Excerpts

Preface Amphibians and reptiles form two separate classes of animals, even though they are traditionally studied together, a situation that arose partly because the distinctions were not well understood in the early days of the science -- Linnaeus placed the European smooth newt and the Viviparous lizard in the same genus, for instance. In practice, it is still convenient to study them jointly because they often live in the same places, and searching for them often involves the same techniques. The study of reptiles and amphibians is known as herpetology, from the Greek word herpeto, meaning "to creep." Herpetologists may study reptiles, amphibians, or both and, even if they study one class, they tend to have an interest in the other one as well. In the early days of zoology -- the 18th and early 19th centuries -- herpetology had a smaller following than other biological disciplines such as ornithology or botany. Part of the reason lies in distribution patterns, with reptiles and amphibians tending to be most numerous in the parts of the world where scientists were least numerous, notably South America, Africa, Southeast Asia, and Australasia. In Europe and temperate North America, the traditional seats of learning, they are absent for much of the year. On top of this, they are usually inedible, if not downright poisonous, and therefore had little economic importance compared with fish, birds, mammals, and plants. And, it must be said, some of them are not beautiful in the conventional sense of the word; at least, not in the eye of the uninformed. Little wonder, then, that the naturalists of the 18th and 19th centuries did not think they played a very important part in the grand scheme of things. Linnaeus called them "foul and loathsome creatures," while Charles Darwin described the marine iguana as a "hideous-looking creature, of a dirty black colour, stupid, and sluggish in its movements." Although some species are still the objects of fear, superstition, and prejudice, for the most part attitudes changed gradually through the 20th century, influenced by studies such as those by Laurence Klauber on rattlesnakes, Archie Carr's pioneering work on turtles, and the appearance of some excellent field guides and other publications, both popular and scientific. Reptiles and amphibians began to be studied in their own right, not necessarily because they were useful (although it turned out that some of them were) but because they were interesting and often attractive animals. Furthermore, because they are relatively easy to house and observe in captivity, reptiles and amphibians often make good subjects for studies whose implications spill over into other branches of the biological sciences. Through the media of books, photography, and film, there is a growing appreciation nowadays of the ways in which they have adapted to a variety of different environments, notably rain forests, where amphibian and reptile diversity reaches its greatest heights, and in deserts, where reptiles -- especially lizards -- are often the most obvious, or only, form of vertebrate life. Inherent variation in lifestyle has much to do with their success. To name just a few of these variables, reptiles and amphibians may be oviparous or viviparous; several are parthenogenetic; and many species can shut down their physiological systems for long periods of time to avoid prolonged heat, cold, or drought. Reptiles are the only vertebrates that can uncouple the activities of mating and fertilization, allowing females to store sperm for weeks, months, or even years in some cases, while many amphibians have developed breeding systems that enable them to become independent of standing water. This book discusses all these subjects, and more. On the one hand it follows the traditional threads that represent the taxonomic units and the way in which species, genera, and families are arranged into hierarchical groups depending on their similarities and differences -- the science of taxonomy. There is an extensive introduction to each of the two classes, describing their origins and giving an overview of their biology. Within each class, separate accounts of the three orders of amphibians and the four orders of reptiles deal in more detail with their specific biology and provide interesting facts about their members, and there is a short description of each family. The accounts of the six largest groups are summarized with annotated lists of the families, giving statistics for the numbers of species and genera, their most important characteristics, some examples, and a distribution map. Superimposed on this outline plan are other threads, which cut across the taxonomic divisions and subdivisions and deal with the disciplines of anatomy, physiology, ecology, and behavior, subjects that are common to all species, including other animals, thus emphasizing their similarities as well as their differences. Throughout the book there are also articles on topics of special interest. These may be double-page spreads or smaller boxes, and they highlight aspects of the study of reptiles and amphibians that have made herpetology an increasingly important discipline within zoology as a whole. They can be read independently of the rest of the text. In addition, captions to many of the diagrams and photographs are extensive, and give interesting snippets of information to supplement the other material. Recent developments in the techniques by which animals can be studied have given our understanding of reptiles and amphibians new impetus. Advances in DNA technology and other types of biochemical analyses, for example, are helping to solve many of the puzzles surrounding their relationships. All this takes time but, as each unit -- species, genus, family, order -- is investigated, new schemes, such as that recently established for a radical system of frog classification, will occur across the board. The classification of the Colubridae, a family that accounted for an unlikely 60 percent of all snakes in the previous division, springs to mind as an example of one group of species whose relationships are beginning to be better understood; the colubrids are now divided into four distinct families and many subfamilies, some of which will undoubtedly be elevated to full families at some point in the future. While this and similar puzzles are being solved in the laboratory, field workers are benefiting from the technological revolution in electronics, where miniaturization and telemetry give them the tools to track animals that spend a large part of their time out of sight. Activities and social interactions that were previously unknown, or mere guesswork, are now being monitored, and the resulting information is fascinating; amphibians and reptiles are not the mindless creatures that many people thought they were but often lead complex and effective lives to ensure their survival. Unfortunately, animals whose survival strategies have evolved over thousands of generations and in response to gradual changes, are ill equipped to deal with the sudden and dramatic changes that are occurring now. In the previous editions of this book, the authors and editors frequently stressed the dangers facing reptiles and amphibians and the need for conservation. Since the previous editions, the situation has deteriorated further. A steady stream of reptiles and amphibians are going extinct in most parts of the world. More than 20 species of reptiles have gone in living memory, due to habitat destruction and competition and predation from introduced species, especially domestic animals. Another 530 species are either Endangered or Critically Endangered, and many species that used to be common are now scarce and their populations fragmented. Amphibians are the worst affected, for reasons that are discussed elsewhere, and the statistics speak for themselves. The IUCN estimates that 789 species of amphibians are Endangered, another 518 are Critically Endangered, 36 have recently gone extinct. This total of 1,343 represents a staggering 18 percent of all Excerpted from Firefly Encyclopedia of Reptiles and Amphibians All rights reserved by the original copyright owners. 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