World Habitat

In parts of the world where it is too dry for trees to grow, yet moist enough to prevent the land from becoming desert, grasses are the dominant plants. Grasses are unusual in that their stems grow from a point near the ground. This means that unlike most other plants, which grow from their tips, grasses are unharmed by grazing. In fact, grazing animals help grasses to maintain their dominance by stunning the growth of competing plants. This creates a vast, open habitat in which there is plenty of plant food – for those that can digest it – but little shelter from the dements.

• TEMPERATE GRASSLAND

Before the advent of farming, grassland covered large parts of the temperate world, notably in the northern hemisphere. These vast grasslands – which include the prairies of North America, and the steppes of Europe and central Asia – are nearly all in the center of large landmasses, far away from coasts and their moisture – laden winds. Summers are often warm, but winters can be long and cold, with biting winds. An unusual feature of this kind of habitat is that the majority of the plant matter is hidden away below ground – the exact opposite of the situation elsewhere on land. This is because grass plants direct much more energy into growing roots than into producing leaves, and their roots form a continuous mat, which protects the surface of the ground by holding the soil in place. If grassland is burned, or hit by drought, it can soon recover because the grass can draw on its buried reserves in order to start growing again. The most mat makes a useful source of food for insects and other small animals. It is also a perfect medium for burrowers, because it is easy to dig through and, unlike loose soil, rarely caves in. above ground, the food supply is closely tied to the water usually comes in the form of spring rain or melting snow. This creates a flush of growth during spring and early summer, which is the time that most grazing animals breed. By late summer, the grass is brown and dry, although for a while grass seeds make a valuable autumn harvest. Winter is difficult time for all grassland animals, but particularly for grazers because they often have to survive on low grade food that is hidden under snow. The largest areas of temperate grassland are found in North America, South America, eastern Europe, and eastern Asia.

• SAVANNA   

Savanna is tropical or subtropical grassland that contains scattered shrubs and trees. The grasslands of east Africa are a familiar example, with their diverse wildlife and distinctive vegetation (particularly the flat – topped acacia trees). Compared with temperate grassland, savanna is very variable; in some savanna habitats, trees are few and far between; in others, they form scattered thickets, merging into open woodland. Trees have a major impact on the savanna’s animal life. This is because they produce a wide variety of food, including wood, leaves, flowers, and seeds: and they also create shelter and breeding sites for animals that live off the ground. The balance between trees and grass is a delicate one that is sometimes changed by the animals themselves. For example, elephants destroy trees by pushing them over so that they can reach their leaves. However, elephants also help trees to reproduce because they ingest the trees’ seeds, which are then passed in their dung – an ideal medium for promoting seed growth. Browsing mammals often keep trees in check by nibbling saplings before they have had a chance to become established. Fire also helps to hold back trees, and its effect is most apparent in places where tees grow close together. Unlike temperate grassland habitats, savanna is usually warm all year round. There is often a long dry season, when most trees lose their leaves, followed by a wet, or “rainy” season, which produces a rapid burst of growth that turns the landscape green. During this wet season, plant – eating animals rarely have to contend with a shortage of food: In the dry season, the threat of starvation is never far away, and many animals travel long distances to find water and food. Savanna is found mainly in central and South America, tropical Africa, South Asia, and northern Australia.

• LIFE IN GRASSLAND

Despite centuries of human disturbance, grassland supports some of the largest concentrations of animal life on earth. Survival in grassland habitats is far from easy; however; aside from the lack of shelter and plant diversity, there are hazards such as drought and fire to contend with. Added to this is the ever – present risk of attack by some of the world’s fastest and most powerful predators.

• HERDING  

Life in open grassland is often dangerous because there are few places to hide. To increase their chance of survival, many large plant – eaters live in herds. This makes it more difficult for predators to attack because while most members of the herd are eating, some are always on the lookout for danger. Today’s largest herds are found on Africa’s plains. Here, migrating wildebeest can form herds over a quarter of a million strong, and 40km (25 miles) long, although even these herds are small compared with some that existed in the past. During the nineteenth century, springbok herds in southern Africa sometimes contained more than 10 million animals. In North America, bison herds probably reached similar sizes before hunting brought the species to the edge of extinction. Life in herds does have its problems, one of which is the risk that an animal might wander off and become lost. Most herding species have scent glands on their hooves so that if an animal becomes isolated it can follow the scent tracks to rejoin the herd. Another problem is giving birth. To prevent their young from being trampled, or attacked, many grazers give birth in cover, and rejoin the herd a few weeks later. Some, however, are born in the open and have to keep up with the herd when they are just a few hours old (Precocial).  

