Monitors are a small but diverse group of lizards. They have been around for at least seventy million years, have probably lived on all of the Earth's continents and are still present in three of them. Monitor lizards are carnivorous and generally feed on any animals they are able to swallow. The family includes the largest lizards that have ever walked the Earth. But whilst some are gigantic creatures capable of preying on man, others are so small they have difficulty overpowering anything much larger than an grasshopper. Some of the largest lizards that ever walked the Earth still alive today. Most monitor lizards are only active during the day and all reproduce by laying eggs, but they employ a wide variety of reproductive strategies. The monitors show astonishing variation in size. diet, behaviour and habitat, and are a marvellous example of how one tiny group of animals have adapted to suit many different environments.
The smallest monitor lizard reaches a total length of only 20 cm and a weight of less than 0.05kg (50g). The heaviest monitor weighs as much as 250kg. The longest monitor lizard has a supposed total length of over 470cm. Monitor lizards inhabit areas which are among the driest and wettest places on Earth and are often present in large numbers. They are found in deserts. on seashores, in woodlands, grasslands, rivers, lakes, swamps and rainforests. Monitor lizards are extremely important to the economy of people, acting both as pest controllers and as a source of meat and leather. Some monitor lizards have been almost completely unaffected by the emergence of mankind (a few have even benefited from it), but others have suffered extermination to the point that it is reasonable to suppose they will be have vanished from the wild before the end of the next century. Despite their size and their ecological and economic importance, the monitor lizards have not been given the attention they deserve by biologists. In recent years the siruation has improved greatly, but even now virtually nothing is known of the ecology of many species, including some of the largest ones.
The purpose of this book is to surrunarise what is known about the way of life of monitor lizards in the wild, and how that knowledge may be applied to their captive propagation. Monitor lizard can be extremely rewarding animals to keep in captivity but, in my opinion. there is little point in keeping wild animals confined if they do not reproduce. The day may come when some of the monitor lizards will disappear for ever if they cannot be bred in captivity. Even small scale propagation of some species could make a significant contribution to their overall populations as well as providing important clues to their life history in nature. In the animal trade captive bred examples of even the commonest species are in great demand and fetch much higher prices than their wild counterparts, but they are all too seldom seen. For these reasons special emphasis has been put on the care of monitor lizards in captivity, and infonnation regarding their propagation is included wherever known. Again certain cases have been omitted either because they are suspect or impossible to verify and many more have been inadvertently overlooked. There is a wealth of unpublished data which would be of enonnous value to would-be varanid propagators. If you have experiences of keeping monitor lizards, good or bad, you should share them. Herpetologists are renown for being amongst the friendliest people in the world and herpetological societies provide an ideal way to meet, share ideas and learn from other enthusiasts. A list of some groups and societies with a special interest in monitor lizards is given at the end of the bibliography but isby no means comprehensive. Contacts for local societies can be found in magazines devoted to rertiles, or ask at a local zoo or museum.
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