Ackie Monitor Temperatures & Heating

ackie monitor temperatures and heating

Like other reptiles, ackie monitors are cold-blooded, which means that ackie monitor temperature is dictated by the temperature of their environment, instead of being able to maintain their own body temperature like humans and other mammals can. If we get more specific, reptiles are actually poikilothermic, which means that they regulate their body temperature by behavioral means, such as basking or burrowing. This process is called thermoregulation.

As heliotherms, ackie monitors are dependent on sunlight to warm them to optimal temperature. Basking in sunlight has many benefits for reptiles. Aside from the UVB and visible light aspect, which we’ve already covered, the warmth in sunlight helps with:

  • stimulating circulation
  • facilitating digestion
  • regulating hormones
  • fighting off illness
  • healing injuries
  • incubating eggs
  • managing parasites

A reptile’s health and its husbandry are inseparably intertwined. When it comes to caring for monitor lizards, one of the most important things you can do for your pet’s health is making sure that it has the right temperatures in its environment.

When an ackie monitor’s temperatures are too low, it can lead to health problems such as excess weight gain, gout, gastrointestinal disease, and a weakened immune system. It can also lead to appetite loss, lower digestive efficiency, reduced thyroid activity, reduced growth, possible putrefaction of food within the gut, and gastrointestinal impaction (Mendyk et al., 2014, p.623).

However, even when it has appropriately high basking temperatures, if it can’t escape the heat when needed, the reptile is likely to die from heat stroke.

Your ackie monitor’s temperature gradient should look like this:

  • Basking surface temperature: 158-172°F / 70-78°C
  • Warm side air temperature: 84-100°F / 29-38°C
  • Cool side temperature: 75-82°F / 24-28°C

Surface and cool side temperature recommendations sourced from preferential data in “On the Thermal Husbandry of Monitor Lizards” by Robert W. Mendyk et al.

Air temperature recommendations sourced from local climate data.

Use a digital probe thermometer with the probe on the basking area to measure approximate air temperature there. An infrared temperature gun can be reliably used to measure basking surface temperature when pointed at that area from the manufacturer’s recommended distance. This measurement should be taken from the basking spot a couple of hours after the basking rock has warmed up.

I like using an Exo Terra or Zoo Med digital thermometer and Etekcity 774 temp gun for measuring temperatures.

Heating should be turned off at night.

How to Heat the Basking Area

As heliotherms, monitor lizards associate the presence of light with a potential basking location, so the basking area should be the brightest part of the enclosure. This is assisted by placing UVB and LED lighting near the heat lamp on the warm side, but you also need a heat source that produces both heat and visible light.

However, not just any old light-producing heat source will do. As it turns out, there are multiple different types of infrared (heat), and the differences between them matter.

Infrared A is the strongest wavelength of infrared, and penetrates deepest into animal tissue for efficient heating. IR-A is naturally produced by the sun, and artificially produced by metal halide and halogen bulbs. This wavelength also has healing properties.

Infrared B is the second-strongest wavelength of infrared, and also has deep penetration properties, but not quite as deep as IR-A. IR-B is naturally produced by the sun, and artificially produced by metal halide and halogen bulbs, as well as deep heat projectors.

Infrared C is the weakest wavelength of infrared, also known as radiant heat. It is unable to penetrate past the skin surface, making it inefficient as a basking heat source. IR-C is produced when IR-A and/or IR-B come in contact with a surface, so it is not produced in significant quantities by the sun. IR-C is artificially produced by deep heat projectors, ceramic heat emitters, radiant heat panels, heat mats, and heat tape.

For more information, read “Next Level Heating: Why Infrared Wavelengths Matter” by Roman Muryn and “Fire — The Sun: Its Use & Replication Within Reptile Keeping” by John Courteney-Smith.

The best way to provide high quality, short-wave infrared heating to your ackie monitor is with halogen flood bulbs. In order to create a large enough basking area to evenly heat your monitor’s entire body, you will need **at least 2 heat bulbs** placed next to each other.

BEST: Infrared Lamp Unit

  • Pros: superior Infrared-A output, long-lasting, very wide beam, very even heating, wide range of wattage options
  • Cons: expensive, deep red tint

Not to be confused with a red-tinted bulb that is being advertised as an “infrared” lamp when it is, in fact, just a red heat lamp, the Reptile Systems Infrared Heat Unit has the best Infrared-A output available on the current market. If you can afford it, it’s well worth the investment!

If you’re wondering which wattage to get, helpful charts estimating temperatures by distance are available here.

GOOD: Halogen flood heat bulbs

  • Pros: affordable, dimmable, even heat output, wide beam
  • Cons: may not get hot enough, reptile-branded bulbs are more expensive

If you need to buy reptile-branded halogen bulbs because you’re in a pinch (ex: you live in California), make sure that the bulb is white, not red or blue. Handle it with gloves on to help preserve the bulb’s lifespan by keeping your skin oils off of it.

Best halogen flood bulbs for reptiles: Arcadia Halogen Heat Lamp, Zoo Med ReptiTuff Waterproof Halogen Lamp

What wattage of bulb do you need?

Ultimately that depends on the distance between the basking spot and the heat lamp. That being said, since ackie monitors need such high basking temperatures, you are most likely to need a halogen bulb with very high wattage. More watts = more heat output.