• MOVEMENT

In grassland and savanna, there is a premium on speed. It is no accident that the world’s fastest land animals, such as the cheetah and the pronghorn, are found in this habitat. Natural selection favors predators that are fast enough to catch food, and prey animals that are fast enough to escape. Most of the fast runners are mammals, however grassland also has nature’s fastest – running birds, including Ostriches, rheas, and emus- giant species that have lost the ability to fly. These birds can reach speeds of up to 70 kph (44 mph). More importantly, they are able to maintain such speeds for up to 30 minutes – long enough to outrun most of the enemies unless a predator launches an attack from a very close range. Despite the many fast runners, grassland life often appears tranquil. This is because running is extremely energy – intensive, and animals run only when they absolutely have to. Prey animals have invisible “security thresholds

“that vary according to the threat they face. For example, gazelles often let lions approach to within about 200 m (650 ft) because they are Instinctively aware that lions that are visible at this distance are unlikely to be stalking prey. A solitary cheetah, on the other hand, will send a gazelle herd sprinting, even if it is seen to be four times further away.

• LIVING UNDER GROUND

Some grassland animals find safety not by running away but in retreating into burrows below ground. There they can stay out of reach of most predators and find some protection from the worst of the elements. Subterranean animals include a wide variety of species, ranging from mammals to insects. Some animals, particularly snakes, do not excavate their own burrows, instead they adopt existing ones. The largest burrows, made by African aardvarks, are big enough to accommodate a person, and are a serious hazard to vehicles; the most extensive are made by prairie dogs and other rodents. Before farming became widespread in North America’s prairies, some prairie – dog burrow systems covered several thousand square kilometers and housed millions of animals. Termites are also accomplished builders, constructing giant, elaborate, subterranean nests that extend high above ground level. These nests house large, co – operative communities that can contain over 30 million inhabitants. Along with ants, they make up a very large part of the habitat’s animal life, and provide food for the large – insect – eaters.

• FEEDING

Although grass is rich in nutrients and easy to find, it is difficult to digest. Many mammals, including humans, cannot break it down at all because it contains large amounts of cellulose – a carbohydrate that most animals cannot digest. Grazing mammals, however, have special micro – organisms in the gut that break down cellulose so that the body is able to use it. Some non – mammal species also use microbes to digest plant material. In tropical savanna, for example, termites rely on them to break down dead leaves and wood. The animals that are more efficient at using cellulose are ruminant mammals (cud – chewers/ 4 chambered stomach mammals) of the family Bovidae (Bovids) – antelopes, buffaloes, cattle, sheep and goats, giraffes (Family Giraffidae), Deers (Family Cervidae), for example – which helps to explain why these animals dominate grasslands. The ruminant’s complex stomach acts like a fermentation tank, working to extract the maximum amount of nutrients from food. The animal assists in the process by regurgitating its food and chawing it a second time, making it even easier to break down. Non – ruminant plant eaters, such as zebras, have less efficient digestive systems and must therefore eat more to survive. In pure grassland, plant eaters – compete for the same food, although each may have a preference for a different type of grass. In savanna, the presence of trees and shrubs makes for a wide range of food, and browsing mammals have minimized competition further by evolving specific ways of feeding. This means that a remarkable number of species can live side by side. For example, the small Kirk’s dik-dik antelope feeds on shoots and fruit, and rarely touches grass, while the much larger land will eat almost anything from fruit and seeds to roots scraped up from the ground. Scavengers, which also play an important part in the habitat’s ecology, include birds as well as coyotes, jackals, and hyenas. Most air borne scavenges are vultures, but there are several species of stork, one of which, the Marabou stork, rivals the Andean condor for the title of the world’s largest flying animal.

• Deserts are places of extremes. Besides being dry, they experience intense sunshine, and a greater daily temperature range than any other land habitat. Rain – when it comes – typically falls in brief but torrential down pours, while strong winds pick up sand and grit, carrying it almost horizontally through the air. Although no two deserts are identical, true desert is usually defined as having less than 15 cm (16 in) a year – which typically falls during a relatively short spring or wet season followed by months of drought.

