Living Dragons: Weapons, Defences and the Water Monitor Lizard

Though this predator is the second-largest lizard in the world, and very well adapted to the tropical environment it lives in, it is not at the top of the food chain

By Gerry Martin

The sun rises early over the mangrove forests of the Sundarbans, and gently lights the misty water surface. About a hundred yards ahead of us, we see something swimming across the creek leaving a large wake in the water behind it. A strong and muscular swimmer, this beast tucks its limbs tightly along its body and propels itself forward using its slightly laterally compressed tail. It is an animal that is obviously built for life in watery habitats.

Water monitor lizards are absolutely at home in the brackish, tidal waters of mangrove creeks. Photo: Gerry Martin
Monitor lizards use their tongues to pick up scents in their environment. They can smell food from a great distance in the slow-moving waters of tidal creeks. Cover Photo: Gerry Martin

The water monitor lizard (Varanus salvator) is the second largest lizard in the world, outsized only by the massive Komodo dragon from Indonesia. The longest recorded water monitor lizard was from Kandy Lake in Sri Lanka. It measured 3.21 m! However, there are very few instances of these lizards even reaching 3 meters in length, though in India, they are rarely found longer than 2.5 metres, which in itself is gigantic!

Although these lizards are common in many parts of their range, India, unfortunately, has very few of them left, primarily because of hunting and habitat loss. Water monitors have historically been hunted for their skin and meat wherever they existed on the mainland and in the Andaman and Nicobar Islands. However, humans are not the only threats faced by these amazing lizards.

Water monitors begin their lives inside their eggs that take between five and nine months to hatch. Already there are plenty of possibilities for something to go wrong. Often laid inside termite mounds or other subterranean chambers, the eggs face many risks, from fungus and predation to flooding of the nest cavity. Anything can go wrong.

Growing up to 2.5 metres in length, these lizards can often be seen basking on exposed branches of mangrove trees. Photos: Gerry Martin

When the young do hatch, they dig their way out of the chamber and look for the nearest branches to climb to stay safe. For the first year or so, these young giants will spend a lot of time in trees, coming down to the ground only to hunt their prey of insects, fish, crustaceans, small rodents, and any small animal they can overcome and swallow.

Young monitors are adept climbers and will scuttle up trees to get away from danger. Photo: Gerry Martin

As they grow, they begin taking on larger prey, frequently eating snakes, raiding crocodile nests, feasting on carrion, and pretty much anything they can sink their teeth into. They have a keen sense of smell, using their forked tongues much like snakes do to find and follow scents.

As adults, fewer animals can pose a risk to them, but they are never on top of the food chain in most of their range. Especially in mangrove habitats, they share their range with some very large carnivores. Salt-water crocodiles could easily take down and eat even the largest water monitor lizard. Tigers, leopards, king cobras, and pythons can and do prey on these seemingly indestructible reptiles.

But water monitor lizards aren’t pushovers either. They are equipped with an array of weapons and defences to make all these predators work for their meals.

Sharp, serrated teeth allow the lizards to deal with prey that many other animals would leave alone. Photo: Gerry Martin

They have really strong, sharp claws that they use to hold down their prey or defend themselves, serrated teeth that slice through flesh, a tail built to ward of a persistent attacker, and an almost mythically strong muscular body that allows it to command respect. In addition to this arsenal, the water monitor lizard has a bony skin that forms an armour over the dorsal part of its body. This armour is literally formed by deposits of bone called osteoderms inside the skin. To top it all, they are also immune to the venoms of the species of snakes found around them — a handy adaptation in their tropical world where venomous snakes are incredibly common.

Most knives will go dull on their skin, yet, when male monitor lizards fight, they tear into their opponent’s skin with their claws. Standing on their hind legs, they grab hold of each other and try to wrestle the other to the ground. It is quite a sight to watch two massive males duel for the right to mate.

Females are significantly smaller than males. Mating usually takes place in the water and is seasonal, usually during the rainy season in India. After a few weeks, the female will head away from the tidal mangrove creeks to higher ground and find a termite hill, burrow, or even dig her own little chamber in the ground, where she will lay five to twenty eggs. She will then close up the chamber and leave. Her job is done and she will play no further role in her offspring’s lives. She must then go on and feed and rebuild herself for the next season.

In a scene that has been played out for millennia, a large male monitor lizard swims across a creek, climbs onto the muddy bank, and begins lumbering along with tongue flicking out repeatedly, looking for something. It could be food or a mate. Who’s to know? Hopefully this act will continue to persist through the trials it faces in the mangroves and other wetland habitats it inhabits around the world.

Gerry Martin

is the founder director of The Gerry Martin Project, and has been involved with herpetological research and conservation, documentary filmmaking, education and eco-tourism over the past decade.

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