Ackie Monitor (Varanus acanthurus) Care Sheet
Quick Facts
Common Names: Ackie Monitor / Spiny-tailed Monitor / Ridge-tailed Monitor
Scientific Name: Varanus acanthurus
Family: Varanidae
Native Range: Northern, western and central Australia
Adult Size: Commonly approximately 50–70 cm (20–28 in), with some individuals approaching 75 cm
Lifespan: Approximately 15–20+ years with appropriate care
Activity: Diurnal
Lifestyle: Terrestrial, saxicolous and strongly associated with burrows and rocky retreats
Diet: Predominantly insectivorous/carnivorous
Reproduction: Oviparous (egg-laying)
Temperament: Highly active, inquisitive and intelligent
Experience Level: Intermediate to advanced
Introduction
The Ackie Monitor (Varanus acanthurus) is one of the smaller members of the monitor-lizard family and one of the most popular monitors maintained in captivity.
Its relatively modest adult length can be misleading.
An Ackie is still an extremely active, intelligent monitor requiring considerably more environmental complexity than many similarly sized reptiles.
Successful husbandry requires:
- A large enclosure
- Very deep diggable substrate
- Intense basking heat
- Appropriate UVB
- Bright visible lighting
- Numerous secure retreats
- Climbing opportunities
- A varied prey-based diet
- Environmental enrichment
Ackies are often described as one of the more manageable monitor species, but they should not be treated as conventional small pet lizards.
Their intelligence, activity and behavioural requirements make high-quality enclosure design extremely important.
Natural Range
Ackie Monitors occur across large areas of:
- Northern Australia
- Western Australia
- Central Australia
- Some offshore islands
They inhabit some extremely hot and seasonally dry environments.
However, this does not mean they should be maintained in uniformly hot, completely dry captive conditions.
Natural Habitat
Ackies are associated particularly with:
- Rocky outcrops
- Boulder fields
- Spinifex grassland
- Scrub
- Seasonally dry woodland
- Rocky crevices
- Burrows
They frequently retreat into:
- Rock cracks
- Burrows
- Spaces beneath rocks
These retreats provide significantly cooler and more humid microclimates than exposed daytime surfaces.
This is one of the most important concepts in Ackie husbandry.
The captive enclosure should reproduce:
Very hot exposed basking areas + cooler, more humid retreats.
Red & Yellow Ackies
Captive Ackies are commonly sold as:
- Red Ackies
- Yellow Ackies
These names are useful descriptions of colour and appearance but should not automatically be treated as proof of genetically pure locality or subspecies.
Captive populations have been maintained for many generations and exact ancestry is not always documented.
Individuals can also vary considerably in:
- Colour
- Pattern
- Adult size
regardless of the commercial label attached to them.
Size
Adults commonly reach approximately:
50–70 cm (20–28 inches)
in total length.
Some individuals may approach approximately:
75 cm (30 inches).
A substantial proportion of the total length consists of the tail.
Males generally become:
- Larger
- More robust
- Broader-headed
than females.
Lifespan
With appropriate care, Ackie Monitors can live approximately:
15–20+ years.
This makes them a significant long-term commitment.
Enclosure Size
For a single adult, approximately:
150 × 75 × 75 cm
should be regarded as a practical minimum target.
An enclosure around:
180 × 90 × 90 cm
or larger provides substantially greater opportunity for:
- Exercise
- Digging
- Climbing
- Foraging
- Thermoregulation
- Environmental enrichment
Larger accommodation is strongly encouraged where practical.
Why Space Matters
Ackies are highly active monitors.
They naturally:
- Patrol
- Dig
- Climb
- Hunt
- Investigate
- Bask
- Retreat
An enclosure should therefore contain multiple usable environmental zones.
Simply providing enough room for the animal to turn around does not constitute adequate housing.
Housing Individually
For routine husbandry, Ackies are safest housed:
Individually.