• TRUE DESERT

Most of the world’s true desert is found in two belts, one straddling each of the tropics. Here, zones of high atmospheric pressure persist for months at a time, preventing low – pressure air from bringing in rain. Desert also forms where mountains block – rain – bearing winds, and where cold coastal currents chill the air so that it carries very little moisture in land. In true desert, the amount of rain is so meagre, and so unpredictable, that very few plants can survive. The ones that do – such as CACTI and other succulents – are highly effective at collecting and conserving what little water nature provides: they have large networks of shallow roots, which drain the surrounding ground so thoroughly that, often, nothing else can grow nearby. For animals, this arid environment creates some interesting effects. With so few plants, there is very little soil, which severely limits invertebrate life. Most small animals such as insects, are found either on the plants themselves or in the debris that accumulates immediately beneath them. Larger animals, such as reptiles and rodents, venture away from these pockets of greenness, but even they have to be careful to avoid the worst of the daytime heat. Lack of vegetation means that most of the ground is exposed. Bare ground absorbs warmth very quickly when the sun rises, and re -radiates it once the sun has set. The dry air accentuates this effect, allowing daytime surface temperatures to soar to over 70°C (158°F). As a result, most animals living in true desert are active after dark. During the day they hide away leaving little sign of themselves apart from their tracks. TRUE DESERT occurs at mid – latitude in the northern and southern hemispheres, and it can have less than 5 cm (2 in) of rain a year.

• SEMI - DESERT

Compared with true desert, Semi - desert is more widespread, and it is also much more biologically productive. It is found in every continent, including some regions far outside the tropics. The modest but nevertheless reliable rainfall that Semi – desert receives has a dramatic effect on the landscape and the types of animal that it can support. Plants often grow in profusion, creating tangled thickets of vegetation that provide plenty of cover. There are woody species, which store most of their water in underground roots, and fresh succulents, which store it above ground in their stems and leaves. Most of these desert species are well protected from plant – eaters CACTI, for example, have extremely sharp spines, while SPURGES exude a poisonous milky sap when they are damaged – but, for animals that can overcome these defenses, they are an important source of food. Semi – desert also has plants known as desert ephemerals, which spring up rapidly after rain, flower, set seed, and them die. This short life cycle produces extra fresh food for animals and adds to the stock of seeds scattered over the desert floor. While some deserts are warm or hot throughout the year, others are surprisingly cold in winter. In the deserts of central Asia and in the northern parts of America’s Great Basin – the desert region between the Rocky Mountains and the coastal ranges further west – temperatures can fall to - 30° C (- 22°F). in these areas, animal need protection against winter cold as well as against summer heat; small animals, such as insects, usually become dormant in winter, and many burrowing mammals hibernate until the spring. Semi -  desert is most widespread in the world’s major landmasses, and it extends well into the temperate zone in both hemispheres. Compared to many other habitats in the world, desert has experienced relatively little human interference. Oil extraction can create environmental problems in deserts, but a more serious difficulty is caused by the exploitation of the habitat by livestock. Goats and other browsing animals can stunt or kill shrubs and other plants; and when these plants die, the sparse soil is often eroded, making it difficult for vegetation to recover. The result is desertification, or the spread of desert into areas where they did not previously exist. These newly created deserts are of little value to wildlife.

• LIFE IN DESERT

In a habitat where moisture is scarce, obtaining and conserving water are every animal’s top priorities. Desert animals practice a tight “water economy,” which means collecting water wherever they can, and minimizing water loss wherever possible. However; being economical with water is not in itself enough to guarantee survival; desert species have had to evolve various other adaptations to enable them to cope with a wide range of temperatures and the ever – present threat of food shortage. As a result, these animals are able to live in some of the driest places on earth.

• CONSERVING WATER

Most deserts have a scattering of OASES, where animals gather to drink. Some species need to drink daily, which restricts how far they can roam from an oasis. Others can survive on their on – board reserves for days or even weeks, depending on the temperature. A remarkable feature of desert life is that some animals can manage without drinking at all. Instead, they get all their water from their food. Some extract it from the moisture contained in food; but most use the food in manufacture metabolic water, which is created by chemical reactions when the energy in food is released. Seed – eating rodents are expert at this: although their food looks dry, they are able – to metabolize all the water they need. For drinkers and non - drinkers alike: water has to be eked out to make sure that it lasts. Compared with animals from other habitats, desert species lose very little moisture in their urine and droppings, and only a small amount is released from their skin and in their breath. Desert species are also good at withstanding dehydration. The dromedary or one – humped camel, can lose nearly one half of its body water and survive. For humans, losing just a fifth can be fatal.

