look like?
Spiny-tailed skinks are stout lizards that grow up to 30 cm long. They get their name from their flat tail, which is not only relatively short – only a third of their body length – but equipped with strong spines that are used to get a grip in their rocky home. Their strong legs and long toes also help stop them from falling to the ground. Their skin is well adapted to their habitat, being thick and covered with rough-edged scales to minimise water loss in the hot desert sun. Their colour ranges from olive-brown to reddish-brown, with some individuals having paler scales with dark edges. Their underbelly is white or creamy yellow.
Where do they live?
Spiny-tailed skinks live within deep crevices or under boulders in stony hills. They are also known to occupy hollow trees. Two subspecies of spiny-tailed skink are found in Shark Bay. The western spiny tailed skink (Egernia stokesii badia), also known as a gidgee skink, is found from the mid-west coastal region and Dirk Hartog Island inland to central Western Australia and the northern wheatbelt. It may be spotted in Francois Peron National Park. Another spiny-tailed skink (Egernia stokesii stokesii) is found in Edel Land and on Baudin Island, a small rocky island in the south-western side of Henri Freycinet Harbour in the Shark Bay World Heritage Area. It is also found in the Houtman Abrohlos Islands, off the coast of Geraldton.
The skinks are active during the day, using the sticky mucous on their flat, oval tongue to trap spiders and insects such as grasshoppers. They stick close to home, hunting and basking near the safety of their crevices. Unusual for reptiles, the skinks live in colonies of up to 16 lizards. Everyone in the same colony defecates in the same spot near their basking area, accumulating a pile of poo used to mark their territory. These tidy lizards are not only able to tell which is their pile, and which belongs to another colony – they can tell who is a relative and who is not! Studies have shown that females and their young can identify each other through the use of tongue flicks. This helps the female protect her own young during their crucial first days of life, and may also prevent interbreeding with close relatives.
How do they breed?
Spiny-tailed skinks reach maturity by the age of two and can live up to twenty-five years! Unlike most skinks they bear live young, averaging five per litter. The embryos are nourished within the female by a placenta-like organ and born in February or March. Young spiny-tailed skinks are just 6 cm long!
Any threats to their survival?
The western spiny-tailed skink is listed as a threatened species
due to a reduction in its habitat across the bulk of its range, the northern wheatbelt of Western Australia. Dirk Hartog Island is soon to become a national park, which will give this skink greater protection against dangers such as the possible introduction of rats. The other skink (Egernia stokesii stokesii
) is common on Baudin Island, where the impact of fires and introduced predators could be devastating. Baudin Island is a nature reserve with the highest level of protection under Western Australian law. For more information about Western Australian wildlife check out the WA Museum Fauna Base
to download a printable PDF of this fact sheet.