The thorny devil grows up to 20 cm (8.0 in) in length, and can live up to 20 years. Most of these lizards are coloured in camouflaging shades of desert browns and tans. These colours change from pale colours during warm weather and to darker colours during cold weather. These animals are covered entirely with conical spines that are mostly uncalcified.
The thorny devil also features a spiny "false head" on the back of its neck, and presents this to potential predators by dipping its real head. The females are larger than the males. The thorny devil's body is ridged in structure, and this enables the animal to collect water from any part of its body. That water is then conveyed to its mouth.
An intimidating array of spikes cover the entire upper side of the body of the thorny dragon. These thorny scales also help to defend it from predators. Camouflage and deception may also be used to evade predation. This lizard's unusual gait involves freezing and rocking as it moves about slowly in search of food, water, and mates.
Taxonomy and naming
The names of this lizard have been given to it because of its appearance, and two large horned scales on its head complete the illusion of a dragon. Although the name Moloch was formerly used for a deity of the ancient Near East, this name began to be used later in demonology to refer to the fallen angel and Prince of Hell.
The thorny dragon was first described in writing by the biologist John Edward Gray in 1841. While it is the only one contained in the genus Moloch, many taxonomists suspect another species might remain to be found in the wild. The thorny dragon is only distantly related to the similar (morphologically speaking) North American horned lizards of the genus Phrynosoma. This similarity is usually thought of as an example of convergent evolution.
The thorny dragon usually lives in the arid scrubland and desert that covers most of central Australia. For example, it inhabits the Spinifex (triodia) sandplain and sandridge desert in the deep interior and the mallee belt.
The thorny dragon is covered in hard, rather sharp spines that dissuade attacks by predators by making it difficult to swallow. It also has a false head on its back. When it feels threatened by other animals, it lowers its head between its front legs, and then presents its false head.
The diets of thorny dragon mainly subsists on ants, often the Iridomyrmex or the Ochetellus genera. Some reports indicate Iridomyrmex flavipes is its the predominant prey, but this species was renamed Ochetellus flavipes in 1992.
Thorny dragons often eat thousands of ants in one day. They collect moisture in the dry desert by the condensation of dew on their bodies at night. This dew forms on its skin, and then it is channelled to its mouth in hygroscopic grooves between its spines. During rainfalls, capillary action allows the thorny dragon to suck in water from all over its body.
Reproduction and survival
The females lay clutch of three to ten eggs during the September–December season (spring-summer). They put these in a nesting burrow about 30 cm underground. The eggs hatch after about three to four months.
The popular appeal of the thorny dragon is the basis of an anecdotal petty scam. American servicemen stationed in Southwest Australia decades ago (such as during World War II) were supposedly sold the thorny fruits of a species of weeds, the so-called "double gee" (Emex australis), but those were called "thorny devil eggs" as a part of the scam.
Thorny devils have been kept in captivity.
- Browne-Cooper, Robert; Brian Bush, Brad Maryan, David Robinson (2007). Reptiles and Frogs in the Bush: Southwestern Australia. University of Western Australia Press. pp. 46, 65, 158. ISBN 978-1-920694-74-6.
- Pianka, E. R. and H. D. Pianka. 1970. The ecology of Moloch horridus (Lacertilia: Agamidae) in Western Australia. Copeia 1970: 90-103.
- "Australia's Thorny Devil". http://uts.cc.utexas.edu/~varanus/moloch.html. Retrieved 2007-10-31.
- "Australian Ants Online: Genus Ochetellus". Archived from the original on 2007-08-30. http://web.archive.org/web/20070830131921/http://www.ento.csiro.au/science/ants/dolichoderinae/ochetellus/ochetellus_tax_cat.htm. Retrieved 2007-10-31.]
- Bentley, P. J. and F. C. Blumer. 1962. Uptake of water by the lizard, Moloch horridus. Nature 194: 699–700. doi:10.1038/194699a0
- Pianka, E. R. 1997. Australia's thorny devil. Reptiles 5(11): 14-23.