Dinosaurs roamed the earth for 160 million years until their sudden demise about 65.5 million years ago. We will never get them back. After dinosaurs, monitor lizards are the largest living lizards of this planet Earth that live in Africa, Asia, Australia and New Guinea.
To many people, monitor lizards are bizarre-looking creatures. Monitor lizards are considered menacing because of their seemingly expressionless faces combined with their claws, snake-like tongue and teeth. Most monitor lizards, in reality, are harmless to humans. However, there are certain monitor lizards that can kill, maim, make ill, or inflict at least mild levels of pain on their hapless human victims. Some monitor lizards are, in fact, venomous, and some are quite aggressive.
The diverse ecosystems of Bangladesh support three different monitor lizards species namely Bengal monitor lizard (Varanus bengalensis), yellow monitor (Varanus flavescens) and water monitor (Varanus salvator). In Bengali monitor lizards are popularly known as “guishap”.
Though monitor lizards are not snakes, most people in Bangladesh call monitor lizards a type of snake, perhaps because they dart their tongues out like snakes and when they swim they look a lot like snakes too. Though the monitor lizard species of Bangladesh are nonvenomous but most of the local people believethat they are venomous,
which is nothing but a lack of knowledge regarding these lizards.
Bengal monitor lizards are seen everywhere in Bangladesh, especially in forests, bushes, homestead gardens and agricultural lands. This large lizard is mainly terrestrial, and its length can range from about 61 to 175 cm from the tip of the snout to the end of the tail. Once upon a time, they were seen very often in our surrounding ecosystems but now they are rarely seen. The yellow monitor lizard, the smallest monitor of Bangladesh, inhabits diverse habitats but most commonly in marshy areas like haors and beels (marshes and wetlands). Yellow monitors reach a maximum length of approximately 100 cm. Females and males do not differ in size.
Water monitors, as their name suggests, are rarely found far from water and have no trouble swimming long distances. This ability has allowed them to colonise many remote islands. In Bangladesh they are most common in mangrove swamps of Sundarbans. With its length of up to 300cm, the water monitor is the second largest monitor lizard in the world. Only the Komodo Dragon (Varanus komodoensis), found in Indonesia, is bigger.
All monitor lizards are diurnal (active during the day) but mostly forage in the mornings and evenings. They have excellent eyesight and sense of smell - their forked tongue, which is protruded in the manner of snakes, helps them effectively find food. Large claws and a strong bite render it a formidable predator, with the adult monitor taking reptile and bird eggs, birds, arthropods, snails, frogs, skinks, insects, small turtles, snakes, fish, crabs, scorpions, and small mammals as prey. Monitor lizards are well known scavenger. If live food isn’t always available,
monitors will readily feed on carrion too. Young monitor lizards mostly feed on insects.
Most species of monitor lizards are harmless to humans with the main exception of the komodo dragon. Monitor lizards are only a danger to the insects and other small vertebrates and invertebrates they prey upon. A monitor lizard may bite humans but its bite is not toxic enough to really cause harm. The nasty and painful bite is normally caused by the strong jaws and bite of the lizard rather than the small amount of venom contained in it.
Monitor lizards are top predators and they play significant role in the food chain of a respective ecosystems where they inhabit. Monitor lizards are also considered beneficial to humans in many ways. They naturally control the populations of various harmful insects by eating them. They also protect our crops by hunting pests like rats. Monitors play an important role in an ecosystem not only as a key predator of rodents but also as scavengers.
Besides other scavengers monitor lizards play a major role in maintaining a healthy habitat. Dead animals, waste and rotting materials are a health hazard to living animals, as they can spread diseasebut scavengers like monitor lizards quickly break down the dead biomass, and everyone in the ecosystem benefits.
In Bangladesh, monitor lizards are hunted and killed for their skin. Together with illegal trade, rural people kill monitor lizards just based on some myths and misconceptions and children often play the key role in killing them. Due to anthropogenic factors and development activities their natural habitats are shrinking, and their populations are also decreasing in alarming rate.
To ensure the existence of these giant lizards in our surrounding ecosystems there is an urgent need to raise consciousness among the local people regarding these species. In these regards, community-based conservation education programme can be carried out to conserve these top predators. The involvement of local communities to achieve conservation goals is meant to foster public awareness and commitment. Therefore, the resulting integrated knowledge and understanding will provide a fundament for protection and conservation of monitor lizards.
* KM Mijanur Rahman is a PhD research scholar, Dept. of Bioecology, Hygiene and Public Health, Kazan (Volga Region) Federal University, Kazan, Russia