Although pairs and groups have historically been maintained successfully in very large, carefully managed enclosures, cohabitation can result in:
- Competition for food
- Competition for basking positions
- Territorial stress
- Persistent breeding pressure
- Injury
The absence of obvious fighting does not prove that both animals are thriving.
Individual housing also makes it much easier to monitor:
- Feeding
- Weight
- Faeces
- Behaviour
- Reproductive condition
- Health
Animals should normally only be introduced deliberately for controlled breeding.
Substrate
Deep substrate is one of the most important components of Ackie husbandry.
Provide approximately:
30–45 cm (12–18 inches)
of diggable substrate across a substantial portion of the enclosure.
Deeper areas are beneficial where enclosure construction permits.
Suitable mixtures can include:
- Organic topsoil
- Washed play sand
- Clay-containing soil
- Appropriate naturalistic reptile substrate mixtures
The mixture should be capable of retaining burrow structure.
Burrowing
Ackies are powerful and enthusiastic diggers.
Burrowing allows them to regulate:
- Temperature
- Humidity
- Security
- Exposure
It also provides substantial physical and behavioural enrichment.
A thin layer of substrate prevents one of their most important natural behaviours.
Substrate Moisture
The substrate surface can remain relatively dry.
Deeper layers should retain some moisture.
The aim is to create:
Dry surface conditions + progressively more humid conditions below ground.
Deep substrate should be moist enough to:
- Hold a burrow
- Maintain humidity
- Prevent complete desiccation
without becoming:
- Saturated
- Muddy
- Waterlogged
Do Not Chase a Specific Underground Temperature
There is no need to maintain every part of the substrate at one exact temperature.
Older husbandry advice sometimes specifies that substrate at a particular depth must remain at a fixed temperature.
A better approach is to provide multiple gradients.
The animal should be able to choose between burrows that vary in:
- Temperature
- Depth
- Humidity
Behavioural choice is more valuable than attempting to engineer one identical underground environment throughout the enclosure.
Hides
Provide multiple secure retreats.
Suitable hides include:
- Cork tubes
- Rock-style hides
- Artificial burrows
- Retes-style stacks
- Secure stacked slate
- Buried tunnels
Provide retreats at different temperatures.
The monitor should not have to choose between:
Feeling secure
and
thermoregulating correctly.
Rock Structures
Ackies naturally use tight rocky spaces.
Secure rock-style structures can therefore provide excellent enrichment.
However, heavy objects must be:
Supported from the enclosure base.
Never place heavy rocks loosely on top of deep substrate.
The monitor may excavate beneath them, creating a collapse hazard.
Retes Stacks
A Retes-style stack consists of securely spaced horizontal layers that create several narrow basking and retreat levels.
These can provide Ackies with a choice of:
- Surface temperatures
- Heights
- Exposure
- Security
They can be extremely useful when properly constructed.
All components must be stable and capable of supporting the animal safely.
Climbing
Ackies are often described as terrestrial monitors, but they are capable and enthusiastic climbers.
Provide:
- Branches
- Cork
- Rock ledges
- Platforms
- Diagonal structures
Climbing opportunities increase usable enclosure space and provide exercise.
Basking Temperature
Ackie Monitors require access to a very hot basking surface.
A useful starting target is approximately:
50–60°C (122–140°F)
measured at the basking surface.
Some individuals may voluntarily use hotter surfaces when an appropriate gradient is available.
The crucial point is that the animal must always be able to leave the intense basking zone.
Surface Temperature vs Air Temperature
This distinction is essential.
The surface beneath the basking lamps may reach 50–60°C while surrounding air temperatures remain substantially cooler.
The entire enclosure should never be maintained at basking-surface temperatures.
Measure:
Basking surfaces: infrared thermometer
Air temperatures: digital probe thermometers
Broad Basking Area
A monitor should not have to balance beneath one tiny extremely hot bulb.
Use appropriately positioned halogen flood lamps to create a broad basking area.
Ideally, much of the animal’s body should be able to warm simultaneously.
