Varanus griseus
Encyclopedia
The Desert Monitor, Varanus griseus, is a species of monitor lizard
of the order Squamata
found living throughout North Africa
and western Asia
. Varanus griseus is divided into three distinct subspecies: Varanus griseus griseus (Grey Monitor), Varanus griseus caspius (Caspian Monitor), and Varanus griseus koniecznyi (Indian Desert Monitor). They are possibly as venomous as snakes, and they eat anything from beetles to cobras and vipers depending on their size. Varanus griseus is not comfortable in captivity and only rarely has successful breeding in captivity been documented.
s on its head, including supra-oculars are very small, granular, subequal. The scales on the upper surface are small, smooth or feebly keeled; those on the sides of the neck generally conical in adult specimens. Abdominal scales of the Desert Monitor are smooth, in 110 to 125 transverse series (counted from collar-fold to groin). Its caudal scales more or less distinctly keeled; no caudal crest. Greyish yellow, sometimes with more or less distinct brown cross bars on the back and tail and brown streaks along the sides of the neck. Young monitors have round yellow spots and dark brown cross bars and temporal and cervical streaks; a few brown lines across the snout and short vertical brown lines on the lower lip.
they are living in. Their coloration can be anywhere from simple grey (in desert-like ecosystems) to brilliantly colored (in areas with large amounts of plant growth). Their most common prey consists of lizards and snakes, but can branch out to include ground-nesting birds and other small mammals.
and India
, and have the smallest body of the three subspecies. They have been reported to possibly not go through the normal hibernation
period over the winter, but are still inactive and do not feed between December and March. Their normal diet consists mainly of invertebrates, but can also branch out to other lizards and small mammals.
from approximately September all the way to April. In April there is a mass exodus from their hibernation, and they become most active between the months of May through July. During the middle of the day, the lizards mainly stay in their burrows and only come to the desert surface in order to search for food. The monitor lizards require approximately three to four full hibernation periods (years) in order to reach their full size (approximately 55-65 cm excluding their tail) and at least three hibernation periods before they become sexually mature. The overall lifespan of Varanus griseus in the wild does not normally exceed approximately eight years in both males and females.
whose behaviors therefore depend on the outside temperatures. Many lizards become sluggish in cold weather and even may become inactive if the temperature decreases substantially. Their olfactory and nerve signals significantly slow down which severely limit the lizard from either catching potential prey or escaping from predators. The body temperature of Varanus griseus is directly proportional to its running speed between the temperatures of 21 and 37 degrees Celsius. Between those temperatures the running speed of the monitor lizard increases from a little over 1 meter/second at 21 degrees to approximately 3 meters/second at 37 degrees. Over 37 degrees Celsius its running speed does not increase, and below 21 degrees the lizards are extremely sluggish. If they are being pursued by a predator while their body temperature is less than 21 degrees, they will not flee but will instead hold their ground and become extremely aggressive. The more their body temperature drops, the more aggressive the lizards become. In contrast, they can easily run away from the threat if their body temperature is high enough to allow for rapid movements. The outside temperature does indeed play a big role in their behavior and body functions.
The body temperature of Varanus griseus depends mainly on the outside environment
(time of day, season, etc). Their internal temperatures begin warming up before they even leave their burrows through conductive heat gain, and their temperatures rapidly rise once they begin basking in the morning sun and reach their highest point in the noonday heat. The specific body temperature of Varanus griseus can vary depending on the average temperatures of the country they live in, but their maximum body temperature does not usually exceed 38.5 degrees Celsius even when basking in the sunlight. Male monitor lizards are generally more active and also have a higher average body temperature than their female counterparts. The body temperature of the lizards during hibernation is anywhere from 15 to 30.5 degrees Celsius, but in many areas the average body temperature during hibernation is around 16-18 degrees Celsius.
. The preferred prey of the species is mice, eggs, or fish, but it will also prey on smaller mammals, reptiles, birds, amphibians, insects, or other invertebrates if the opportunity is presented to them since they are not picky eaters.
in the Varanus genus is widely debated. It was previously thought that venom was unique to Serpentes and Heloderma. It was believed that the aftereffects of a Varanus bite were due to oral bacteria
alone, but recent studies have shown that there are most likely venom
glands in the mouth of several, if not all of the species. Varanus griseus has not yet been specifically tested, but its bites have shown consistent aftereffects with the venomous bites from other Varanid lizards. The venom
can be used as a defensive mechanism to fend off predators, to help digest food, to sustain oral hygiene, and to possibly help in capturing and killing prey.
, although much of the land previously inhabited by the subspecies Varanus griseus caspius has been turned into farmland which puts pressure on the species. It is estimated that approximately 17,000 skins of this lizard are involved in commercial trade every year. Trading the skins internationally is prohibited by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). In northern Africa, central Asia, and parts of India however, the species is unprotected from hunting laws and is still hunted commercially.
