![]() Some monitor lizards, including the Komodo dragon, are capable of parthenogenesis. Monitor lizards are oviparous, laying from seven to 38 eggs, which they often cover with soil or protect in a hollow tree stump. The venom of monitor lizards is diverse and complex, as a result of the diverse ecological niches monitor lizards occupy. This allows monitor lizards to create mammalian-equivalent pressure differentials between the pulmonary and systemic circuits, which in turn ensure that oxygenated blood is quickly distributed to the body without also flooding the lungs with high-pressure blood.Īnatomical and molecular studies indicate that all varanids (and possibly all lizards) are partially venomous. Whereas most reptiles are considered to have three-chambered hearts, the hearts of monitor lizards – as with those of boas and pythons – have a well developed ventricular septum that completely separates the pulmonary and systemic sides of the circulatory system during systole. Monitor lizards have a high aerobic scope that is afforded, in part, by their heart anatomy. The forked apparatus allows for these lizards to sense boundaries in the molecules they collect, almost smelling in "stereo". Like snakes, monitor lizards have highly forked tongues that act as part of the "smell" sense, where the tips of the tongue carry molecules from the environment to sensory organs in the skull. The general consensus is that monitor lizards have the highest standard metabolic rates of all extant reptiles. The active nature of monitor lizards has led to numerous studies on the metabolic capacities of these lizards. Monitor lizards maintain large territories and employ active-pursuit hunting techniques that are reminiscent of similar-sized mammals. Finer morphological features such as the shape of the skull and limbs do vary, though, and are strongly related to the ecology of each species. The genus Varanus is considered unique among animals in that its members are relatively morphologically conservative, yet show a very large size range. Although normally solitary, groups as large as 25 individual monitor lizards are common in ecosystems that have limited water resources. In contrast, three arboreal species from the Philippines, Varanus bitatawa, Varanus mabitang, and Varanus olivaceus, are primarily fruit eaters. Deer make up about 50% of the diet of adults of the largest species, Varanus komodoensis. Most species feed on invertebrates as juveniles and shift to feeding on vertebrates as adults. Most monitor lizards are almost entirely carnivorous, consuming prey as varied as insects, crustaceans, arachnids, myriapods, mollusks, fish, amphibians, reptiles, birds, and mammals. Monitor lizards also occurred widely in Europe in the Neogene, with the last known remains in the region dating to the Middle Pleistocene. The West African Nile monitor ( Varanus stellatus) is now found in South Florida. The various species cover a vast area, occurring through Africa, the Indian subcontinent, to China, the Ryukyu Islands in southern Japan, south to Southeast Asia to Thailand, Malaysia, Brunei, Indonesia, the Philippines, New Guinea, Australia, and islands of the Indian Ocean and the South China Sea. While most monitor lizards are carnivorous, eating eggs, smaller reptiles, fish, birds, insects, and small mammals, some also eat fruit and vegetation, depending on where they live. Most monitor species are terrestrial, but arboreal and semiaquatic monitors are also known. ![]() The adult length of extant species ranges from 20 cm (7.9 in) in some species such as Varanus sparnus, to over 3 m (10 ft) in the case of the Komodo dragon, though the extinct varanid known as megalania ( Varanus priscus) may have reached lengths of more than 7 m (23 ft). Monitor lizards have long necks, powerful tails and claws, and well-developed limbs. They are native to Africa, Asia, and Oceania, and one species is also found in the Americas as an invasive species. Monitor lizards are lizards in the genus Varanus, the only extant genus in the family Varanidae. ![]() ![]() ![]() Combined native range of all the monitor lizards ![]()
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