A broad basking zone also reduces the risk of concentrating excessive heat on one small area of skin.
Ambient Temperatures
A useful daytime gradient is approximately:
Warm area: 30–35°C
Cool area: 24–28°C
Basking surface: approximately 50–60°C
The animal should have unrestricted access to the cooler end.
Night Temperature
Night temperatures can generally decrease to approximately:
20–24°C
for healthy animals.
All visible basking lamps should be switched off at night.
If supplementary nighttime heating is genuinely required because the room becomes excessively cold, use an appropriate non-light-emitting source.
Heating Safety
All heating equipment must be installed securely.
The animal must never be able to contact:
- Exposed bulbs
- Ceramic elements
- Hot fittings
- Dangerous electrical equipment
Ackies climb and dig extensively, so heating equipment that initially appears inaccessible may become reachable once enclosure furnishings change.
Appropriate thermostatic control should be used.
UVB
Ackies are strongly diurnal reptiles that naturally experience intense Australian sunlight.
Appropriate UVB should therefore form part of their captive husbandry.
A high-output linear T5 UVB system is normally appropriate.
However, UVB should not be selected solely according to a lamp percentage such as:
“10%” or “12%”.
Actual UV exposure depends upon:
- Lamp model
- Reflector
- Distance
- Mesh obstruction
- Installation
- Lamp age
UV Index
A useful target around the primary basking zone is approximately:
UVI 4–6
with a gradient toward:
- Lower exposure
- Partial shade
- Complete shade
Where possible, actual exposure should be checked using an appropriate UV Index meter.
The monitor must be able to regulate its own exposure.
UVB & Basking
The primary UVB zone should overlap the basking area.
This allows the monitor to receive:
- Heat
- UVB
- Bright visible light
simultaneously during normal basking behaviour.
This more closely recreates exposure to natural sunlight.
Visible Lighting
Ackies inhabit extremely bright environments.
Bright visible illumination should therefore be provided in addition to:
- Heat
- UVB
Full-spectrum LED lighting can help create a properly illuminated daytime environment.
Strong visible lighting encourages:
- Activity
- Exploration
- Natural circadian behaviour
A monitor enclosure should not remain dim except for one bright basking spot.
Photoperiod
Approximately:
10–12 hours of light per day
provides a useful general schedule.
Seasonal variation can also be provided.
All visible lighting should be switched off at night.
Seasonal Cycling
Ackies experience seasonal changes in their natural environment.
Some breeders provide seasonal variation in:
- Photoperiod
- Heating duration
- Feeding
- Environmental conditions
particularly when attempting reproduction.
A pronounced seasonal cooling period is not essential for routine pet maintenance, but carefully managed seasonal cycling may be useful within breeding programmes.
Any environmental change should occur gradually.
Humidity
Ackie humidity cannot be represented adequately by one number for the entire enclosure.
Surface conditions can be relatively dry.
Burrows should provide substantially more humid conditions.
Ambient humidity may commonly fall around:
30–50%
depending upon climate and enclosure design.
Burrows and humid retreats may reach approximately:
60–80% or higher.
The important requirement is:
A humidity gradient.
Humid Retreat
Provide access to a humid retreat.
Suitable material includes:
- Moist soil
- Damp sphagnum
- Moist substrate beneath a secure hide
The retreat should be:
Damp rather than saturated.
This gives the monitor control over its own hydration and shedding environment.
Ventilation
Appropriate humidity must be combined with good ventilation.
Avoid:
- Completely desiccated enclosures
- Permanently wet enclosures
- Stagnant humid air
The goal is a predominantly dry surface environment containing more humid underground microclimates.
Water
Fresh drinking water should always be available.
Provide a stable bowl large enough for the monitor to drink comfortably.
Some individuals may soak.
Water should be replaced regularly and immediately whenever contaminated.
Diet
Ackies are active carnivorous monitors whose captive diet should be heavily based upon appropriately sized invertebrate prey.
