Spiny-tailed monitor

The spiny-tailed monitor, a somewhat small monitor lizard, can attain a total length of up to 70 cm (27 in), although there are unconfirmed reports of wild individuals growing up to 34 inches. The tail is about 1.3-2.3 times as long as the head and body combined. The upper side is a rich, dark brown and painted with bright-yellowish to cream spots, which often enclose a few dark scales. Its tail is round in section and features very spinose scales. There are 70-115 scales around the middle of the body. The spiny-tailed monitor is distinguished from the similar-looking species V. baritji and V. primordius by the presence of pale longitudinal stripes on the neck. == Distribution and habitat ==

This arid-adapted == Subspecies and taxonomy ==

The spiny-tailed monitor is part of an Indonesian and Australian radiation of dwarf monitor lizards, the subgenus Odatria. • V. a. insulanicus of Groote Eylandt and the islands of the Wessel group The taxonomic status of the three subspecies is uncertain. In 2006, the results of a study on the mtDNA of Australian monitors were published, according to which the two continental subspecies do not form natural (monophyletic) taxonomic entities. V. a. insulanicus was found to be monophyletic, but it is more closely related to V. baritji than to other V. acanthurus. Therefore, V. a. insulanicus might represent a distinct species. Wilson and Swan (2010) still accept V. a. insulanicus as a valid subspecies of V. acanthurus, which is easily distinguished from other spiny-tailed monitors by its dark colouration and more banded pattern. == Ecology ==

Spiny-tailed monitors are diurnal, typically solitary ground-dwellers. This species is most often found in its shelter, mainly under rock slabs, wedged among boulders or in rock crevices, and in burrows. Only rarely do they hide in spinifex. Small lizards such as skinks, geckos, dragon lizards, or possibly smaller monitor lizards are also eaten, making up about a third of its diet, as well as marsupial joeys. Approximately 70% of its water requirement comes from food. A varied diet rich with different vertebrate and invertebrate prey (such as Dubia roaches, crickets, mealworms, eggs, shrimp, and, on a monthly basis, rodents) is important to the health of captive spiny-tailed monitors, as they naturally have a wide range of prey in the wild. == Reproduction ==

There are a number of methods of sexing ackie monitors, although the hemipenal transillumination technique is generally considered to be the easiest and most accurate. Sex can also be guessed using visual markers, but it is typically not nearly as accurate. Male ackie monitors are generally larger, have blockier heads, and have grippy scales on the underside of their tail. Females are generally smaller with narrower, pointier heads, and smooth scales under their tail. In captivity, a clutch consists of up to 18 eggs. The young hatch after three to five months of incubation, and measure 15 cm (6 in). The knowledge on reproduction in the wild is sparse. Males most likely mature at 30 cm (12 in) snout-vent length, females mature at 25–36 cm (10–14 in) snout-vent length. Ovulation occurs in August and November. The eggs are deposited in self-dug tunnels. == References ==