Common Indian monitor
The Bengal monitor (Varanus bengalensis) is a large terrestrial monitor lizard. Young monitors, however, may be more arboreal, but adults mainly hunt on the ground. Although large Bengal monitors have few predators apart from humans who hunt them for meat, younger individuals are hunted by many predators.
Young Bengal monitors are more colorful than adults. Young have a series of dark crossbars on the neck, throat, and back. The belly is white, banded with dark crossbars, and is spotted with grey or yellow (particularly in the eastern part of the range). On the dorsal surface of young monitors, there are a series of yellow spots with dark transverse bars connecting them. As they mature, the ground color becomes light brown or grey, and dark spots give them a speckled appearance. Bengal monitors have external nostril openings (nares) that are slit-like and oriented near horizontally and positioned between the eye and the tip of the snout. The nares can be closed at will, especially to keep away debris or water. The scales of the skin are rougher in patches and on the sides, they have minute pits, especially well distributed in males. These scales with micropores have glandular structures in the underlying dermal tissue and produce a secretion that may be a pheromone-like substance. Like other monitors, Bengal monitors have a forked tongue similar to snakes. The function is mainly sensory and is not very involved in the transport of food down the throat. Bengal monitors have fat deposits in the tail and body that serve them in conditions when prey are not easily available. The lungs have spongy tissue, unlike the sacs of other saurians. This allows for a greater rate of gas exchange and allows a faster metabolic rate and higher activity levels. Like all monitors, they have subpleurodont teeth, meaning the teeth are fused to the inside of the jaw bones. While monitor lizards are venomous, there are no reports of the effects of venom in Bengal monitors other than a very controversial case report of fatal renal failure as a result of envenomation from this species.
Bengal monitors are among the most widely distributed of varanid lizards ranging from Iran to Java. They are found in river valleys in eastern Iran, Afghanistan, India, Nepal, Sri Lanka, Pakistan, Bangladesh, and Burma. The subspecies, Clouded monitor, occurs in southern Burma, Vietnam, Cambodia, Thailand, Malaysia, Sumatra, Java, and the Sunda Islands. Bengal monitors are found both in dry semiarid desert habitats to floodplains, scrubland, and moist forest. They are also often found in agricultural areas.
Bengal monitors are solitary and usually found on the ground but can climb well. The young are often seen on trees and may also climb trees to escape from predators. The larger ones prefer to escape on the ground. On the ground, Bengal monitors sometimes stand on their hind legs to get a better view or when males fight other males. They can also swim well and can stay submerged for at least 17 minutes. Bengal monitors usually shelter in burrows they dig or crevices in rocks and buildings or in tree hollows. They can also use trees and bushes or abandoned termite mounds for shelter. Bengal monitors, like other varanids, sleep at night and are diurnal, becoming active around 6 AM and bask in the morning sun. During winter, in the colder parts of their distribution range, they may take shelter and go through a period of reduced metabolic activity. They are not territorial and may change their range seasonally in response to food availability. Bengal monitors are usually shy and avoid humans. They have keen eyesight and can detect human movement nearly 250 meters (0.15 miles)away. When caught, they may bite but rarely do so.
Bengal monitors are carnivores and scavengers. Their typical diet consists of beetles, grubs, orthopterans, scorpions, snails, ants, and other invertebrates. They may also feed on frogs, fish, lizards, snakes, rodents, and ground birds. Bengal monitors are also scavengers. They sometimes feed on dead animals. In areas where livestock is common, they often visit dung, where they forage for beetles and other insects.
Bengal monitors are polygynandrous (promiscuous) meaning that both males and females have multiple partners. The main breeding season takes place from June to September. Males, however, begin to show combat behavior in April. Females dig a nest hole in the level ground or a vertical bank and lay the eggs inside, filling it up and using their snouts to compact the soil. The females often dig false nests nearby and shovel soil around the area. They sometimes make use of a termite mound to nest. A single clutch consists of about 20 eggs. The eggs hatch in 168-254 days and only about 40 to 80% of the eggs may hatch. The young are independent at birth and become reproductively mature at around 2.5-3 years of age.
The main threat to Bengal monitors is hunting. They are hunted for skin, meat, ad sometimes because of fear. The fat of Bengal monitors is also used in traditional medicine.
The IUCN Red List and other sources don’t provide the number of the Bengal monitor total population size. Currently, this species is classified as Least Concern (LC) on the IUCN Red List but its numbers today are decreasing.
Bengal monitors are the main predators of many small animals in the ecosystems they live in, thus controlling their populations. The young monitors are important prey species for local predators such as pythons, birds of prey, mongooses, feral dogs, and other Bengal monitors.