• STORING FOOD

To enable them to cope with erratic food supplies, many animals keep their own – food stores. Some do this by hiding food away. The North American Kangaroo rat, for example, constructs underground granaries that contain up to 5 kg (11Ib) of seeds. But for predators, and for animals that browse on shrubs, creating such larders is not possible. Their food is difficult to collect and to transport, and even if it could be hoarded, it would be unlikely to remain usable to more than just a few days. The answer is to store food inside the body. The classic example of this is the Camel, which stores surplus food, in the form of fat, in its hump. Several other species, such as the Gila Monster and Fat – Tailed Dunnart, store food in their tails.

• COPING WITH HEAT AND COLD

In desert, the temperature rarely stays steady for more than a few hours, and it can reach extremes of both heat and cold very quickly. Humans lose excess heat by sweating, but at very high temperatures this cooling system can use as much as 1 liter (35 fl.) of water an hour – far more than any desert animal could afford. Desert animals tackle the heat problem in two ways; by reducing the heat they absorb, and by increasing the heat they give out. Light – colored skin or fur reflects some of the Sun’s rays, minimizing heat absorption; but a much more effective method – used by many desert animals – is to avoid the most intense heat by being nocturnal (active by night), spending the day sheltering underground. Burrows do not have to be very deep to make a difference: while the desert surface maybe too hot to touch, the ground just a few centimeters below it will be relatively cool. Getting rid of excess heat is more difficult, particularly when an animal’s body temperature is dangerously high. Lizards and snakes are often described as “cold blooded”, but this actually means that their body temperature rises and falls with that of their surroundings. Although they thrive in warm habitats, and can survive with a body temperature of up to 44°C (111°F), they often have to sit out the hottest part of the day in shade. Some desert birds cool down by panting, which involves fluttering the flap of skin over their throats. Desert Kangaroos and wallabies lick their front legs, covering them with saliva. As the saliva evaporates, the animal’s blood cools down. In high – latitude desert regions, such as the Gobi Desert of Central Asia and the Great Basin Desert of North America, winter can be extremely cold. Animals have various ways of coping with this. Most reptiles hibernate, while birds often fly to warmer climates. Mammals keep warm by growing thick fur, or by sheltering underground.

• EXPLOSIVE BREEDING

Desert animals often have high, variable breeding seasons. Instead of reproducing at a fixed time of year, many produce young when there is the best chance of finding food. Female Kangaroos, for example, give birth extremely regularly when food is plentiful, but when food is scarce they stop breeding altogether. This flexible system is an efficient way of using resources because it prevents parents having to tend hungry youngsters when they are hungry themselves. Some desert species carry irregular breeding to extremes. Desert wildlife includes a number of animals that, paradoxically, live or breed in water and, for those species, reproducing is a highly unpredictable and time sensitive business. Such animals include burrowing frogs and toads, and also freshwater shrimp that live in temporary pools. For months or even years at a time, they are invisible part of desert wildlife; with the amphibian species lying hidden underground, and the shrimps present only as eggs in dried – up ground. But immediately after a heavy storm, the frogs and toads dig their way in the surface, and the shrimp eggs hatch. Once active, these animals immediately set about finding mates because they have to complete their life cycles before the pools dry up again.

• MOVEMENT

Desert sand makes life difficult for animals on the move. Larger animals sink into it, while small ones struggle to climb up and down slopes of shifting grains. To combat the problem, some animals, such as golden and marsupial moles, move through the sand rather than above it. Others, such as camels and geckos, have extra-large feet, which help to spread their body weight over the surface of the sand and so increase stability. Side winding snakes have a different solution: they throw themselves forwards in a succession of sideways jumps, leaving a characteristic pattern of J – shaped tracks. In addition to saving energy, this method helps to minimize contact with hot ground. Some insects and lizards have learnt to tolerate hot ground by alternating the feet that are in contact with the ground at any one time. Having long legs also helps as they hold the animal’s body away from the sand’s surface, where the heat is fiercest.

• NOMADIC ANIMALS

Where food and water supply is patchy, some animals adopt a wandering lifestyle. This is common in desert habitats, especially in animals that can fly. Desert locusts are famous for their huge nomadic swarms, and some desert birds, particularly seed – eaters, form large nomadic flocks. Unlike migrants, nomadic animals do not follow fixed routes – the weather often dictates their course – and they breed erratically, wherever they find a good food supply.

