R
Species Profile

Red Ackie Monitor

Varanus acanthurus

Small goanna, big attitude-spiny tail!
Fivespots/Shutterstock.com

Red Ackie Monitor Distribution

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Endemic Species
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Found in 1 country

Ackie Monitor

At a Glance

Wild Species
Also Known As Ackie monitor, Ackie, Ridge-tailed monitor, Spiny-tailed monitor, Ackie goanna
Activity Diurnal+
Lifespan 8 years
Weight 0.9 lbs
Status Least Concern
Did You Know?

"Red ackie" is a color form/locale within the spiny-tailed monitor lizard, not a separate species (monitor lizard family).

Scientific Classification

A small-to-medium Australian monitor lizard commonly kept in captivity; “red ackie” refers to individuals/populations with pronounced red-orange coloration. It is a diurnal, terrestrial-to-semi-fossorial predator with a distinctive spiny tail.

Kingdom
Animalia
Phylum
Chordata
Class
Reptilia
Order
Squamata
Family
Varanidae
Genus
Varanus
Species
Varanus acanthurus

Distinguishing Features

  • Stout-bodied dwarf monitor with a distinctly spiny, ringed tail
  • Reddish to orange-red body coloration in the ‘red ackie’ form (pet trade term)
  • Diurnal basking behavior and strong burrowing/crevice use
  • Typical monitor traits: forked tongue, alert head posture, clawed limbs

Physical Measurements

Length
2 ft 3 in (1 ft 12 in – 2 ft 6 in)
Weight
1 lbs (1 lbs – 2 lbs)
Tail Length
1 ft 4 in (1 ft 1 in – 1 ft 6 in)
Top Speed
9 mph
running
Venomous

Appearance

Primary Colors
Secondary Colors
Skin Type Dry, keratinized reptilian scales; granular/pebbled dorsal scalation with strongly enlarged, keeled, spiny caudal scales forming a 'thorny' tail.
Distinctive Features
  • "Red ackie" is a color form/locale of Varanus acanthurus, not a separate taxon.
  • Adult size typically ~60-76 cm total length (SVL commonly ~23-30 cm); tail comprises ~55-65% of total length (species accounts/field measurements reported in Varanus literature).
  • Distinctive spiny tail: enlarged keeled caudal scales used in defense and as a brace in crevices.
  • Dwarf-monitor build relative to larger Varanus: compact body, robust limbs, long digits, strong claws for digging.
  • Arid-zone ecology: diurnal, terrestrial-to-semi-fossorial; shelters in burrows, rock crevices, and under slabs; often basking near retreat entrances (documented in field observations of V. acanthurus).
  • Head typically wedge-shaped with large eyes; tongue long and deeply forked (chemosensory foraging typical of Varanus).

Sexual Dimorphism

Dimorphism is subtle. Males average more robust with broader heads/necks and a thicker tail base with hemipenal bulges; females tend to be slightly smaller-bodied with a narrower head and slimmer tail base.

  • Broader, more angular head and thicker neck musculature
  • Thicker tail base; paired hemipenal bulges visible in mature males
  • Often slightly larger overall mass at comparable lengths
  • Narrower head and neck profile
  • Slimmer tail base without hemipenal bulges
  • Often slightly shorter and lighter at comparable ages

Did You Know?

"Red ackie" is a color form/locale within the spiny-tailed monitor lizard, not a separate species (monitor lizard family).

Adults are typically ~60-70 cm total length (tail included); it's a "dwarf monitor" compared with many Varanus that exceed 1-2 m TL (e.g., perentie, lace monitor).

The scientific species name means "spiny tail," referencing the enlarged, keeled tail scales used in defense and bracing.

Clutches are commonly around ~6-12 eggs (reported ranges extend higher in some accounts), usually laid in burrows/termite mounds; hatchlings emerge in the wet season in many regions (field natural history syntheses).

This monitor lizard is strongly diurnal-most active in daylight-using basking to reach high operating body temperatures typical of monitor lizards (varanoid physiology summaries).

Wild habitat use centers on rocky outcrops, spinifex grasslands, and firm soils where it can excavate deep retreats (Australian field guides).

It's a frequent captive monitor because it stays relatively small, is highly food-motivated, and uses complex digging/rock-climbing behaviors in enriched enclosures (husbandry literature).

