Thick-tailed Gecko Underwoodisaurus milii
The Thick-tailed Gecko is one of the most familiar of the geckoes of southern country-Australia, and one of the most beautiful species in the country. They may be found in a range of habitats, from coastal areas to rocky hills, deserts to dense forest. Despite their name, they are usually found under rocks rather than wood. The name Underwoodisaurus means “Underwood's” and refers to a man by the name of Underwood!
Thick-tailed Geckoes are large and robust by gecko standards, with a maximum snout to vent length of up to around 10cm, but most populations usually only get to around 8cm SVL. Females are usually larger than males, but occasional very large males are sometimes found.
The broad, thick, carrot to turnip-shaped tail is used to store energy, and an inspection of the tail gives a good indication of the health of the animal. The heavier the tail, the better the condition the animal is in. The body is covered in distinct tubercles, some of which are yellow, cream or white and may be scattered randomly over the body or form bands of varying regularity.
These light coloured tubercles contrast sharply with the background colour which ranges from dull browns and purples through to reddish tones.
Occasional hypomelanistic specimens are found, the most extreme of these can be light pink or orange, and other than the eyes they can look quite like albinoes.
Like all geckoes and most skinks, the tail can be cast off when the lizard is scared or when the tail is held, as a predator defense. Original tails usually have a darker background colour than the body, with the light tubercles arranged in clear bands. Regrown tails are shorter and stouter, with smooth skin and irregular, indistinct patterns.
Thick-tailed Geckoes are nocturnal and terrestrial. They are clawed geckoes, meaning they can't climb glass or other smooth surfaces. They are purely carnivorous, preying upon insects, spiders, other arthropods and sometimes even other geckoes such as Marbled Geckoes and Bynoe's Geckoes, which sometimes share their shelter sites and foraging areas. Thick-tailed Geckoes are extremely cold tolerant and may be found active at night even during winter at the southern extreme of their range. They have been found actively hunting at temperatures below 10 degrees Celsius.
During hot days they shelter underground, but during cool weather they take advantage of the sun's heat by resting beneath rocks, especially those which rest upon a rocky base. Aggregations of individuals have often been found, sometimes with over 10 animals sheltering together. Juveniles are particularly prone to aggregating, perhaps to increase their thermal inertia.
They lay leathery-shelled eggs in spring and summer, always with two eggs in a clutch, and multiple clutches may be produced in a season.