''Varanus scalaris'' is a small

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

monitor lizard Monitor lizards are lizards in the genus ''Varanus,'' the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and West African Nile monitor, one species is also found in south America as an invasive species. A ...

. It is often referred to as the banded tree monitor or the spotted tree monitor. It is found in

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

in the states of

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

and

Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

as well as the

Northern Territory The Northern Territory (abbreviated as NT; known formally as the Northern Territory of Australia and informally as the Territory) is an states and territories of Australia, Australian internal territory in the central and central-northern regi ...

, the province of Papua,

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

and in

Papua New Guinea Papua New Guinea, officially the Independent State of Papua New Guinea, is an island country in Oceania that comprises the eastern half of the island of New Guinea and offshore islands in Melanesia, a region of the southwestern Pacific Ocean n ...

. The species inhabits trees in the

savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) biome and ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach th ...

woodlands and forages for food in both trees and on the ground, with a diet consisting of insects as well as small vertebrates.

Venom

Like all other monitor lizards, banded tree monitors possess venom glands in their lower jaws, giving them a noticeably venomous bite. The venom is an

anticoagulant An anticoagulant, commonly known as a blood thinner, is a chemical substance that prevents or reduces the coagulation of blood, prolonging the clotting time. Some occur naturally in blood-eating animals, such as leeches and mosquitoes, which ...

, and has two known mechanisms for disrupting blood clotting: by fibrinogenolysis (the destructive cleavage of

fibrinogen Fibrinogen (coagulation factor I) is a glycoprotein protein complex, complex, produced in the liver, that circulates in the blood of all vertebrates. During tissue and vascular injury, it is converted Enzyme, enzymatically by thrombin to fibrin ...

) and by blocking

platelet Platelets or thrombocytes () are a part of blood whose function (along with the coagulation#Coagulation factors, coagulation factors) is to react to bleeding from blood vessel injury by clumping to form a thrombus, blood clot. Platelets have no ...

aggregation. The venom also causes

hypotension Hypotension, also known as low blood pressure, is a cardiovascular condition characterized by abnormally reduced blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood and is ...

. Monitor lizard venom is extremely complex and diverse due to the great range of

ecological niches In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for e ...

that they occupy. Banded tree monitors have the most potently fibrinogenolytic venoms of all monitor lizards, matched only by the similarly named tree monitors from the subgenus '' Hapturosaurus''. This may be because arboreal monitor species experience strong

selection pressure Evolutionary pressure, selective pressure or selection pressure is exerted by factors that reduce or increase reproductive success in a portion of a population, driving natural selection. It is a quantitative description of the amount of change oc ...

to quickly subjugate prey items before they break free and escape by falling out of the trees or flying away. As fibrinogenolytic activity is not painful, the venom likely has a primarily predatory role in subjugating prey, instead of acting as a predator deterrent. It is suggested that higher prey escape potential may cause increased venom potency, as the lethally toxic eastern green mamba and

boomslang The boomslang ( or ; ''Dispholidus typus'') is a highly venomous snake in the family Colubridae. The species is native to Sub-Saharan Africa. Etymology Its common name means "tree snake" in Dutch and Afrikaans – ''boom'' meaning "tree", and ...

are also arboreal. This may also apply to the

piscivorous A piscivore () is a carnivorous animal that primarily eats fish. Fish were the diet of early tetrapod evolution (via water-bound amphibians during the Devonian period); insectivory came next; then in time, the more terrestrially adapted rept ...

and highly venomous cone snails, given their highly mobile fish prey. As the venom is an anticoagulant, monitor lizard bites often bleed far more than what the mechanical damage of the bite alone would have induced. File:Varanus scalaris 188042299.jpg File:Varanus scalaris 20401701 (cropped).jpg File:Varanus scalaris 197143199.jpg File:Varanus scalaris 197142881 (cropped).jpg

References

{{Taxonbar, from=Q3554681 Varanus Lizards of Asia Monitor lizards of Australia Reptiles of Papua New Guinea Reptiles of Indonesia Reptiles of Queensland Reptiles of Western Australia Reptiles of the Northern Territory Reptiles described in 1941 Taxa named by Robert Mertens