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  • Writer's pictureHerpetological Society of Singapore

Monitor lizards — More than just F1 track crashers and sewer dwellers

Updated: Apr 18

Written by Drima Chakraborty, HSS Member

November 2023

(Photo by Law Ing Sind)

A humble monitor lizard got its 15 minutes of fame when the Formula One circus rolled into town in September 2023.

While the rest of the world may have caught a glimpse of “Godzilla” for the first time, we in Singapore tend to be already familiar with these animals.

But are we really?

Here are some misconceptions you may have about monitor lizards and what’s really up with these scaly creatures.

1. They’re Komodo dragons, right?

We have three species of monitor lizards in Singapore: the Asian water monitor (Varanus salvator), the clouded monitor (Varanus nebulosus) and the rare Dumeril’s monitor (Varanus dumerilii). 

Sadly, none are Komodo dragons (Varanus komodoensis), which live on Komodo and nearby islands in Indonesia.

While komodos are the largest lizards on the planet, growing up to 3m and weighing 70kg, our Asian water monitors are no slouches. They’re the runners-up, generally not exceeding 2m (though the longest specimen came in at 3.21m) and 50kg.

Clouded monitors and Dumeril’s monitors come up at a diminutive size of up to 1.5m.

(A clouded monitor. Photo by Law Ing Sind)

2. They’re dirty sewer dwellers?

Sometimes, we see Asian water monitors chilling in longkangs (drains) and assume they’re dirty animals. They also live in forests, parks and mangroves. With Singapore’s rapid urbanisation, they’re some of the creatures that have adapted to venture into urban areas.

People may also disparage them as they eat carrion (decaying flesh of dead animals), but this plays an important role in the ecosystem. As scavengers, this helps to recycle nutrients within the ecosystem and thus, keeping the environment clean and healthy. They hunt, too, and eat a variety of prey — from insects, fish, and other reptiles to even mammals. 

Clouded monitors and Dumeril’s monitors, on the other hand, live in forests and largely eat things they dig up from the soil, including insects, snails and other invertebrates.

(Dumeril’s monitors live inside dense forests and mangrove swamps and are quite elusive. Photo by Law Ing Sind)

But do the habits and habitats of Asian water monitors mean they can pass diseases onto us?

The answer is maybe. Many reptiles carry the bacteria Salmonella in their digestive tracts, and humans could get it through close contact with reptiles or their environments, including their droppings. 

But this is mostly a concern for people in very close proximity with reptiles  — like those keeping reptiles in captivity — and shouldn’t affect us in Singapore when we encounter wild monitor lizards occasionally.

On the other hand, they could leave us with a nasty infection if they bite us (but so can domestic cat bites!). It’s up for debate whether monitor lizards produce venom, but it’s the bacteria in their mouths that we have to worry about. 

All the more reason for us to admire them from afar.

(Adult Asian water monitor. Photo by Drima Chakraborty)

3. They are aggressive.

Monitor lizards, like most animals, aren’t inherently aggressive and don’t attack unless they feel threatened. 

So, the best course of action is not to get too close to them or corner them.

Don’t chase after them — they won’t enjoy playing catch with us, nor will we if they give us a nip in self-defence.

(Juvenile Asian water monitor. Photo by Law Ing Sind)

As both predators and scavengers (though some species are herbivorous elsewhere in the world), monitor lizards help maintain ecological balance. They prevent the spread of diseases by eating decaying organic matter and play a crucial role in breaking down dead animals and recycling their nutrients.

So we must learn to coexist and appreciate our reptilian neighbours!

If you want to keep them at bay from your home, NParks recommends you:

  • Practice proper food waste disposal,

  • Seal holes and gaps in property,

  • Prune trees and overhanging branches to restrict access,

  • Install wire mesh or acrylic panes at least 1m high, and

  • Keep your pets safely indoors.

You can also call the NParks 24-hour Animal Response Centre at 1800-476-1600 or ACRES 24-hour Wildlife Rescue Hotline at 9783 7782 if one does come knocking at your door and you need assistance.

Download the OWN monitor lizard advisory here:

OWN Advisory - Monitors
Download PDF • 1.33MB


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