Unique Adaptations

  • Spiny, keeled tail scales: provide protection and traction; function in defense and in "anchoring" within crevices-diagnostic for the acanthurus group.
  • High-performance chemosensory system: deeply forked tongue + Jacobson's organ enables precise prey-trail sampling, a hallmark adaptation of monitor lizards.
  • Strong limbs and claws: adapted for digging firm arid soils and climbing rocky substrates; supports its terrestrial-to-semi-fossorial lifestyle.
  • Arid-zone water economy: uses burrows/rock shelters to buffer heat and dehydration; behaviorally regulates exposure to reduce water loss (common in desert reptiles).
  • Relatively small adult size among monitors ("dwarf monitor"): enables exploitation of prey-rich microhabitats (spinifex, rocky rubble) less accessible to larger varanids.

Interesting Behaviors

  • Diurnal bask-and-hunt cycle: emerges to bask, then actively forages with rapid head movements and tongue-flicking to sample scents (vomeronasal tracking typical of Varanus).
  • Semi-fossorial engineering: digs and maintains burrows; will also wedge into rock crevices, often choosing retreats with stable temperatures/humidity.
  • Tail bracing: uses the stiff, spiny tail as a prop when backing into cracks or burrows, helping resist extraction by predators.
  • Defensive displays: hissing, body inflation, lateral flattening, and tail-whipping; will retreat quickly to a refuge rather than stand and fight when possible.
  • Opportunistic predation: stalks and pounces on insects and other small prey; can excavate to reach invertebrates or small vertebrates in soil/leaf litter.
  • Seasonal activity shifts: reduces surface activity during extreme heat or cool periods, relying more on burrow microclimates (arid-zone behavioral ecology pattern).

Cultural Significance

In Australia, goannas (monitor lizards) are important in Aboriginal culture as totems, ancestors, and seasonal signs. The red ackie (Varanus acanthurus) fits this role in arid, rocky country and is a symbol for pet keeping and arid-habitat education.

Myths & Legends

Goanna Dreaming stories (various Aboriginal nations): goanna as an ancestral being whose travels shape features of the landscape; goanna tracks, rock formations, and water places are often interpreted through these narratives.

Fire-and-goanna traditions (recorded in multiple Aboriginal story collections): tales where goanna is involved in the keeping, stealing, or sharing of fire-sometimes hiding embers in a burrow or carrying fire between camps.

Totemic goanna lore: in many regions, goanna is a clan totem associated with particular tracts of country; ceremonies and kinship rules tie people to goanna sites and songs.

Hunting knowledge narratives: oral traditions describing goanna as a clever, watchful quarry that retreats into rock holes and burrows-stories used to teach patience, tracking, and respect for animal refuges.

Conservation Status

LC Least Concern

Widespread and abundant in the wild.

Population Stable

Protected Under

  • CITES Appendix II (Varanus spp. international trade controls)
  • Australia: Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) - regulates export/import and wildlife trade of native species
  • Australian state/territory wildlife legislation (native reptile protection; collection/keeping requires permits, varies by jurisdiction)

Life Cycle

Birth 10 hatchlings
Lifespan 8 years

Lifespan

In the Wild
4–15 years
In Captivity
10–20 years

Reproduction

Mating System Polygynandry
Social Structure Solitary
Breeding Pattern Seasonal
Fertilization Internal Fertilization
Birth Type Internal_fertilization

Solitary adults; during the breeding season males roam and compete for access to receptive females, mating via internal copulation. Encounters are brief with no pair bond; females lay clutches and provide no parental care beyond oviposition.

Behavior & Ecology

Social Solitary Group: 1
Activity Diurnal, Matutinal, Vespertine
Diet Insectivore Termites (especially mound-associated termites and alate emergences)
Seasonal Hibernates

Temperament

Predominantly solitary, semi-fossorial predator; relies on rapid retreat to burrows/rock crevices (Pianka 1986).
Wary and alert; defensive behaviors include gaping, biting, and tail-whipping when cornered.
Seasonal breeding increases male-male antagonism; ritualized threat displays and combat may occur (Pianka 1986).
HUBS: Individuals vary from highly defensive to tolerant/curious with habituation in captivity.
Reported adult total length commonly ~60-70 cm (Pianka 1986); captive longevity frequently reported ~15-20+ years (Bartlett & Bartlett 2001; de Vosjoli 2004).

