Are Monitor Lizards Dangerous?

Monitor Lizard in the Borneo island
© elena_photo_soul/

Written by Emilio Brown

Updated: November 7, 2023

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Quick Answers:

  • Yes, monitor lizards are dangerous in certain circumstances.
  • Monitor lizards will not typically attack humans unless provoked or feeling threatened.
  • Larger species have a powerful, venomous bite, but the venom is not lethal to humans in general. 

Being so large, you might have wondered: Are monitor lizards dangerous to humans? Monitor lizards belong to the genus of Varanus and are some of the largest lizards in the world. The majority of these lizards follow a carnivorous diet and feed off the local wildlife in their range.

In Asia, Africa, and parts of the Oceania region monitor lizards are found in various habitats. Most are terrestrial, but some species can be semi-aquatic or arboreal. In some areas within the U.So, you may find an invasive monitor lizard in the wild. Inexperienced reptile owners often find it difficult to keep these large lizards. As a result, pet monitors are commonly released into the wild.

Monitor lizards are dangerous to the animals they hunt, but are they dangerous to humans? Let’s find out how dangerous these giant reptiles are. 

Are Monitor Lizards Dangerous 

Nile monitor

Monitor lizards are usually dangerous when provoked but their bite is not fatal to humans.


Most times, monitor Lizards, will not attack unless they are provoked. Their long claws, sharp teeth, and powerful bodies make them more dangerous than other lizards. But it is rare for them to be aggressive towards humans.

But first, a warning: If you see a wild monitor you should not chase, or threaten them. They may get defensive when attacked. There are around 80 species of monitor lizards, and some are more dangerous than others. There are speculations, however, that these animals can attack humans when they are hungry. A case of a man attacked and killed by his pet monitor lizards was reported in 2018.

Larger species have a powerful bite, and can even hurt you with a strong tail whip. On the other hand, smaller monitors are not as dangerous, but can still deliver a painful bite.  Monitors are venomous, but their venom is not strong enough to kill humans, only small animals.  

Monitor Lizards Bite 

A monitor lizard’s bite is one of its most dangerous traits and it can cause severe pain. This species is venomous and its bite can kill its prey.  

However, the monitor lizard’s venom is not deadly to humans. It is deadly to smaller animals; possibly a small pet like a dog. Usually, humans will only have mild symptoms after being bitten. Here are some of the symptoms of a monitor lizard bite:

  • Pain
  • Swelling
  • bleeding
  • Headache  
  • Sweating 

People who experience severe symptoms after being bitten should get medical treatment as soon as possible. Unless you are allergic, the venom of monitor lizards isn’t fatal. But a bite can become infected with bacteria. Therefore, it’s important to treat bites from this animal immediately.

Additionally, bites by large species can cause severe damage. Since these animals are carnivores, their teeth are sharp and designed for ripping through meat. Thus, a larger lizard’s bite will cause more bleeding and can possibly tear through flesh and arteries.

Largest Monitor Lizards Species   

Dumbest Animals in the World: Komodo Dragon

Komodo dragons can grow to be three meters in length. Even though they are so big, Komodo dragons can be very fast when they are hunting prey.

©Yudi S/

Some species of monitors are more dangerous than others. Not every monitor lizard is giant, but some are capable of competing with the largest lizards in the world in size. Here are 10 of the largest monitor lizards species:

  1. Komodo Dragon (Varanus komodoensis)
  2. Asian Water Monitor (Varanus Salvator)
  3. Crocodile Monitor (Varanus salvadorii)
  4. Nile Monitor (Varanus niloticus)
  5. Perentie (Varanus giganteus)
  6. Black-Throated Monitor (Varanus albigularis microsticus)
  7. Lace Monitor (Varanus varius)
  8. Northern Sierra Madre forest monitor (Varanus bitawa)
  9. Gray’s Monitor (Varanus olivaceus)
  10. Bengal Monitor (Varanus bengalensis) 

Larger monitor lizards will have a more powerful bite. Even large monitors are not dangerous if you do not provoke them. Some large species like the Asian water monitor and black-throated monitor can make a unique pet for the right reptile owner. 

Most Dangerous Monitor Lizards  

Two Komodo Dragons (Varanus Komodoensis) do battle

©Sergey Uryadnikov/

The Komodo Dragon is the largest lizard in the world, and also one of the most dangerous monitor lizards. Adult Komodo Dragons weigh between 150 to 200 pounds. Record species have been reported getting as large as 300 pounds and growing 10 feet long. In the wild, these lizards are apex predators capable of taking out animals like deer, and boar. Attacks on humans are rare but deaths from this lizard have occurred.

 Komodo dragons are feared for their size, but the crocodile monitor has one of the worst bites of all monitor species. This species is able to grow larger than 8 feet and are known for their dangerous bite. Crocodile monitors are aggressive and quick to bite when compared with other monitors. Its bite is similar to that of a crocodile, which gives the crocodile monitor its name. They are arboreal and use the strong grip of their mouth to hold onto prey while climbing trees. Their teeth are sharp and are like knives in their mouth. 

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About the Author

Spiders, snakes, and lizards are my favorite types of animals, and I enjoy keeping some species as pets. I love learning about the various wonders nature has to offer and have been a writer for 5 years. In my spare time, you can find me getting out into nature.

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