Suitable staples include:
- Crickets
- Locusts
- Dubia roaches
- Other appropriate roaches
- Black soldier fly larvae
- Silkworms
- Appropriate beetle larvae
- Other captive-produced feeder insects
Dietary variety is strongly encouraged.
Invertebrate-Based Feeding
Insects should make up the majority of the routine captive diet.
This encourages natural:
- Hunting
- Chasing
- Digging
- Foraging
and helps reduce the obesity problems associated with excessive calorie-dense vertebrate feeding.
Rodents & Whole Vertebrate Prey
Small whole vertebrate prey can be offered occasionally as part of dietary variety.
However:
Rodents should not form the staple diet.
Frequent feeding of mice or other calorie-dense vertebrate prey can contribute to:
- Obesity
- Fatty liver disease
- Reduced activity
An insect-heavy diet is more appropriate for routine maintenance.
Feeding Juveniles
Juveniles are growing rapidly and require more frequent nutrition.
Young Ackies can generally be offered appropriately sized prey:
Daily or every other day
depending upon:
- Age
- Growth
- Body condition
- Meal size
A wide variety of feeder species should be introduced early.
Feeding Adults
Healthy adults generally require less frequent feeding.
A useful starting schedule is approximately:
Every 3–5 days
with quantity adjusted according to:
- Body condition
- Activity
- Sex
- Season
- Reproductive condition
- Prey size
Do not feed purely according to appetite.
Foraging Enrichment
Feeding provides an excellent enrichment opportunity.
Food can occasionally be:
- Scattered
- Hidden
- Placed beneath leaf litter
- Offered at different enclosure locations
This encourages:
- Searching
- Tongue-flicking
- Digging
- Movement
- Hunting
Do not leave uneaten feeder insects in the enclosure where they may disturb the monitor.
Gut Loading
Feeder insects should be properly gut-loaded before use.
Suitable foods include:
- Quality commercial gut-loading diets
- Leafy greens
- Appropriate vegetables
Well-fed insects provide better nutrition than feeders maintained on poor diets.
Calcium & Vitamin Supplementation
Supplementation should account for:
- UVB exposure
- Feeder species
- Gut loading
- Age
- Growth
- Reproductive condition
- Supplement formulation
Plain calcium can be used appropriately with insect prey.
A suitable reptile multivitamin can be provided periodically according to manufacturer instructions.
Vitamin D3 supplementation should take actual UVB exposure into account.
Avoid indiscriminate heavy supplementation.
Body Condition
A healthy Ackie should appear:
- Athletic
- Muscular
- Alert
- Active
Monitor:
- Weight
- Tail base
- Abdomen
- Limb musculature
- Activity
An extremely rounded, heavy monitor is not necessarily a healthy monitor.
Intelligence & Enrichment
Monitor lizards are highly intelligent reptiles.
Ackies benefit greatly from environmental enrichment.
Suitable enrichment includes:
- Deep digging substrate
- Rock structures
- Climbing branches
- Tunnels
- Different textures
- Food-searching opportunities
- Novel safe scents
- Rearranged furnishings
- Multiple basking levels
Enrichment should encourage natural behaviour rather than simply making the enclosure visually attractive.
Handling
Ackies can become remarkably confident around their keepers.
However, trust should be developed gradually.
A frightened Ackie may:
- Hiss
- Hide
- Tail-whip
- Scratch
- Bite
- Attempt to escape
Forced handling can damage the keeper-animal relationship.
Building Trust
Use:
- Predictable routines
- Calm enclosure maintenance
- Food reinforcement
- Tong feeding
- Voluntary interaction
Allow the animal to approach rather than repeatedly grabbing it.
Over time many individuals learn to associate their keeper with positive experiences.
Tong Feeding
Tong feeding can be useful for:
- Building confidence
- Delivering specific foods
- Monitoring appetite
However, avoid encouraging uncontrolled feeding responses.
Never deliberately teach the animal to associate exposed fingers with food.