When in doubt, select the bulb with the higher wattage and after two hours, use a plug-in lamp dimmer to reduce the output as needed. However, if you need to dim the bulb by half or more, that means you need a lower-wattage bulb.

NOTE: There is likely to be a 5°F drop in temperature after the first few days, and then heat output will gradually decrease until the bulb eventually burns out. For this reason, it’s important to check your basking temperature regularly!

What heat lamp fixture should you use?

You will need a dome lamp fixture with a ceramic socket to reduce fire hazard. It must also be rated for your heat bulbs’ wattage. For bulbs less than 160w, the Zoo Med Combo Deep Dome Dual Lamp Fixture works well.

If you are mounting your bulbs inside of the enclosure, you will need an appropriately rated ceramic socket, such as the Arcadia Pro Ceramic Lamp Holder & Bracket. If there is any chance of the lizard coming into contact with the bulb, then you will also need a heater guard to prevent burns, like the Arcadia Heat Lamp Cage.

For best results, plug your heat lamps into a surge protector to preserve the bulb’s lifespan.

Creating a Basking Area

Once you have your heat lamps, you can create your basking area. Like your UVB and daylight lamps, the heat lamps should be placed to the extreme right or left of the enclosure.

Your basking area will go directly underneath the heat lamps. It should be large enough to fit your ackie’s entire body, and tall enough to be the highest point in the enclosure. This helps create a diverse temperature gradient, which is very important when you are dealing with such high basking surface temperatures.

Be mindful of the distance between the basking surface and the UVB. Also make sure that your monitor can’t come into contact with the heat bulbs, as that will burn them. You can use a heater guard, but keep in mind that if you’re using non-reptile branded halogen bulbs, they may be too large to fit. This is one of the reasons why I prefer enclosures with mesh tops.

There are many ways you can create a basking platform for your ackie monitor, but the best method is called a Retes Stack.

Retes Stack model by

For the flat surfaces, you can use kiln-dried wood, flagstone, slate tile, or concrete pavers. Stone and concrete are best at absorbing and retaining heat, making them the best option for creating each layer of your Rete’s Stack (especially when you use dark-colored stone!). However, wood can also be used in a pinch.

For the spacers, it’s easiest to use wood, since you can cut each piece to size. Each spacer should be rectangular in shape, long enough to span two parallel sides of the stack, and roughly the same height as your ackie from belly to back.

For stability, the Rete’s Stack should be anchored to the bottom of your enclosure. If you do not anchor the stack and simply place it on top of the substrate, it is quite possible that your ackie will dig under the bottom layer and get crushed when the stack collapses. Each anchor piece should be firmly secured to the bottom layer of the stack to prevent them from getting accidentally displaced.

Anchored Retes Stack model by

How long should ackie monitors bask for?

Basking sessions should be brief, but take place multiple times throughout the day.

There’s a common misconception in the reptile hobby that a healthy reptile should be basking for the majority of the day. Think about this from a natural history standpoint: if a wild reptile had to spend most of its time basking, that would require it to potentially expose itself to predators for the majority of the day, and would also drastically reduce the amount of time that it has available to hunt for food. It’s like charging your phone: would you rather have a phone that charges quickly, or one that charges slowly? Chances are that you prefer a phone that charges quickly — and as it turns out, reptiles need to be able to “charge” quickly too.

Why do ackie monitors need a “cool zone?”

For a reptile, having places to cool down is just as important to healthy thermoregulation as having places to warm up. If the entire enclosure is maintained at or near basking temperature, then the reptile’s body temperature will rise above what is healthy, the body will start to shut down, and the reptile will die from heat stroke.

Aside from helping lower body temperature as needed, having a cool zone also gives your ackie monitor a place to rest. As ectotherms, cool temperatures slow a reptile’s metabolism, enabling them to conserve energy and reduce water loss through evaporation.

For ackie monitors in the wild (and in captivity, to a lesser degree), burrows play a vital role in providing a cool escape from the heat.

Seasonal Cycling for Ackie Monitors

Although ackie monitors don’t hibernate/brumate, their natural habitat does experience a regular period of reduced temperatures during winter. This natural cycle seems to play a role in hormonal regulation for ackie monitors, as an annual cooling period is recommended for successful breeding in this species (Horn & Visser, 2007).

Providing an annual cooling period is not required, and many ackie keepers choose to skip this without too much apparent detriment to non-breeding monitors. However, because the cooling period seems to have an effect on an ackie’s hormonal cycling, and hormone balance is important to long-term health in animals, ReptiFiles recommends providing an annual cooling period as best practice.

According to “A Case of Hermaphroditism in the Ridge Tailed Monitor (Varanus acanthurus)” by Danny Brown, one way to do this is by providing heat for the full day period during summer and gradually reducing heat to just 4 hours/day during winter.

Food should continue to be available during the cooling period, as records of wild ackies’ seasonal diets indicates that they seem to eat during all months of the year (King, 2008).


  • Basking surface temperature: 158-172°F / 70-78°C
  • Warm side air temperature: 84-100°F / 29-38°C
  • Cool side temperature: 75-82°F / 24-28°C
  • Use a cluster of at least two halogen flood bulbs for heat.
  • Build a Retes Stack for your ackie to use as a basking platform.
  • Use digital devices to track temperatures.
  • Heat lamps should be turned off at night.
  • It is best practice to reduce heat during winter.

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