Lace Monitor Facts

Lace Monitor Profile

The Cretaceous period was home to many of the most famous dinosaur species, but there were plenty of epic non-dinosaur reptiles around at the time, too.

In the oceans, the formidable mosasaurs tormented anything wet, growing up to a possible 17 metres in length. 

And there’s strong evidence to suggest that a close relative of the mosasaurs still functions as a powerful predator, this time mostly on land, and in the form of the monitor lizards.

While they’re primarily terrestrial, monitors can still swim incredibly well, and actively pursue their prey in niches more commonly filled by warmer-blooded mammals. 

Unlike mosasaurs, they can also climb. The lace monitor, or tree goanna, is an all-terrain predator from Australia with numerous other improvements over its cretaceous ancestry, too. 

Lace Monitor Facts Overview

A lace monitor sounds like a terribly boring or very exciting job, depending on who’s wearing it, but it is in fact a relative of the snakes and mosasaurs of the past. It’s possibly more closely related to serpents than it is to other lizards, which would explain a few cool things about it. 

These are the world’s biggest lizards, and they can pack a serious punch. They eat almost anything made of meat and are happy, even if it’s not fresh.

Like snakes, they have venom and forked tongues, but like mammals, they chase you until you collapse in the foetal position, crying. And then they eat you.

Interesting Lace Monitor Facts

1. They’re Varanids

Of all the ongoing, traditional taxonomic debates, this one is probably the least painfully tedious. 

Monitor lizards sit in the Varanidae family; a group of lizards within the order Squamata, which contains both lizards and snakes.

That much is more or less established, but there have been over 200 years of argument between scientists about the relationships within this clade, with the two main opposing ideas being that monitors are either more closely related to snakes or extinct mosasaurs. 

Some say that mosasaurs represent a basal group to both snakes and monitors, but regardless, monitors appear to be a very distinct group of lizards with more similarities to extant snakes than other lizard species (if you ignore the four external legs).

It’s a fascinating proposal, either way, and the idea that mosasaurs still kind of exist in the form of terrestrial variants is very cool.

Animals like the Komodo dragon and the recently extinct Megalania provide a glimpse into how monstrous these lizards could get on land, and certainly have a Cretaceous appeal about them. 

On the other hand, they have very distinct serpentine features, too. As of 2025, there is no consensus. ¹

2. They’re big

There are old reports of lace monitors reaching 2.4m in length, but even if this was true, it isn’t any more. Still, these are the second-largest lizard in Australia, after the Perentie, which itself is the second-largest lizard on the planet. 

The infamous Komodo dragon is the largest, and there was even a monitor lizard in Australia that was twice the length of a car. But that one was too scary so we made it extinct about 40,000 years ago. 

So, of what’s left, the lace monitor is pretty large. And it’s nimble, too. ²

3. They’re fast

Monitors are unlike most lizards and even most other extant reptiles in that they chase down their prey. They have a higher metabolism than most reptiles, and this is what allows them to hunt in a manner more commonly associated with mammals than lizards. 

For example, as explosively fast as a crocodile is, it has neither the stamina nor the wherewithal to engage in a chase. It simply bursts out and hopes for the best (that’s why there’s no need to run in a zig-zag to get away from one – just running is enough). 

There’s no record of how fast the lace monitor is, but the much larger perentie can run at up to 40 km/h, which makes it the fastest lizard known.

The lace monitor, its arboreal cousin, won’t be as fast as this, but it’s safe to say this lizard gives its prey a run for its money. That is, if it’s not already dead. 

4. They’re excellent climbers

Most monitor species are competent in a variety of habitats – it’s what makes them so special. But while species like the Nile monitor spend more time in the water, and the perentie is a terrestrial specialist, the lace monitors are suited more to branchy habitats. 

They spend a lot more time in the trees as juveniles, and as they become more intimidating, come down to the ground more often as adults, but are always competent at scouring the trees, looking for prey. 

They have massive, hooked claws that are incredibly strong and excellent for climbing. And if they can’t find anything to kill, they’ll happily eat what’s already dead. 

5. They eat carrion

In fact, this species eats more carrion than live food, and will scavenge kills off other animals. They’ll also eat insects and other invertebrates, as well as mammals, reptiles, birds and their eggs; the latter two being quite easy to steal from nests up in the canopy. 

As accomplished scavengers, they do well around some of the things we throw away and can be found tearing into rubbish bags with food waste inside, or just setting up shop around tips, where they can be found in densities of thirty-five times higher than the surrounding area. 

They are not fussy eaters, and this can get them into trouble. Plastic ingestion can cause blockages, and one was found with six golf balls in it, alongside the three eggs it was there the steal in the first place. ³

6. They have forked tongues

Snakes can’t tear food into pieces, which makes their ability to eat carrion limited, but one stark similarity they have with lace monitors is their smell organ. 

This very snakey feature in monitors is their oral approach to sniffing. Like snakes, they have a forked tongue for directional olfactory exploration of their world. 

The fork allows the brain to tell which side the smell is coming from, which is also why animals have two nostrils, two ears, and so on. 

Interestingly, the unrelated Tegu family is filled with very monitor-like lizards and they, too have forked tongues. But this isn’t common in lizards. 

Perhaps an even more snake-like adaptation comes from what’s behind the tongue. ⁴

7. They’re venomous

For a long time, bites from Komodo dragons have been known to cause all kinds of bleeding and infection.

These are nasty mouths with a lot of bacteria and a lot of tissue-shredding teeth. The debate has raged back and forth about whether they could be considered venomous or just very, very grotty, but recently a consensus has begun to form. 

Not only are Komodos venomous, all varanid lizards are. Bites from a lace monitor will inject anticoagulant agents, among other things, and this is an evolved trait used specifically for predation. 

8. They’re smart

Monitors are well known for their intelligence, and this appears to have saved the lace monitor, at least when it comes to the invasion of the toad armies of Australia. 

Ever since Bart Simpson brought a cane toad to the country, these amphibians have spread all over the place, poisoning the local animals that don’t know they’re lethally toxic. 

But while the idiot marsupials are falling for the same tricks over and over again, the lace monitor populations seem to have learned not to eat them. 

This warm (ish) blooded generalist predator has enough blood in its brain to avoid one of the worst ecological disasters in the country’s history, and as of yet, it’s listed as of Least Concern by the IUCN.

Lace Monitor Fact-File Summary

Scientific Classification

1. “Mosasaurs”, Black Hills Institute.
2. Auckland Zoo (2017), “Zoo Tales – Large and beautiful lace monitors”, YouTube.
3. Jennifer Huxley (2019), “Goanna narrowly avoids surgery after swallowing six golf balls in chicken coop raid”, ABC News.
4. Auckland Zoo (2024), “Keeper Seth feeds the lace monitors!”, YouTube.