Monitor Lizards

What are they?

The most common monitor lizard among the three found in Singapore is the Malayan water monitor (Varanus salvator) that can grow up to 3m long. The other two species, the clouded monitor lizard (Varanus nebulous), and the rarest Dumeril’s monitor (Varanus dumerilii) can grow to a length of 1 to 1.5m. Monitor lizards are mostly carnivorous; some also scavenge on carrion. It can be found in forests, mangrove swamps, and even man-made canals!

  
Malayan Water Monitor Lizard (left) and Clouded Monitor Lizard (right).

Dumeril's Monitor Lizard.

Important Ecological Roles

Control of prey population
Monitor lizards feed on a huge variety of food types (eg. insects, crabs, snakes, fish); they control the population of their prey, and in turn are a source of food to larger predators (eg. crocodiles).

Keep habitat clean
They also play an important role as scavengers in biomass decomposition and recycling.

Common Concerns

The monitor’s saliva contains over 50 bacteria that infect and kill their prey slowly. Is this true?
The carrion meat that get stuck in the monitor’s teeth are teeming with bacteria that can cause infections in the bite wound. However, the main cause of death of preys is the venom secreted by the monitor.

Are monitor lizards venomous?
Contrary to previous beliefs, most lizards do possess glands that secrete venom. While the monitor uses its venom to kill its small preys (symptoms include rapid swelling, drop in blood pressure, and blood clot inhibition), it has a relatively mild effect on humans.

Are they dangerous?
They are naturally shy and would rather stay away from humans. Like most wild animals, they do not attack unless provoked. As long as you keep your distance and leave them alone, you will be fine.

Conservation
In Singapore, it is illegal under the Wildlife Act to remove wild animals, including monitor lizards, from the wild. Those found in nature reserves and other areas managed by NParks are also protected by the Parks and Trees Act 2005.

Poaching of monitor lizards exists in Singapore. However, they are often not brought to the attention of local authorities.

How can I help?

 

What to do when I encounter a monitor lizard?