Reptiles and Amphibians

Reptiles and Amphibians book cover — FACTS AT YOUR FINGERTIPS ENDANGERED ANIMALS REPTILES AND AMPHIBIANS BROWN BEAR BOOKS

Reptiles and Amphibians — page 1 — What is a Reptile like like all classes of animal reptiles are divided into groups crocodilians lizards the tuatara snakes and chelonians tortoises and turtles All reptiles are said to be cold blooded More correctly they are ectothermic which means that unlike mammals and birds they cannot produce heat inside the body but rely instead on heat from external sources mainly sunlight to raise their body temperatures When their bodies have warmed up sufficiently they are able to engage in normal activities such as feeding The ectothermic reptiles need less food and have colonized deserts where food is scarce as well as every other type of habitat except where the land is permanently frozen Birds are covered in feathers and mammals are covered in hair but reptiles have a covering of scales The Senegal chameleon below of West Africa Chameleons are one of a number of reptiles that have evolved to follow a specialized lifestyle and seldom manage to adapt to changed conditions 4 although in some cases the scales are so small and smooth that they resemble skin Reptiles have developed numerous shapes sizes colors and other features that enable them to live in their own particular niche Although some species may be able to adapt to a changed habitat many depend on a particular habitat and conditions marine turtles and some freshwater turtles are totally aquatic leaving the water only to lay eggs Some aquatic species can only feed in water although they spend much of their time on land see yellow blotched sawback map turtle pp 16 17 Lizards show much more variation in body form than other reptiles some forms are long and snakelike with no limbs others may have only two limbs Among the lizards there are burrowing species that hardly ever come above ground The speed of movement of reptiles varies tortoises are generally slow moving creatures that rely on withdrawing into their shell for protection and are easy to capture Some lizards are slow moving but capable of a quick burst of speed others are agile and quick moving Among the snakes and lizards The green sea turtle above and its eggs have long been eaten by humans In recent years it has faced an increasing number of human made threats to its survival several different lifestyles exist some are aquatic others terrestrial or arboreal and there are also semiaquatic and burrowing forms Many reptiles hide in disused animal burrows or dig their own Some shelter under rocks or logs and others burrow or shuffle into the soil for shelter Many reptiles are actually beneficial to farmers and gardeners because they eat large

Reptiles and Amphibians — page 2 — numbers of insects others predate rodents thus keeping numbers down The History of Reptiles The earliest reptiles known from fossilized remains are estimated to have lived 315 million years ago In the millions of years that followed a multitude of different forms evolved Those that survived when the dinosaurs died out gradually developed into the forms we see today Two reptile groups the crocodilians and the chelonians have changed little in 65 million years apart from now being smaller than their ancestral forms Since 1600 21 forms have become extinct and 454 forms are threatened Why are Reptiles at Risk The decline of a particular species may be due to a combination of causes but the greatest single threat to all animals is habitat destruction The lifestyles and characteristics of reptiles make them vulnerable to many of the human-made threats Habitat destruction takes numerous forms such as land clearance and most reptile species cannot adapt to changed habitat Land can be cleared by tree-felling burning or large-scale construction machinery Arboreal reptiles suffer from the loss of trees For example chameleons are threatened in many regions by deforestation They are superb examples of adaptation to arboreal life with their divided feet and prehensile tails Only a few species manage to adapt to living in secondary forest which sometimes grows when farm land has been abandoned If the land has been turned over to crops or cattle the original vegetation disappears Unless there is suitable habitat nearby into which reptiles can move if they have not been killed during land clearance they begin to die out Although fires can be natural they are a threat particularly to slow-moving animals such as desert tortoises and geometric tortoises but in some cases the creatures may survive by sheltering in burrows for example eastern indigo snakes WHAT IS A REPTILE However in some areas notably Madagascar and Indonesia deliberate burning that can get out of control is causing devastation to plants and animals Deforestation leads to soil erosion especially along river banks and destroys nesting areas of many freshwater turtles for example pig-nosed turtles In turn soil erosion leads to the silting up of rivers necessitating dredging equipment to clear and deepen the water which disturbs their habitat further Silt carried out to sea destroys coral reefs where some marine turtles feed In some countries land along river banks has been cleared for housing thus bringing the native people into conflict with aquatic reptiles see gharial pp 30 31 Modern construction equipment can quickly alter large areas of habitat destroying any creatures that do not move fast enough Reptiles that are hibernating estivating or simply sheltering are vulnerable to land clearance Since life appeared on earth many animal species have become extinct like these various types of giant land and sea reptiles Extinctions are part of the natural process but the impact of human population increase has accelerated the dangers facing many species 5

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