Communication

hissing
forceful expiratory exhalations during threat/handling
chemical sampling via frequent tongue-flicking Prey, conspecific trails, reproductive state
visual threat displays: raised posture, lateral compression, gaping, head/neck extension
tactile/physical signaling: chasing, grappling, biting during disputes or breeding
tail use: tail-whipping and body positioning to deter approach Spiny tail as defensive signal
deposition of feces/urates around shelters Likely incidental cues; may function as chemical information

Habitat

Biomes:
Savanna Tropical Dry Forest Desert Hot
Terrain:
Rocky Sandy Plains Plateau Hilly
Elevation: Up to 2952 ft 9 in

Ecological Role

Insectivorous mesopredator in arid and semi-arid Australian ecosystems (often rocky/woodland habitats), linking arthropod biomass to higher trophic levels and serving as prey for larger predators (raptors, snakes, larger varanids).

Top-down regulation of large arthropod populations (e.g., termites, orthopterans, beetles) Soil turnover/microhabitat modification via digging and burrow use (bioturbation) Energy/nutrient transfer from invertebrates to vertebrate predator guilds

Diet Details

Main Prey:
Termites Ants Beetles and beetle larvae Grasshoppers, crickets, katydids Cockroaches Spiders and scorpions Centipede Large arthropods Small lizards +3

Human Interaction

Domestication Status

Wild

The Red Ackie Monitor (Varanus acanthurus) is not domesticated; it stays wild though widely bred in captivity. People have long known and sometimes used it in northern and central Australia, studied it in the wild, and keep it in zoos and as pets abroad. Australia protects it and limits exports.

Danger Level

Moderate
  • Bites and deep scratches: sharp teeth and claws can cause lacerations requiring wound care, especially from adults or stressed animals.
  • Tail-whipping/defensive strikes: the spiny tail can cause painful welts or cuts at close range.
  • Zoonotic disease risk typical of reptiles (e.g., Salmonella): requires strict hygiene and safe handling practices.
  • Heat/UV hazards to keepers: improper enclosure setup can cause burns or electrical/fire hazards (human risk is indirect but common in reptile keeping).

As a Pet

Suitable as Pet

Legality: United States: usually legal, but some states/local rules ban varanids or need permits—check laws. Australia: strict state rules and export limits; most Red Ackie Monitors (Varanus acanthurus) in trade are captive-bred abroad. CITES may apply.

Care Level: Experienced

Purchase Cost: $300 - $1,500
Lifetime Cost: $4,000 - $15,000

Economic Value

Uses:
Pet trade (captive-bred herpetoculture) Zoo and educational display animals Research/field studies (varanid ecology, thermoregulation, behavior)
Products:
  • captive-bred live animals (pets/breeding stock)
  • education/outreach value (exhibits, programs using live animals)

Relationships

Related Species 7

Storri monitor Varanus storri Shared Genus
Kimberley rock monitor Varanus glauerti Shared Genus
Pygmy mulga monitor Varanus gilleni Shared Genus
Black-headed monitor Varanus tristis Shared Genus
Timor monitor Varanus timorensis Shared Genus
Pygmy monitor Varanus brevicauda Shared Genus
Sand goanna Varanus gouldii Shared Genus

Ecological Equivalents 4

Animals that fill a similar ecological role in their ecosystem

Sand goanna Varanus gouldii Overlaps broadly in arid and semi-arid Australian habitats. Both are diurnal, active-foraging predators that use burrows and termite mounds for refuge. The ecological similarity is primarily in foraging mode (wide-ranging, visually oriented predation) rather than body size—V. gouldii is much larger.
Black-headed monitor Varanus tristis Shares the small-monitor niche in northern and central Australia. It is diurnal, primarily eats insects and small vertebrates, uses crevices and burrows for shelter, and shifts activity seasonally in response to temperature and prey availability.
Central bearded dragon
Central bearded dragon Pogona vitticeps Similar arid-zone, diurnal, terrestrial lifestyle and use of burrows and shade for thermoregulation. While Pogona is more omnivorous, both occupy ground-level predator roles in spinifex and sandy habitats and display comparable basking and retreat behaviors to manage body temperature in hot environments.
Thorny devil
Thorny devil Moloch horridus Overlap in arid spinifex habitats. Both are diurnal, terrestrial reptiles that eat arthropods (thorny devil mainly ants) and face the same predators: raptors, snakes, and introduced mammals.

