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'{{speciesbox | name = Spiny-tailed monitor | image = Spiny-tailed-monitor.jpg | status = NE | status_system = IUCN3.1 | genus = Varanus | subgenus = Odatria | species = acanthurus | authority = [[George Albert Boulenger|Boulenger]], 1885 | range_map = Spiny-tailed Monitor.png | range_map_caption = Distribution of the spiny-tailed monitor}} The '''spiny-tailed monitor'''<ref name="wilsonswan2010"/> (''Varanus acanthurus''), also known as the '''ridge-tailed monitor'''<ref name="cogger2000"/> or '''Ackies dwarf monitor''',<ref>[http://cincinnatizoo.org/blog/animals/ackies-dwarf-monitor/ Cincinnati Zoo & Botanical Garden]</ref> is an [[Australia]]n species of lizard belonging to the genus of [[monitor lizard]]s (''Varanus''). == Description == The spiny-tailed monitor, a medium-sized monitor lizard, can attain a total length of up to 70&nbsp;cm (27&nbsp;in). The tail is about 1.3-2.3 times longer than head and body. 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.<ref name="cogger2000"/> The spiny-tailed monitor is distinguished from the similar-looking species ''[[Varanus baritji|V. baritji]]'' and ''[[Varanus primordius|V. primordius]]'' by the presence of pale longitudinal stripes on the neck.<ref name="wilsonswan2010"/> == Distribution and habitat == This arid-adapted<ref name="dryden2004"/> lizard is found in northern [[Western Australia]], in the [[Northern Territory]] and in the eastern and northeastern parts of [[Queensland]].<ref name="dryden2004"/> The spiny-tailed monitor inhabits is associated with arid rocky ranges and outcrops.<ref name="wilsonswan2010"/><ref name="cogger2000"/> == Subspecies and taxonomy == The spiny-tailed monitor is part of an exclusively Australian [[radiation]] of small monitor lizards, the subgenus ''Odatria''.<ref name="böhme2003"/><ref name="fitchetal2006"/> In the past, three subspecies of ''V. acanthurus'' were recognised: The continental subspecies ''V. a. acanthurus'' and ''V. a. brachyurus'', and ''V. insulanicus'', that only inhabits [[Groote Eylandt]] and the islands of the [[Wessel Islands|Wessel group]].<ref name="wilsonswan2010"/><ref name="cogger2000"/> 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 proven to be monophyletic, but it is more closely related to ''[[Varanus baritji|V. baritji]]'' than to other ''V. acanthurus''. Therefore, ''V. a. insulanicus'' might represent a distinct species.<ref name="fitchetal2006"/> 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.<ref name="wilsonswan2010"/> [[File:Varanus acanthurus25.JPG|thumb|left|Two spiny-tailed monitors at the Cincinnati Zoo]] [[File:Ackies Dwarf Monitor.jpg|thumb|left]] == Ecology == Spiny-tailed monitors are diurnal, solitary ground-dwellers. This species is most often found in its shelter, mainly under rock slabs, boulders or in rock crevices. Only rarely do they hide in spinifex.<ref name="cogger2000"/> As the spiny-tailed monitor has a lower level of activity compared to other monitor lizards, as well as a lower metabolic rate, it is often found in its hideout at day, and most likely it is a sit-and-wait-predator. They prey mainly on insects, especially [[orthopteran]]s, beetles and cockroaches, and on small lizards such as skinks, geckoes or small [[Agamidae|dragon lizards]]. Less often, this species feeds on other insects, spiders, snails or young marsupials. Approximately 70% of its water requirement comes from food.<ref name="dryden2004"/> == Reproduction == In captivity, a clutch consists of up to 18 eggs. The young hatch after three to five months of [[Egg incubation|incubation]], and measure 15&nbsp;cm (6&nbsp;in). The knowledge on reproduction in the wild is sparse. Males most likely mature at 30&nbsp;cm (12&nbsp;in) snout-vent length, females mature at 25–36&nbsp;cm (10–14&nbsp;in) snout-vent length. Ovulation occurs in August and November. The eggs are deposited in self-dug tunnels.<ref name="dryden2004"/> == References == {{commons category|Varanus acanthurus}} <references> <ref name="böhme2003">Böhme W. 2003. ''Checklist of the living monitor lizards of the world (family Varanidae)''. Zoologische Verhandelingen 341, pp 3–43.</ref> <ref name="cogger2000">Cogger H. 2000. ''Reptiles & Amphibians of Australia''. Ralph Curtis Publishing, Sanibel Island, Florida. ISBN 0-88359-048-4. Pp 359-361.</ref> <ref name="dryden2004">Dryden G. 2004. ''Varanus acanthurus''. In: ''Varanoid Lizards of the World'' (Hrsg. Pianka ER, King DR), pp 298-307. Indiana University Press, Bloomington & Indianapolis. ISBN 0-253-34366-6.</ref> <ref name="fitchetal2006">Fitch AJ, Goodman AE, Donnellan SC. 2006. ''A molecular phylogeny of the Australian monitor lizards (Squamata:Varanidae) inferred from mitochondrial DNA sequences''. Australian Journal of Zoology 54, p 253-269.</ref> <ref name="wilsonswan2010">Wilson S, Swan G. 2010. ''A complete guide to reptiles of Australia''. New Holland Publishers, Sydney, Auckland, London, Cape Town. ISBN 978-1-877069-76-5. P 392.</ref> </references> {{Varanoidea}} {{DEFAULTSORT:Spiny-Tailed Monitor}} [[Category:Monitor lizards]] [[Category:Reptiles of Western Australia]] [[Category:Reptiles of Australia]] [[Category:Animals described in 1885]]'