The ackie monitor (also known as ridgetail(ed) monitor, spiny-tailed monitor, or ackies dwarf monitor) is a diurnal, terrestrial monitor lizard native to the west, north, and center of northern Australia, including some islands off the northern coast. They prefer arid and seasonally dry habitats with lots of rocks, boulders, and spinifex grass, and often shelter in crevices between the rocks as well as burrows underneath them.                                                                              

Ackie monitors are long, slender monitors with a snakelike tongue, sharply tapered snout, somewhat rounded body, relatively short legs, and a whiplike tail. The body is typically red with yellow/cream spotting or brown with yellow/cream spotting. The head typically features three light-colored stripes running from the face to the neck. The tail is long and covered in heavily keeled scales in a pattern of alternating light and dark rings, giving it a spiny appearance and function. The underside is typically pale and patternless.

As a dwarf monitor under the subgenus Odatria, ackies are fairly small even as fully-grown adults: sources generally agree that adult ackies are typically around 2’/0.6m long, but they have been reported as small as 17.3”/44cm and as large as 30”/76cm. Males are typically somewhat larger than females. It is reported that red ackies generally grow larger and have relatively longer tails than other localities (Kuhn & Julander, 1999). Ackies in general are known to live for at least 15 years with good care.

There are three subspecies of Ackie Monitor:

• Varanus acanthurus acanthurus
• Varanus acanthurus brachyurus
• Varanus acanthurus insulanicus

Fun Facts About Ackie Monitors:

• The name “ackie monitor” is derived from the pronunciation of their Latin name, ACK-an-thur-us.
• In the wild, color is generally correlated with the color of the soil and rocks in an ackie monitor’s habitat as a form of camouflage.
• Ackie monitors use their spiny tails to protect themselves from predators. They will wedge themselves into a tight space and then block the entrance with their tail. (Eidenmuller, 2007)