Reptiles and Amphibians

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

Reptiles and Amphibians — page 3 — Lizards are probably the most familiar of the reptiles because of their diversity and wide distribution Examples include the ocellated green lizard 1 fat tailed gecko 2 western skink 3 1 blue-tongued skink 4 a sharp-snouted snake Pygopodidae 5 and Colorado checkered whiptail 6 3 4 2 6 5 The emerald boa above is threatened by the destruction of tropical rain forest since it feeds and gives birth in trees Destruction of habitats also removes huge numbers of insects which are an important part of the food chain and support other species of reptile especially lizards Plowing is particularly dangerous to creatures that live in isolated areas of grassland see pygmy blue-tongued skink pp 10 11 and plowing a field could possibly wipe out a whole population of a particular reptile species In addition since many reptiles bury their eggs they are destroyed by such activities Particularly vulnerable are those species that lay small clutches since it is more difficult for population numbers to increase for example Fijian crested iguanas and leopard snakes Farming and industry bring additional threats such as chemical pollution and waste products The effects of pollution are many and varied spraying insecticides for example wipes out the insects on which many lizards rely it can also directly poison reptiles see blunt-nosed leopard lizard pp 8 9 Turtles need clean unpolluted water while some can withstand a degree of certain types of pollution the danger is that the aquatic creatures on which they feed are wiped out Drainage of swamp areas for farming and building forces some species into an ever-decreasing habitat Habitats have become fragmented in many parts leaving a few isolated areas that prevent contact between populations see Jamaican boa pp 20 21 That causes inbreeding which eventually produces weaknesses deformities and reduced fertility in future 6

Reptiles and Amphibians — page 4 — generations further affecting survival Leisure activities affect reptiles many beaches used by marine turtles for thousands of years for nesting have disappeared under development see hawksbill turtle pp 14 15 Reptiles such as snakes and lizards are sometimes killed to avoid frightening tourists Off road vehicles cause great damage to the burrows and nests of reptiles see gila monster pp 32 33 Hunting and Exploitation Deliberate killing of some reptile species is quite common Many people believe that all reptiles are venomous although very few are in fact dangerous to humans Large reptiles such as alligators and crocodiles can however be dangerous to people and can prey on domestic livestock see Chinese alligator pp 26 27 American crocodile pp 28 29 so they are often killed They have also been regarded as big game and hunted for sport In many parts of the world some reptiles feature in the diet of the native people Where hunting is excessive it can be a serious threat to the survival of a species see Galápagos giant tortoise pp 18 19 Turtle eggs and some lizard eggs are taken for food which combined with other factors causes endangerment Exploitation includes the use of reptile skins and shells Huge numbers of reptiles are used in traditional medicine in various regions the rarer a creature is the more its value The pet trade is often accused of depleting reptile populations This may be true in some cases for example yellow blotched sawback map turtle pp 16 17 but controls on the trade are continually being tightened Despite this smuggling livestock for trade skins food and medicine still occurs in many regions of the world Threats to Island Populations Island populations are highly vulnerable to collection for food see Galápagos giant tortoise pp 18 19 destruction of their habitat see Milos viper pp 24 25 or competition for food see Komodo dragon WHAT IS A REPTILE A crocodile head ashtray This and similar grisly souvenirs are hardly essential to humans but many people are still tempted to buy them Often they are from an endangered creature and it is illegal to sell or import them in many countries pp 12 13 and natural disasters The vegetation of many islands has been eaten by introduced animals such as goats and pigs that escaped and reproduced with devastating results Rats cats and dogs colonized many islands Without any natural predators to keep numbers down they too have taken their toll of reptiles living in restricted island habitats see Jamaican boa pp 20 21 The Situation Today Extinction of some species is part of a natural process but it normally takes thousands or even millions of years Today with the growth of the human population extinction has speeded up and will no doubt accelerate further Although relatively few of the total number of reptile species are listed as Endangered many face similar threats to those that challenge their Endangered relatives Certain species such as the Galápagos land iguana Galápagos giant tortoise pp 18 19 and Komodo dragon pp 12 13 stand out more than others and their plight has made them the focus of well publicized conservation work Conservation attempts will continue but some species will become extinct because of the pressure on their habitats from expanding human populations Zoos and other institutions have limited space and funds and so must limit the creatures they keep Conservation in the wild is also restricted by funds and needs the support of local people It is often difficult to convince people that creatures they fear or dislike are worth saving but attitudes are slowly changing 7

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