Bengal monitor
Encyclopedia
The Bengal monitor or common Indian monitor, is a monitor lizard
found widely distributed over South Asia
. This large lizard is mainly terrestrial
, and grows to about 175 cm from the tip of the snout to the end of the tail. Young monitors may be more arboreal, but adults mainly hunt on the ground, preying mainly on arthropods, but also taking small terrestrial vertebrate
s, ground bird
s, egg
s and fish
. Although large monitors have few predators apart from humans who hunt them for meat, younger individuals are hunted by many predators.
Young monitor lizards are more colourful than adults. Young have a series of dark crossbars on the neck, throat and back. The 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 colour becomes light brown or grey, and dark spots give them a speckled appearance. Hatchlings of nebulosus tend to have a series of backward-pointing, V-shaped bands on their necks.
Bengal monitors have external nostril openings (nares) that is slit-like and oriented near horizontal, and positions 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 which may be a pheromone-like substance. Like other varanids, Bengal monitors have a forked tongue that is protruded in the manner of 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 greater rates of gas exchange and allows a faster metabolic rate and higher activity levels. Like all varanids, they have subpleurodont teeth, meaning the teeth are fused to the inside of the jaw bones. The teeth are placed one behind another, and there are replacement teeth behind and between each functional tooth (polyphyodont). The maxillary and dentary teeth are laterally compressed, sometimes with a slightly serrate cutting edge, while the premaxillary teeth are conical. There are 78 premaxillary teeth, 10 maxillary and 13 dentary teeth. Replacement teeth move forward and about four replacements happens each year for a tooth. Their mandibular glands produce secretions at the base of the teeth, and although some varanids have been shown to have a venom, no toxicity has been reported in the Bengal monitor.
, Afghanistan
, Pakistan
, India
, Nepal
, Sri Lanka
, Bangladesh
and Burma. The subspecies Varanus bengalensis nebulosus, the clouded monitor, occurs in southern Burma, Vietnam
, Cambodia
, Thailand
, Malaysia, Sumatra
, Java
and the Sunda Islands
. They have not been confirmed on Sumatra, and have been found to be absent from the Andaman Islands
.
The species is distributed mainly in the lower elevations, and is found both in dry semiarid desert habitats to moist forest. They are often found in agricultural areas, and are mainly found below 1500m altitude.
They are usually shy and avoid humans. They have keen eyesight and can detect human movement nearly 250 m away. When caught, a few individuals may bite, but rarely do so.
Captives have been known to live for nearly 22 years. Predators of adults include pythons, mammalian predators and birds. A number of ectoparasites and endoparasites are recorded.
Females may be able to retain sperm, and females held in confinement have been able to lay fertile eggs. Varanus niloticus has been demonstrated to be capable of parthenogenesis. The main breeding season is June to September. Males, however, begin to show combat behaviour in April. Females dig a nest hole in 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 of about 20 eggs are laid. The eggs hatch in 168 to nearly as long as 254 days. About 40 to 80% of the eggs may hatch.
and Bangladesh, and as ghorpad in Maharashtra
. Folk belief has it that they are venomous, and in Sri Lanka their breath is believed to be poisonous. In Rajasthan, they are believed to be venomous only during the rainy season. These lizards have strong claws they use for climbing. A popular legend has it that Shivaji's general, Tanaji Malusare
, used a monitor with ropes attached for climbing the walls of the Sinhagad
fort in the Battle of Sinhagad
. The Bengal Monitor's skin has traditionally been used in making the drum head for the Kanjira
, a South Indian percussion instrument.
Monitor lizards are hunted, and their body fat, extracted by boiling, is used in a wide range of folk remedies.
Monitor lizard
Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...
found widely distributed over South Asia
South Asia
South Asia, also known as Southern Asia, is the southern region of the Asian continent, which comprises the sub-Himalayan countries and, for some authorities , also includes the adjoining countries to the west and the east...
. This large lizard is mainly terrestrial
Cursorial
Cursorial is a biological term that describes an organism as being adapted specifically to run. It is typically used in conjunction with an animal's feeding habits or another important adaptation. For example, a horse can be considered a "cursorial grazer", while a wolf may be considered a...
