Common Water Monitor

Common water monitors are extremely opportunistic carnivores. They will eat anything they can catch and swallow. This includes birds, eggs, small mammals, fish, lizards, frogs, snakes, juvenile crocodiles, and tortoises. The primary hunting technique is characterized by 'open pursuit' hunting during the day, rather than stalking and ambushing. Monitors usually swallow prey whole.

At the Zoo, monitors receive a variety of meat options, including rats and fish.

Extremely widespread throughout southern and Southeast Asia; including China, India, Indonesia, Malaysia, Thailand, Vietnam, and Singapore.

Water monitors inhabit a wide variety of natural habitats across their native range. The habitats considered most important to this species are mangrove swamps, wetlands, rivers, and streams in tropical or subtropical areas.

The only natural predators of common water monitors are crocodiles and large snakes.

Although legal to hunt, overhunting beyond set quotas is a threat to water monitor populations in some areas. They are hunted for skin for the leather trade, meat, and fat used for traditional medicine. This species is common in the pet trade, with many individuals being wild caught juveniles or harvested eggs. Destruction of habitats for palm oil plantations, farming, and timber may have caused populations to decline in specific areas.

Dark in color with brown markings, individuals have a black band edged with yellow that extends back from each eye. Because of their color, they can blend in with their surroundings, so they are not seen by their prey. The neck of this monitor is very long with an elongated snout, allowing it to lunge out at prey. The nostrils are close to the end of the nose. They have a greatly enhanced sense of smell which they get through a special organ called the Jacobson's organ. This organ is also found in snakes, and like a snake, the water monitor will move its tongue in and out smelling the surroundings. Their jaws are extremely strong for their small head. Once bitten by one, it is a struggle to get them to release. Their body is made up of mostly muscle, and their tail is very strong and an effective weapon against predators. The tail is compressed from side to side, allowing for the tail to be used as a paddle while swimming. The scales on the top of the head are relatively large, while those on the back are smaller in size and are keeled. ("Keeled" scales refer to reptile scales that, rather than being smooth, have a ridge down the center that may or may not extend to the tip of the scale.) Water monitors are equipped with powerful limbs and sharp claws, which are good for digging and climbing.

Breeding season begins in April and lasts until October. Larger females produce a larger clutch size than smaller individuals. The eggs are usually deposited along rotting logs or stumps.

Water monitors mainly communicate visually through postures and other visual signs. They hold their heads up with their long necks, which shows the other animals and humans that it is alert and will attack if provoked or necessary. Their form of intimidation is lashing out with their tails, inflating their throats to make them seem bigger, hissing loudly, and tensing their bodies to give a fuller built effect.

The water monitor is a water-dependent species and has been known to cross large stretches of water, explaining its wide distribution. Though also found on flat land, a typical burrow is in a riverbank. The entrance starts on a downward slope, but then increases forming a shallow pool of water. When the monitor becomes the prey, usually by large snakes, it will climb trees with its powerful legs. Once in the tree, it may escape the threat, but if the danger is still present the water monitor will jump from the branch into the safety of a stream or river.