Bite & Scratch Risk
Ackies are much smaller than many monitors but can still inflict painful injuries.
Their:
- Teeth
- Claws
- Tail
should be treated with respect.
Any deep bite should be cleaned thoroughly.
Seek medical assessment for:
- Deep wounds
- Persistent bleeding
- Significant swelling
- Signs of infection
Shedding
Ackies shed their skin in sections.
Healthy shedding is supported by:
- Correct hydration
- Humid burrows
- Appropriate temperatures
- Good nutrition
Young animals shed frequently during rapid growth.
Retained Shed
Pay particular attention to retained skin around:
- Toes
- Tail tip
- Limbs
Persistent retained skin can restrict circulation.
Do not forcibly peel tightly attached skin away.
Instead review:
- Hydration
- Burrow humidity
- General husbandry
Persistent problems may require veterinary attention.
Quarantine
New animals should undergo appropriate quarantine before entering an established reptile collection.
During quarantine:
- House separately
- Use separate equipment where practical
- Monitor weight
- Monitor appetite
- Observe faeces
- Monitor hydration
- Check for external parasites
- Observe respiration
Veterinary parasite screening may be appropriate.
Common Health Problems
Obesity
Overfeeding is one of the most preventable captive problems.
Risk increases with:
- Frequent rodent feeding
- Oversized meals
- Insufficient exercise
- Small enclosures
Prevention requires appropriate portion control and environmental activity.
Metabolic Bone Disease
Problems involving:
- UVB
- Calcium
- Vitamin D3
- Nutrition
can contribute to metabolic bone disease.
Possible signs include:
- Weakness
- Tremors
- Soft jaw
- Limb deformity
- Fractures
- Difficulty climbing
Correct husbandry is essential for prevention.
Dehydration
An enclosure that is completely dry from top to bottom can contribute to chronic dehydration.
Possible signs include:
- Sunken eyes
- Poor skin condition
- Abnormal shedding
- Lethargy
Provide:
- Fresh water
- Deep moisture-retaining substrate
- Humid retreats
Thermal Burns
Ackies require extremely hot basking surfaces, making safe equipment installation particularly important.
The monitor must never be able to contact:
- Exposed bulbs
- Heating elements
- Dangerous fixtures
Burns require veterinary attention.
Nose Rubbing
Repeated rubbing against:
- Glass
- Doors
- Ventilation panels
can cause abrasions.
Possible causes include:
- Inadequate enclosure size
- Lack of environmental complexity
- Stress
- Attempts to escape
- Reproductive behaviour
Persistent nose rubbing should prompt an environmental review.
Respiratory Disease
Possible signs include:
- Mucus
- Wheezing
- Abnormal breathing
- Open-mouth breathing when not basking
- Lethargy
Respiratory symptoms require reptile-experienced veterinary assessment.
Parasites
Internal or external parasites can occur.
Possible signs include:
- Weight loss
- Abnormal faeces
- Poor body condition
- Reduced appetite
Veterinary testing should be considered where parasites are suspected.
Fatty Liver Disease
Chronic overfeeding and obesity can contribute to serious metabolic disease.
Prevention centres around:
- Appropriate diet
- Controlled portions
- Exercise
- Environmental enrichment
Maintaining an athletic body condition is considerably easier than treating advanced obesity.
Sexing
Sexing Ackies visually can be difficult, particularly when young.
Adult males generally become:
- Larger
- Broader-headed
- More robust
than females.
Some experienced breeders use:
- Tail-base characteristics
- Behaviour
- Reproductive history
- Imaging or specialist techniques
for more reliable sex determination.
Visual appearance alone should not always be considered definitive.
Breeding
Only healthy, mature animals in excellent body condition should be deliberately bred.
Breeding requires:
- Appropriate environmental conditions
- Excellent nutrition
- Deep nesting substrate
- Careful introductions
- Ability to separate animals
Females must have unrestricted access to suitable nesting substrate.