, and grows to about 175 cm from the tip of the snout to the end of the tail. Young monitors may be more arboreal, but adults mainly hunt on the ground, preying mainly on arthropods, but also taking small terrestrial vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s, ground bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s, egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
s and fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
. Although large monitors have few predators apart from humans who hunt them for meat, younger individuals are hunted by many predators.
Description
The Bengal monitor has been said to reach nearly 175 cm with a snout-to-vent length (SVL) of 75 cm and a tail of 100 cm. Males are generally larger than females. Heavy individuals may weigh nearly 7.2 kg. The populations of India and Sri Lanka differ in the scalation from those of Myanmar, and these were once considered two species, but now considered two subspecies. The nominate subspecies is found west of Myanmar, while nebulosus is found to the east. The subspecies nebulosus is diagnosed by the presence of a series of enlarged scales in the supraocular region. The number of ventral scales varies, decreasing from 108 in the west (Pakistan) to 75 in the east (Java).Young monitor lizards are more colourful than adults. Young have a series of dark crossbars on the neck, throat and back. The 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 colour becomes light brown or grey, and dark spots give them a speckled appearance. Hatchlings of nebulosus tend to have a series of backward-pointing, V-shaped bands on their necks.
Bengal monitors have external nostril openings (nares) that is slit-like and oriented near horizontal, and positions 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 which may be a pheromone-like substance. Like other varanids, Bengal monitors have a forked tongue that is protruded in the manner of 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 greater rates of gas exchange and allows a faster metabolic rate and higher activity levels. Like all varanids, they have subpleurodont teeth, meaning the teeth are fused to the inside of the jaw bones. The teeth are placed one behind another, and there are replacement teeth behind and between each functional tooth (polyphyodont). The maxillary and dentary teeth are laterally compressed, sometimes with a slightly serrate cutting edge, while the premaxillary teeth are conical. There are 78 premaxillary teeth, 10 maxillary and 13 dentary teeth. Replacement teeth move forward and about four replacements happens each year for a tooth. Their mandibular glands produce secretions at the base of the teeth, and although some varanids have been shown to have a venom, no toxicity has been reported in the Bengal monitor.
Distribution and habitat
The species ranges from Iran to Java, among the most widely distributed of varanid lizards. It is found in river valleys in eastern IranIran
Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...
, Afghanistan
Afghanistan
Afghanistan , officially the Islamic Republic of Afghanistan, is a landlocked country located in the centre of Asia, forming South Asia, Central Asia and the Middle East. With a population of about 29 million, it has an area of , making it the 42nd most populous and 41st largest nation in the world...
, Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
, India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, Nepal
Nepal
Nepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...
, Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...
, Bangladesh
Bangladesh
Bangladesh , officially the People's Republic of Bangladesh is a sovereign state located in South Asia. It is bordered by India on all sides except for a small border with Burma to the far southeast and by the Bay of Bengal to the south...
and Burma. The subspecies Varanus bengalensis nebulosus, the clouded monitor, occurs in southern Burma, Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
, Cambodia
Cambodia
Cambodia , officially known as the Kingdom of Cambodia, is a country located in the southern portion of the Indochina Peninsula in Southeast Asia...
, Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
, Malaysia, Sumatra
Sumatra
Sumatra is an island in western Indonesia, westernmost of the Sunda Islands. It is the largest island entirely in Indonesia , and the sixth largest island in the world at 473,481 km2 with a population of 50,365,538...
, Java
Java
Java is an island of Indonesia. With a population of 135 million , it is the world's most populous island, and one of the most densely populated regions in the world. It is home to 60% of Indonesia's population. The Indonesian capital city, Jakarta, is in west Java...
and the Sunda Islands
Sunda Islands
The Sunda Islands are a group of islands that form part of the Malay archipelago.They are further divided into the Greater Sunda Islands and the Lesser Sunda Islands.-Administration:...