Morocco, Algeria, Tunisia, Libya, Egypt, Palestine, Israel, Syria,
Lebanon, Iraq, Arabia, Oman, Turkmenistan, Kazakhstan, Uzbekistan,
Tajikistan, Kyrgyzstan
Western Sahara, Mauritania, Mali, Niger, Chad, Sudan,
Afghanistan, Iran (including Kavir desert), Pakistan, NW India
Type locality: Dardsha, coast of the Caspian Sea
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...
of the order Squamata
Squamata
Squamata, or the scaled reptiles, is the largest recent order of reptiles, including lizards and snakes. Members of the order are distinguished by their skins, which bear horny scales or shields. They also possess movable quadrate bones, making it possible to move the upper jaw relative to the...
found living throughout North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
and western Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
. Varanus griseus is divided into three distinct subspecies: Varanus griseus griseus (Grey Monitor), Varanus griseus caspius (Caspian Monitor), and Varanus griseus koniecznyi (Indian Desert Monitor). They are possibly as venomous as snakes, and they eat anything from beetles to cobras and vipers depending on their size. Varanus griseus is not comfortable in captivity and only rarely has successful breeding in captivity been documented.
Body Features
The teeth of Varanus griseus are acute and compressed. Its snout is depressed at the end, as long as the distance from the anterior border of the orbit to anterior border of the ear; canthus rostralis distinct. Its nostril is an oblique slit, about four times as distant from end of the snout as from orbit. Digits are rather short. Tail round or slightly compressed. The scaleReptile scales
Reptile skin is covered with scutes or scales which, along with other characteristics, distinguish reptiles from animals of other classes . Scales are made of keratin and are formed from the epidermis...
s on its head, including supra-oculars are very small, granular, subequal. The scales on the upper surface are small, smooth or feebly keeled; those on the sides of the neck generally conical in adult specimens. Abdominal scales of the Desert Monitor are smooth, in 110 to 125 transverse series (counted from collar-fold to groin). Its caudal scales more or less distinctly keeled; no caudal crest. Greyish yellow, sometimes with more or less distinct brown cross bars on the back and tail and brown streaks along the sides of the neck. Young monitors have round yellow spots and dark brown cross bars and temporal and cervical streaks; a few brown lines across the snout and short vertical brown lines on the lower lip.
Varanus griseus griseus
The Varanus griseus griseus subspecies (Grey Monitor) has 5-8 narrow grey bands on the back as well as 19-28 bands on the tail. Its tail is more rounded that those of the other subspecies and the final size of the adults depends on the habitatHabitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
they are living in. Their coloration can be anywhere from simple grey (in desert-like ecosystems) to brilliantly colored (in areas with large amounts of plant growth). Their most common prey consists of lizards and snakes, but can branch out to include ground-nesting birds and other small mammals.
Varanus griseus caspius
The Varanus griseus caspius subspecies (Caspian Monitor) has 5-8 bands on the back, 13-19 bands on the tail, a plain tail tip, and approximately 143 rows of scales in the middle section of their body. They have the largest bodies of the three subspecies, and are considered to be in danger of becoming extinct. They are found in mainly sandy or clay environments, although sporadically in sparse woodland areas. Their diet includes tortoises and their eggs, small mammals, along with adult cobras and vipers. They are strong diggers and can easily build burrows that are several feet long.Varanus griseus koniecznyi
The Varanus griseus koniecznyi subspecies (Indian Desert Monitor) has 3-5 bands on its back, 13-19 bands on the tail, a plain tail tip, 108-139 rows of scales on their midsection, and a broader and flatter head when compared to the other subspecies. They are mainly found in PakistanPakistan
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...
and 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...
, and have the smallest body of the three subspecies. They have been reported to possibly not go through the normal hibernation
Hibernation
Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...
period over the winter, but are still inactive and do not feed between December and March. Their normal diet consists mainly of invertebrates, but can also branch out to other lizards and small mammals.
Lifestyle
The Varanus griseus species goes into hibernationHibernation
Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...
from approximately September all the way to April. In April there is a mass exodus from their hibernation, and they become most active between the months of May through July. During the middle of the day, the lizards mainly stay in their burrows and only come to the desert surface in order to search for food. The monitor lizards require approximately three to four full hibernation periods (years) in order to reach their full size (approximately 55-65 cm excluding their tail) and at least three hibernation periods before they become sexually mature. The overall lifespan of Varanus griseus in the wild does not normally exceed approximately eight years in both males and females.