Breeding Condition
Females should have:
- Appropriate body reserves
- Strong calcium nutrition
- Correct UVB
- Excellent hydration
before breeding.
Egg production places substantial physiological demands on the female.
Courtship
Breeding behaviour can include:
- Increased activity
- Following
- Tongue-flicking
- Physical investigation
- Mating attempts
Introductions should be monitored.
Separate animals if persistent aggression or stress occurs.
Egg Laying
Ackies are:
Oviparous.
Females require deep, appropriately moist nesting substrate.
Clutches commonly contain approximately:
5–12 eggs
although clutch size varies according to:
- Female size
- Age
- Condition
Larger clutches can occur.
Nesting
A gravid female may:
- Become restless
- Dig extensively
- Investigate different areas
- Reduce food intake
Provide a deep nesting area containing substrate that:
- Holds tunnels
- Retains moisture
- Provides privacy
- Remains thermally stable
Inadequate nesting opportunities can result in serious reproductive complications.
Incubation
Ackie eggs can be incubated in an appropriate reptile incubation medium.
Temperatures around:
28–30°C
are commonly used.
Incubation generally lasts approximately:
90–120 days
although development time varies with:
- Temperature
- Moisture
- Individual development
Eggs should remain appropriately humid without sitting directly in standing water.
Hatchlings
Hatchlings require the same basic environmental principles as adults:
- Very warm basking surfaces
- Appropriate UVB
- Bright visible lighting
- Diggable substrate
- Humid retreats
- Fresh water
- Secure hides
Conditions should be scaled appropriately for their small size.
Hatchling Feeding
Young Ackies should receive a varied diet of appropriately sized invertebrates.
Suitable foods include:
- Small crickets
- Small roaches
- Small locusts
- Black soldier fly larvae
- Other suitable feeder insects
Young animals should be monitored carefully for:
- Growth
- Hydration
- Body condition
Cleaning
Remove:
- Faeces
- Dead insects
- Spoiled food
- Heavily contaminated substrate
as required.
Deep naturalistic substrate does not necessarily require complete replacement on a rigid schedule.
Instead:
- Spot-clean regularly
- Replace contaminated areas
- Monitor moisture
- Maintain burrow structure
Water bowls should be cleaned whenever contaminated.
Legal & Responsible Ownership
Monitor lizards may be subject to:
- International wildlife-trade controls
- Import/export requirements
- National animal-welfare legislation
- Local keeping requirements
Requirements vary by jurisdiction and can change.
Keepers should verify current regulations before:
- Acquiring
- Breeding
- Selling
- Importing
- Exporting
- Transporting
an Ackie Monitor.
Appropriate records demonstrating lawful origin should be retained where required.
Summary
The Ackie Monitor is one of the most manageable monitor species in terms of physical size, but it remains an intelligent, active and demanding reptile.
Successful husbandry centres around:
- A large enclosure
- Deep diggable substrate
- Secure burrows and rocky retreats
- A broad, extremely warm basking surface
- Much cooler retreat areas
- Appropriate UVB
- Bright visible lighting
- Humidity gradients rather than uniform dryness
- Fresh drinking water
- A varied invertebrate-heavy diet
- Controlled feeding
- Extensive environmental enrichment
- Individual housing
- Trust-based interaction
- Regular health monitoring
Three particularly important principles are:
Ackies need to dig.
Ackies need intense basking heat without an overheated enclosure.
Ackies need environmental complexity.
Their relatively small adult size should never be used as justification for small, simple accommodation.
When provided with sufficient space, deep substrate, intense lighting and opportunities to hunt, climb and excavate, Varanus acanthurus can display an extraordinary range of natural behaviour and is one of the most fascinating monitor lizards to maintain in captivity.
Important: This care sheet provides general husbandry guidance. Individual animals may require adjustments according to age, sex, health and reproductive condition. Veterinary concerns should be discussed with a suitably qualified reptile-experienced veterinary surgeon.