Water Monitor Lizard and its Many Defence Strategies
Photo StoryPublished : Mar 22, 2024Updated : Mar 26, 2024
When confronted with potential danger, the water monitor’s first instinct is to flee. Nonetheless, these semiaquatic lizards are equipped with a solid set of defence strategies, enabling them to thrive in water and on land
Text by: Tanvi Sawant
When confronted with potential danger, the water monitor’s first instinct is to flee. Nonetheless, these semiaquatic lizards are equipped with a solid set of defence strategies, enabling them to thrive in water and on land
In what is considered one of the very first descriptions of the Asian water monitor (Varanus salvator) in English literature, the sailor Robert Knox writes in his book first published in 1681: “He is not afraid of people, but will lie gaping and hissing at them in the way, and will scarce stir out of it. He will come and eat carrion with the dogs and jackals, and will not be scared away by them, but if they come near to bark or snap at him, with his tail, which is long like a whip, he will so slash them, that they will run away and howl.” Robert Knox, who worked for the British East India Company, recorded his observations and experiences during the 19 years he spent in Ceylon (now Sri Lanka) in An Historical Relation of the Island Ceylon (first published in 1681).
With a formidable demeanour and commanding gait, the Asian water monitor makes a fitting impression as one of the largest lizards in the world. A carnivore that is not too picky about its food, this monitor lizard is also an opportunistic predator. In India, the water monitor lizard is one of four monitor lizard species. It is found along the eastern coast, including the mangrove swamps of the mighty Sundarbans in West Bengal, Bhitarkanika in Odisha, the Andaman and Nicobar Islands and some parts of Northeast India. Native to South and Southeast Asia, it is widely distributed across its geographical range from eastern India to Bangladesh, Sri Lanka to the Philippines and Indonesia.
After the Komodo dragon, the water monitor is the second-largest lizard in the world and can grow up to three metres in length. Despite its massive size, which makes it look seemingly indestructible, it is not the apex predator in its preferred habitats. However, it has a solid set of defences to keep most predators at bay and adaptations to thrive in a variety of habitats.
Water monitors are semiaquatic varanids that thrive in places where waterbodies are nearby, including beaches, mangrove swamps, lakes, streams, and rivers. The Sundarbans mangrove forests make up a major part of the water monitor’s range in India. This rich mangrove ecosystem also harbours the water monitor lizard’s few predators: the Bengal tiger, the saltwater crocodile, and the king cobra. But these lizards are built to navigate the ever-changing landscape of the Sundarbans and have numerous ways of defending themselves. Photo: Dhritiman Mukherjee
When in danger, these primarily solitary creatures’ first line of defence is to try and get away. But when they have no choice but to fight against predators like snakes or even rival monitor lizards, their sharp claws, strong jaws, serrated teeth, and long, whip-like tails come in handy. Like in Knox’s description, water monitors use their tails as weapons. When they feel threatened, tired, or injured, (2) they may puff themselves up to look large and intimidating and hiss at stalkers. Photos: Akshay Manwani (1), Dhritiman Mukherjee (2)
Another morphological feature that helps these lizards defend themselves is their skin. Their thick skin is made of “osteoderms”, which are bony deposits that make their exterior almost impenetrable. Additionally, these lizards are immune to the venom of several venomous snakes that live in their vicinity and may prey on them. Photo: Dhritiman Mukherjee
Being able to swim is itself an advantage to these lizards. Their laterally compressed tail is one of the most distinct features in their arsenal when it comes to defence. The tail has a raised fin that allows them to move through the water effortlessly, contributing to making them excellent swimmers. Additionally, these mighty varanids can stay submerged underwater for extended periods of up to 30 minutes. While these adaptations are mainly useful when hunting in water, they also rely on them to try and escape predators. The water monitor’s ability to navigate the waters makes it a challenging prey. For instance, while the Bengal tiger is an excellent swimmer, it cannot stay underwater for as long. Photo: Dhritiman Mukherjee
As already established, water monitors know that running away is their best defence. With their powerful legs and sharp claws offering a strong grip, these massive lizards can effortlessly climb trees. Occasionally, they scamper up to the safety of a tree branch to escape potential predators. If the threat persists, or if a predator decides to pursue the monitor up the tree, they are also known to jump off trees into a stream to escape. Young water monitors are especially agile climbers. They spend most of their early life in the trees, safe and away from danger, occasionally foraging for small creatures like insects, crustaceans, mudskippers, and other fish. Photos: Akshay Manwani
(1) Water monitors climb trees not just to run away from predators (2) but also to rest. Their grey-brown colouration blends seamlessly with the barks of trees and in the muddy swamps of the Sundarbans. Unless you look very carefully, it is almost impossible to (3) spot the monitor among the ariel roots in this image. When camouflaged, the chances of being located by a predator are minimal until the monitor lizard moves. Photos: Akshay Manwani
The saltwater crocodile is a formidable predator that poses a significant threat to the Asian water monitor. In India, it is found along the east coast from the Sundarbans to Odisha’s Bhitarkanika and on the Andaman and Nicobar Islands. It is the planet’s largest living reptile, and the water monitor does not stand much of a chance in front of this apex predator. Water monitor lizards may raid crocodile nests to feast on their eggs. But when it comes to an adult saltwater crocodile, the monitor lizard is defenceless. Salties can grow up to five metres in length, almost double that of even the largest water monitor. Photo: Dhritiman Mukherjee
Although Asian water monitors are listed under the category of “Least Concern” on the IUCN Red List, their populations have been steadily declining in India. There are no official records of their population numbers, but they have historically been hunted for their skin and meat. Further, habitat fragmentation and loss pose significant threats to them.
The water monitor is highly adaptable and is known to inhabit agricultural areas and even cities in some parts of its range. However, the giant lizards are mostly misunderstood, feared, and extensively hunted. Despite their arsenal of defence strategies, the water monitor is helpless when faced with these threats from humans. Photo: Akshay Manwani
is a liberal arts graduate who is constantly seeking experiences that combine her multiple interests in art, cinema and the natural world. As a resident of Mumbai, she has a constant longing to spend time and find inspiration in nature!