Importance of Body Temperature
Varanus griseus is a cold blooded ectothermEctotherm
An ectotherm, from the Greek εκτός "outside" and θερμός "hot", refers to organisms that control body temperature through external means. As a result, organisms are dependent on environmental heat sources and have relatively low metabolic rates. For example, many reptiles regulate their body...
whose behaviors therefore depend on the outside temperatures. Many lizards become sluggish in cold weather and even may become inactive if the temperature decreases substantially. Their olfactory and nerve signals significantly slow down which severely limit the lizard from either catching potential prey or escaping from predators. The body temperature of Varanus griseus is directly proportional to its running speed between the temperatures of 21 and 37 degrees Celsius. Between those temperatures the running speed of the monitor lizard increases from a little over 1 meter/second at 21 degrees to approximately 3 meters/second at 37 degrees. Over 37 degrees Celsius its running speed does not increase, and below 21 degrees the lizards are extremely sluggish. If they are being pursued by a predator while their body temperature is less than 21 degrees, they will not flee but will instead hold their ground and become extremely aggressive. The more their body temperature drops, the more aggressive the lizards become. In contrast, they can easily run away from the threat if their body temperature is high enough to allow for rapid movements. The outside temperature does indeed play a big role in their behavior and body functions.
The body temperature of Varanus griseus depends mainly on the outside environment
Environment
In general, environment refers to the surroundings of an object, or the Natural environment, all living and non-living things that occur naturally on EarthEnvironment may refer to:...
(time of day, season, etc). Their internal temperatures begin warming up before they even leave their burrows through conductive heat gain, and their temperatures rapidly rise once they begin basking in the morning sun and reach their highest point in the noonday heat. The specific body temperature of Varanus griseus can vary depending on the average temperatures of the country they live in, but their maximum body temperature does not usually exceed 38.5 degrees Celsius even when basking in the sunlight. Male monitor lizards are generally more active and also have a higher average body temperature than their female counterparts. The body temperature of the lizards during hibernation is anywhere from 15 to 30.5 degrees Celsius, but in many areas the average body temperature during hibernation is around 16-18 degrees Celsius.
Reproduction
Desert Monitor reproduction normally takes place between the months of May through July. Copulation occurs in May and June and the lizards normally lay their eggs from the latter part of June through the beginning of July. The eggs are incubated at temperatures from 29 to 31 degrees Celsius and hatch after an average of 120 days. At birth, the baby lizards have a total length of around 25 centimeters.Feeding, Hunting, and Diet
As with the almost every member of the Varanus genus, Varanus griseus is a carnivoreCarnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
. The preferred prey of the species is mice, eggs, or fish, but it will also prey on smaller mammals, reptiles, birds, amphibians, insects, or other invertebrates if the opportunity is presented to them since they are not picky eaters.
Venom
The possibility of venomVenom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
in the Varanus genus is widely debated. It was previously thought that venom was unique to Serpentes and Heloderma. It was believed that the aftereffects of a Varanus bite were due to oral bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
alone, but recent studies have shown that there are most likely venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
glands in the mouth of several, if not all of the species. Varanus griseus has not yet been specifically tested, but its bites have shown consistent aftereffects with the venomous bites from other Varanid lizards. The venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
can be used as a defensive mechanism to fend off predators, to help digest food, to sustain oral hygiene, and to possibly help in capturing and killing prey.
Conservation
Varanus griseus is not threatened in much of its habitatHabitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
, although much of the land previously inhabited by the subspecies Varanus griseus caspius has been turned into farmland which puts pressure on the species. It is estimated that approximately 17,000 skins of this lizard are involved in commercial trade every year. Trading the skins internationally is prohibited by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). In northern Africa, central Asia, and parts of India however, the species is unprotected from hunting laws and is still hunted commercially.
Captivity
These lizards rarely do well in captivity, and at most live only a handful of years there. On occasion when their living requirements can be specifically met they have been documented as living for more than 17 years while in captivity, although they never become docile and never become accustomed to being handled. In captivity their environments should mirror those of many ground dwelling animals as well as their natural desert habitat. They require lower temperatures in order to hibernate during the winter along with warmer temperatures during the summer months, and their diet in captivity is similar to their diet in the wild.Distribution
Jordan, Turkey (from Urfa) [Eiselt (1970), Böhme (1973)]Morocco, Algeria, Tunisia, Libya, Egypt, Palestine, Israel, Syria,
Lebanon, Iraq, Arabia, Oman, Turkmenistan, Kazakhstan, Uzbekistan,
Tajikistan, Kyrgyzstan
Western Sahara, Mauritania, Mali, Niger, Chad, Sudan,
Afghanistan, Iran (including Kavir desert), Pakistan, NW India
Type locality: Dardsha, coast of the Caspian Sea
