Water Monitor




Range: Indo pacific Islands

Habitat: Dense Tropical Forests, to coastal plains.  Habitat varies widely by island.   This species is known to venture into salt water estuaries to hunt for mollusks and fish.

Natural Diet: Carnivore, very opportunistic feeders.  Will also eat carrion.

Diet at Rain Forest: Rodents, chicken.  Diet is supplemented with various vitamins. 

Size: 5-8 feet in length, may weigh as much as 80 pounds.

RainForest Facts: The second largest living lizard species on earth.  The Water Monitor is the second heaviest monitor on our planet.  The Crocodile monitor actually grows longer than both the Komodo Dragon as well as the Malayan, or Asian Water Monitor but does not attain the body weight of these lizards.  The water monitor closely resembles the Komodo Dragon. 

The Water Monitor's main hunting technique is to run after prey that it has spotted, rather than stalking and ambushing. Like snakes, they have a forked tongue that they stick in and out regularly to "smell" for potential prey. 

The name "monitor" probably originated from the superstitious belief that Nile monitors warned of the presence of crocodiles. Nile monitors eat crocodile eggs and were therefore often seen near crocodile nesting sites.
Water Monitors are rarely found far from water. Both fresh and saltwater. They are particularly common in mangroves, banks of large rivers. Also found in grasslands, forests, swamps, beaches and even cultivated land. From sea level up to 1,100m high. They are among the first large vertebrates to colonize new islands.




Water Monitor Lizards are highly mobile. They swim well (keeping their limbs to the side of the body, and propelling themselves through sinuous undulations of the flattened tail). They have even been seen swimming far out at sea. They can remain underwater for up to half an hour. They run fast for their size as they have powerful leg muscles. In fact, they are faster than most of us can run.

They also climb well, to search for food as well as to escape predators, using their strong curved claws. The young usually stay in trees for safety. If cornered up a tree, they will jump into the safety of a stream or river.

They usually hide in a burrow built in a river bank. The entrance starts on a downward slope but then increases forming a shallow pool of water. The average length of the burrow is about 9.5 m, the average depth is about 2m. In the burrow, the average temperature is around 26 degrees Celsius.


Water Monitor lizards breed relatively young compared to other species of monitor lizards.   Larger females produce a larger clutch than smaller, younger females.  Up to 40 eggs a year in 2 or more clutches are relatively common.   Mating of both captive and wild animals generally involves a lot of biting and scratching.  Females lay their eggs 4 to 6 weeks after breeding.  3 to 25 white, soft-shelled eggs are laid, with an average of 15 per clutch.  Eggs are laid in termite mounds (both active or abandoned mounds), along rotting logs or hollow stumps or in burrows. Eggs take 2.5-10 months or more to incubate.

Juveniles are more brightly colored with bright yellow markings on the body and yellow bands on the tail contrasting against a darker body. But they are more secretive and less commonly seen. Males grow faster than females, become longer and heavier. In ideal conditions, they reach maturity in 2 years at 1-1.3m for males and 0.5-1.2m for females. Water Monitors can live for up to 15 years.

Role in the habitat: As is often the case with large predators their roll in the environment is actually fairly complicated.  Large monitors such as the water monitor act as both scavengers and aggressive predators.  By scavenging (eating carrion) Water Monitors help keep the overall habitat free from potentially problem causing rotting animal flesh.  As aggressive predators they help keep rodent and other vermin populations under control.  They in turn provide food for larger carnivores such as crocodiles and birds of prey. Small young Water Monitors are particularly vulnerable even to large birds such as herons.


When attacked, Water Monitors try to intimidate predators by lashing out with their tails, inflating their throats, hissing loudly, turning sideways and compressing their bodies. When cornered, they will bite and claw. Unlike other lizards, they do not drop their tails in self defense.

Water Monitors are a source of protein and income to poor rural people. Sustainable harvesting is possible because even in places where they are hunted, they are still rather common.

Status and threats: Water Monitors are not considered endangered although they are commonly hunted for their meat and skin and have been exterminated over most of mainland India. Elsewhere, populations have declined sharply. Habitat destruction also affects them. Up to 1.5 million skins are legally exported each year mainly from Indonesia to Europe, Japan and the US to be made into fashion goods. One explanation why they remain plentiful despite this is because the skins of medium-sized Monitors are preferred. Those of larger Monitors are too thick and tough, thus possibly sparing large females who lay more eggs. Their meat is considered delicious and a bewildering array of potions are made from various parts of their bodies, ranging from cures for diabetes to aphrodisiacs and deadly poisons used in assassinations. The gall bladder is brewed for a medicinal tea to treat heart and liver problems. Skin ointments are made from the rendered fat. In Sri Lanka, the locals protect them because they eat the crabs that would otherwise undermine the banks of the rice fields.