Monitor Lizard genus Varanus Searching for food .
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Monitor lizard is the common name of several large lizard species, comprising the genus Varanus. They are native to Africa, Asia and Oceania, but are now found also in the Americas as invasive species.Monitor lizards have long necks, powerful tails and claws, and well-developed limbs. Their adult length ranges from 20 cm (7.9 in) in some species, to over 3 meters in the case of the Komodo dragon. Most species are terrestrial, but arboreal and semiaquatic monitors are also known. While most monitor lizards are carnivorous, eating eggs, smaller reptiles, fish, birds and small mammals, some also eat fruit and vegetation depending on where they live.A total of 73 species are currently recognized; however, given that several species-groups are in need of taxonomic review, this number is certain to be increased with future research.The various species cover a vast area, occurring through Africa, the Indian Subcontinent, to China, down Southeast Asia to Brunei, Indonesia, the Philippines, New Guinea, Australia and islands of the Indian Ocean, and the South China Sea. A large concentration of monitor lizards occurs on Tioman Island in the Malaysian state of Pahang. Some are now found in South Florida, particularly in the Everglades.Monitor lizards differ greatly from other lizards in several ways, possessing a relatively high metabolic rate for reptiles, and several sensory adaptations that benefit the hunting of live prey. Recent research indicates the varanid lizards may have some venom. This discovery of venom in monitor lizards, as well as in agamid lizards, led to the Toxicofera hypothesis: that all venomous lizards and snakes share a common venomous ancestor.During the late Cretaceous era, monitor lizards or their close relatives are believed to have evolved into amphibious and then fully marine forms, the mosasaurs, which reached lengths of up to 17 m.Snakes were believed to be more closely related to monitor lizards than any other type of extant reptile; however, it has been more recently proposed that snakes are the sister group of the clade of iguanians and anguimorphs.Like snakes, monitor lizards have forked tongues which they use to sense odors.During the Pleistocene epoch, giant monitor lizards lived in Southeast Asia and Australasia, the best known fossil being the megalania (Varanus priscus unless it falls in its own genus, in which case it is Megalania prisca). This species is an iconic member of the Pleistocene megafauna of Australia.Some monitor lizards, including the Komodo dragon, are capable of rthenogenesis.Varanid lizards are very intelligent, and some species can even count.Careful studies feeding V. albigularis at the San Diego Zoo varying numbers of snails showed they can distinguish numbers up to six.V. niloticus lizards have been observed to cooperate when foraging.One varanid lures the female crocodile away from her nest, while the other opens the nest to feed on the eggs.The decoy then returns to also feed on the eggs.Komodo dragons, V. komodoensis, at the National Zoo in Washington, D.C., recognize their keepers and seem to have distinct personalities.Monitor lizards have become a staple in the reptile pet trade. The most commonly kept monitors are the savannah monitor and Ackies monitor, due to their relatively small size, low cost, and relatively calm dispositions with regular handling.Monitor lizard meat, particularly the tongue and liver, is eaten in parts of southern India and Malaysia as an aphrodisiac.In parts of Pakistan, different parts of monitor lizards are used for a variety of medical purposes. The flesh is eaten for relief of rheumatic pain, abdominal fat is used as a salve for skin infections, oil and fat are used to treat hemorrhoids or chronic pain, and the oil is used as an aphrodesiac lubricant."Large scale exploitation" of monitor lizards is undertaken for their skins, which are described as being "of considerable utility" in the leather industry.The meat of monitor lizards are eaten by some tribes in Pakistan, India, Thailand and in West Africa as a supplemental meat source.All but five species of monitor lizard are classified by the Convention on International Trade in Endangered Species of Wild Fauna and Flora under Appendix II, which is loosely defined as species that are not necessarily threatened with extinction, but may become so unless trade in such species is subject to strict regulation order to avoid use incompatible with the survival of the species in the wild. In Tamil Nadu and all other parts of South India, catching or killing of monitor lizards is banned under the Protected Species Act.