. They have not been confirmed on Sumatra, and have been found to be absent from the Andaman Islands
Andaman Islands
The Andaman Islands are a group of Indian Ocean archipelagic islands in the Bay of Bengal between India to the west, and Burma , to the north and east...
.
The species is distributed mainly in the lower elevations, and is found both in dry semiarid desert habitats to moist forest. They are often found in agricultural areas, and are mainly found below 1500m altitude.
Ecology and behaviour
Bengal monitors are usually solitary and usually found on the ground, although the young are often seen on trees. V. b. nebulosus has a greater propensity for tree climbing. Bengal monitors shelter in burrows they dig or crevices in rocks and buildings, whilst clouded monitors prefer tree hollows. Both races will make use of abandoned termite mounds. Bengal monitors, like other varanids, show true 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.They are usually shy and avoid humans. They have keen eyesight and can detect human movement nearly 250 m away. When caught, a few individuals may bite, but rarely do so.
Captives have been known to live for nearly 22 years. Predators of adults include pythons, mammalian predators and birds. A number of ectoparasites and endoparasites are recorded.
Breeding
Females may be able to retain sperm, and females held in confinement have been able to lay fertile eggs. Varanus niloticus has been demonstrated to be capable of parthenogenesis. The main breeding season is June to September. Males, however, begin to show combat behaviour in April. Females dig a nest hole in 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 of about 20 eggs are laid. The eggs hatch in 168 to nearly as long as 254 days. About 40 to 80% of the eggs may hatch.
Locomotion
They are capable of rapid movement on the ground. Small individuals may climb trees to escape, but larger ones prefer to escape on the ground. They can climb well. On the ground, they 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.Food
Large adults may ascend vertical tree trunks, where they sometimes stalk and capture roosting bats. Their normal prey consists of beetles, grubs, orthopterans, scorpions, snails, ants and other invertebrates. Vertebrate prey is comparatively rare, and includes frogs, fish, lizards, snakes and rodents. They sometimes feed on dead animals. In areas where livestock are common, they often visit dung, where they forage for beetles and other insects.In culture
The lizard is known as bis-cobra in western India, guishaap or goshaap in West BengalWest Bengal
West Bengal is a state in the eastern region of India and is the nation's fourth-most populous. It is also the seventh-most populous sub-national entity in the world, with over 91 million inhabitants. A major agricultural producer, West Bengal is the sixth-largest contributor to India's GDP...
and Bangladesh, and as ghorpad in Maharashtra
Maharashtra
Maharashtra is a state located in India. It is the second most populous after Uttar Pradesh and third largest state by area in India...
. Folk belief has it that they are venomous, and in Sri Lanka their breath is believed to be poisonous. In Rajasthan, they are believed to be venomous only during the rainy season. These lizards have strong claws they use for climbing. A popular legend has it that Shivaji's general, Tanaji Malusare
Tanaji Malusare
Tanaji Malusare , also known as Simha , was a warrior and military leader in the army of Shivaji, founder of the Maratha Empire in 17th century India. Tanaji was one of Shivaji's closest friends; the two had known each other since childhood....
, used a monitor with ropes attached for climbing the walls of the Sinhagad
Sinhagad
Sinhagad, Sinhgarh, or Sinhgad , is a fortress located roughly 30 kilometres southwest of the city of Pune, India. Previously called Kondhana , the fort has been the site of many important battles, most notably the battle of Sinhagad in 1670...
fort in the Battle of Sinhagad
Battle of Sinhagad
The Battle of Sinhagad was a night battle that took place on February 4, 1670 in the fort of Sinhagad, near the city of Pune, Maharashtra, India. It was fought between Tanaji Malusare, a commander of Maratha ruler Shivaji and Udaybhan Rathod, fortkeeper under Jai Singh I...
. The Bengal Monitor's skin has traditionally been used in making the drum head for the Kanjira
Kanjira
The kanjira, khanjira or ganjira, a South Indian frame drum, is an instrument of the tambourine family. It is used primarily in concerts of Carnatic music as a supporting instrument for the mridangam...
, a South Indian percussion instrument.
Monitor lizards are hunted, and their body fat, extracted by boiling, is used in a wide range of folk remedies.