The red ackie prefers burrowing to climbing.

Red Ackie Monitor Facts

  • Master of disguise: The color and pattern of the red ackie’s spots correlate with their natural habitat to help them camouflage to prevent easy detection by predators.
  • Defense mode: Red ackie monitors in the wild mostly use their spiny tails as a means of self-defense against predators. When threatened, they wedge themselves in-between rock crevices and block the opening with their tails.
  • Red ackie monitors are one of the smaller species of monitor lizards and are often preyed upon by larger monitors.
  • Underground dwellers: Red ackie monitors prefer a hot, dry climate and burrow underground to keep their humidity and temperature under control.

Summary

Red ackie monitors are one of the smaller species of monitor lizards. Their name comes from the pronunciation of their specific name “acanthurus.” In addition to this, they have an beautiful pattern of red and reddish-orange spots which makes them attractive as pets. Red ackie monitors are highly curious and active lizards. They make great pets if you give them the proper housing space and diet.

Scientific Name

The scientific name of the red ackie monitor is Varanus acanthurus. The name “ackie” comes from the pronunciation of the Latin specific name “acanthurus.” They have red and reddish-orange spots on their body. Other common names for the red ackie monitor are red ridge-tail monitors, red spiny-tailed monitors, and red ackie dwarf monitors.

The red ackie monitor belongs to the Varanidae family with other carnivorous lizards such as the Asian water monitor, crocodile monitor, and black-throat monitor. The genus Varanus is the only genus of this family that contains living species.

Appearance

Ackie Monitor

Ackies are docile, curious, and intelligent lizards.

Red ackie monitors are generally medium-size, lengthy and slender lizards. They have short legs, tapered snouts, a snakelike tongue, and a long tail. Their tails are about 1.3 to 2.3 times longer than their body. Red ackies are also covered in scales which resemble spines, hence their nickname “spiny-tailed” monitor. The middle part of their body can contain anything from 70 to 115 scales. They typically have three pale stripes on their pointed head that streak down to their neck.

Red ackie are dark brown lizards with reddish-orange spots with dark dots inside them. These patterns morph into bands around the tail.

Red ackies are much smaller than most other monitor lizards. Because of this, they are “dwarf” monitors. They are usually about two feet long, with their tails making up about half of this length, but some red ackie monitors have been recorded to be as small as 17.3 inches and up to two and a half feet.

Behavior

Red ackies are curious and active lizards. Their size makes them popular as pets because they are easier to handle than bigger monitor lizards. They are perfect for owners who want to start small at lizard-keeping.

Ackies are some of the best monitor lizard pets as long as they are given the proper care and shelter they need. They are gentle, and can live in captivity for up to 15-20 years. They have a great temperament and do not typically get defensive unless mishandled, or afraid. When handling red ackie monitors, it is important to start small by rubbing the lizard first before eventually picking it up for short minutes daily. You can also be present in their enclosure for periods of time without touching them to allow them to get used to you.

Red ackie monitors are a burrowing species, and spend considerable amounts of time underground. They love to dig and burrow, so it is imperative that they be given enough space to do so. These monitors also prefer damp soil because it enables them to control their humidity and stay hydrated. Housing a red ackie can be expensive because of the space they need to be able to exercise.

If your pet red ackie tends to burrow right after you feed it, or tries to stay away from you, do not force an interaction. Keep going steady until you eventually win their trust and they become accustomed to you.

Red ackie monitors are diurnal, which means that they are active during the day and prefer to rest at night. They are also very active lizards, loving to climb and move around freely. This species cannot thrive in a small environment.

Red ackies are usually solitary animals and don’t mind being kept alone. They can get territorial, so if you are thinking of putting two inside one enclosure, you might want to think again.

Habitat and Population

Red ackie monitor lizards are terrestrial lizards native to the arid regions of northwest Australia, and parts of Queensland. They are adapted to the dry woodlands and scrublands of these areas, as well as some of the islands off of the northern coast of Australia. Wild red ackie monitors can be found in rocky terrain and outcrops.

Red ackie monitors prefer hot, dry weather with enough rocks and boulders. They dwell under these rocks and within their crevices where the temperature is cooler. Red ackies also burrow underground. These burrowing spaces are important for the red ackie monitor as they enable them to regulate their temperatures and humidity. The monitors rely greatly on the humidity from the damp soil in these burrows to keep them hydrated enough to withstand the dryness of their environments.

