Ackie Monitor (Varanus acanthurus)
Published: February 27, 2021
Last Updated: November 8, 2023
The ackie (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, brown, or black-brown with yellow, cream, or red spotting. The head typically features three pale 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)
It is our belief here at ReptiFiles that reptiles are more complex than they have been long assumed to be, and no species can be appropriately described as simple or stupid. However, monitor lizards are well known to be especially complex and intelligent among reptiles. They have mammal-like features in their physiology (Horn & Visser, 2007), and have demonstrated exceptional intelligence even in captivity. Although some reptile species will tolerate minimalistic husbandry conditions, monitors will not. Keep this in mind as you consider the ackie monitor as a pet.
Ackie Monitor Care Guide — Table of Contents:
- Introduction to Ackie Monitors
- Varanus acanthurus Subspecies
- Shopping List: Supplies You Will Need
- How to Select and Buy a Pet Ackie Monitor
- Enclosure Size & Roommates
- Lighting & UVB Requirements
- Heating Requirements
- Humidity Requirements
- Substrate Options
- Environmental Enrichment: Decorating the Enclosure
- Feeding Your Ackie Monitor
- Handling Tips & Behavioral Notes
- General Health Guide
- Additional Resources
Special thanks to John Aromando, Jeff Easter, Steven Bowman, David Archer, Linnea Saphia, and Stefan Windsor for their contributions to this guide.