The Bengal monitor is a large monitor lizard widely distributed over the Indian Subcontinent, as well as parts of Southeast Asia and West Asia. Males are generally larger than females. Young monitor lizards are more colorful than adults. Young have a series of dark crossbars on the neck, throat, and back. Their belly is white, banded with dark crossbars and are 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 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 the 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 m 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 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.