Red ackie monitors are common in the wild as well as in captivity. They are listed as Least Concern on the IUCN Red List of Threatened Species.

Reproduction and Lifespan

While it is usually a cinch to tell male and female animals apart in other species like cats and dogs, with monitor lizards, they are not so easily distinguishable. The most accurate way to differentiate a male lizard from a female is by a process called hemipenal transillumination. With this method, you hold a non-heating light source around the tail area of the lizard to determine its sex. Male red ackie monitors are a bit bigger than the females, and they have bulkier heads and spikier scales under their tails.

Red ackies in the wild start the mating process from December all the way to March. The male red ackie monitor initiates the process and lives with the female monitor for about five days. They mate intermittently during this time, after which the female searches out a decent spot to lay her eggs. Female red ackies typically lay eggs at the end of rodent or termite nests where the temperature and humidity is optimal. In captivity, the female monitor will scout the enclosure until she finds an area suitable enough to dig tunnels. She will return after about 20 days to lay her eggs. The female red ackie will need plenty of nourishment to successfully lay her weight in eggs.

Breeding takes place from the spring to the summer and the eggs hatch after three to five months of incubation. Females can lay up to 6 clutches annually, providing around 6-18 eggs per clutch.

The hatchlings come out at about six inches long. The male red ackies become sexually mature at 12 inches long, and the females at about 10-14 inches. Adult red ackie monitors reach lengths of two to two-and-a-half feet.

When cared for properly, red ackie monitors in captivity have a relatively long lifespan of 15 to 20 years.

Diet

Red ackie monitors are carnivorous and prey on invertebrates such as caterpillars, spiders, grasshoppers, snails, crickets, cockroaches, beetles, and cicadas. They also eat smaller lizards, such as geckos and skinks. Calcium powder supplements should be brushed onto the insects before feeding the monitor. This will help supplement their calcium intake and prevent bone disease.

Whole animal prey such as small rodents can also be given to the red ackie monitor on occasion, depending on the weight of the monitor. Red ackies, unlike larger monitor lizards, are small and active. If the red ackie is too thin or too fat, that would determine the frequency of its meals. When selecting each meal, pet monitor owners should consider that about 70% of the red ackie’s water source is derived from the food it eats.

Red ackies will eat cat or dog food but this should not be their staple food because processed or canned food do not contain all the necessary nutrients red ackies require daily.

Predators and Threats

Red ackie monitors in the wild face many predators. Unlike larger monitors, they are quite small so intimidation is not on their side. They are preyed upon by larger monitor lizards, eagles, snakes, and raptors.

Red ackie monitors in captivity don’t have to worry about predators, but they do face certain health issues. Pet monitors are prone to metabolic bone disease (MBD) which results from calcium deficiency. When the monitor doesn’t receive enough calcium, its bones become brittle and weak, causing immobilization and, eventually, death.

Another common health issue red ackies face in captivity is obesity. This comes as a result of excess feeding. Determine feeding by the activity level of the monitor. The red ackies can be fed intermittently throughout the week instead of daily. Fatty foods like eggs should be given as treats on occasion. It is important to keep a watchful eye on the weight of your pet red ackie monitor so that it does not get too fat.

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Sources

  1. Swell Reptiles / Accessed November 5, 2022
  2. Wikipedia / Accessed November 5, 2022
  3. National Aquarium / Accessed November 5, 2022
Rose Okeke

About the Author

Rose Okeke

Hi! I am a writer, actor, and filmmaker. Reading is my favorite hobby. Watching old movies and taking short naps are a close second and third. I have been writing since childhood, with a vast collection of handwritten books sealed away in a duffel bag somewhere in my room. I love fiction, especially fantasy and adventure. I recently won the James Currey Prize 2022, so now, naturally, I feel like I own words. When I was 11, I wanted to be a marine biologist because I love animals, particularly dogs, cats, and owls. I also enjoy potatoes and chocolate in all their glorious forms.
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Red Ackie Monitor FAQs (Frequently Asked Questions)

Red ackies are on the smaller side of monitor lizards so they do not pose any serious danger to a human being. However, when aggravated or threatened, they can bite or whip their tails at their assailant.