• Forests have flourished in the tropics for longer than they have existed anywhere else on earth, which helps to explain why the animal species that live there outnumber those of all other land habitats combined. Most large tropical forest animals have been identified and classified, but the invertebrate life is so diverse that the task of cataloguing it will never be complete. There are two (2) main types of tropical forest: rainforest, which is closest to the equator; and seasonal or monsoon forest, which grows towards the edges of the tropical belt.

• TROPICAL RAINFOREST

Near the equator, the climate is warm and moist all year round, creating ideal conditions for plant growth. As a result, trees and other forest plants grow almost incessantly in an endless competition for light. Some plants put all their resource into growing towering trunks, while others are adapted for survival in partial shade. As a result of these different growth patterns; the forest is divided into clearly defined layers, each with its own characteristic animal species. The highest layer; at about 75m (245 ft.), consists of giant, isolated trees called EMERGENTS. These provide nest sites for predatory birds and feeding platforms for monkeys. Beneath this level is the CANOPY, where copious light, combined with some protection provided by the EMERGENTS, results in a continuous layer of branches and lush foliage up to 20m (65 ft.) deep. This layer feeds or harbors most of the forest’s animal life. Below the CANOPY is the UNDERSTOREY – a more open layer made up of shade – tolerant trees. On the forest floor: leaf litter is food for some very small animals as well as support for plants and saplings that grow where sufficient light filters through from above. This zonal pattern is characteristic of lowland rainforest (the most common rainforest type). At higher altitudes, the trees are lower and the layers are more compressed – an effect that is exacerbated as altitude increases until eventually the trees form ELFIN FORESTS little more than head high. Soil is also an important factor in shaping the forest. In some parts of the tropics, such as the Rio Negro region of South America, infertile sand results in the growth of stunted trees with leathery leaves. TROPICAL RAINFOREST is found near the equator, when annual rainfall exceeds 2.5 m (8 ¼ ft.) and is evenly spread throughout the year.

• SEASONAL (MONSOON) FOREST

Unlike rainforest, where the climate is very stable, seasonal forest grows where rainfall is concentrated into a wet, or rainy, season, which is known as Monsoon. Up to 2.5 m (8 ¼ ft) of rain can fall in just three months – as much as some tropical rainforests receive throughout the whole year. As a consequence, seasonal forest is not as tall as tropical rainforest and, typically, the canopy is more open and extends further towards the forest floor. Immediately after the monsoon, seasonal forest is lush and green; but in the long dry season that follows, many of the trees shed their leaves, and the piercing sunlight is able to reach through the bare branches to the ground. Some seasonal forest trees are unusual in that they flower and fruit after losing their leaves. When this happens, birds, insects, and mammals congregate in large numbers to feed. In the rainy season, the forest’s animals are well hidden by the foliage; once the leaves have fallen, they become much easier to find. Despite the yearly cycle of deluge and drought, the animal life of seasonal forest is some of the most numerous and varied in the world. In the southern Asia, which has the largest area of this type of forest, the habitat supports elephants, monkeys, leopards, and also tigers. In Asia’s seasonal forests there are some spectacular birds, including giant hornbills, and some of the world’s largest snakes. In Africa, seasonal forest abounds with browsing antelopes, while, in central America, they are inhabited by Pumas, coatis, and white – tailed deer. Most of these animals breed during the wet season, when they can take advantage of the abundant supply of fresh leaves. SEASONAL FOREST grows on either side of the equator. The dry season lasts longer the further the region is from the equator.

• LIFE IN TROPICAL FOREST

Some tropical forest animals spend all their time on the ground. For most, however, daily life involves getting about among trees. The canopy holds most of the forest’s food, so an animal that is good at moving around in the treetops has the greatest chance of thriving. Some animals are so well adapted to life in the trees - breeding as well as feeding there that - they very rarely have to visit the forest floor.

• MOVING IN TREES        

Small animals need relatively few special adaptations for moving about in trees. Ants, for example, are so light that it makes little difference to them whether they are travelling up and down trees or across the forest floor. But for larger animals, such as apes, monkeys, and other primates, climbing is a dangerous occupation: if they lose their grip – as occasionally happens – they risk a fatal fall. Most primates climb by running or leaping along the tops of branches, often using familiar routes that act like highways through the trees. Monkeys follow these routes mainly by sight, but many of the more primitive primates, such as bush babies, move about after dark, identifying their pathways partly by small. Gibbons are different again: they travel underneath the branches by swinging hand – over – hand in a breathtakingly acrobatic manner. This unusual but highly effective form of movement is called BRANCHIATION. Tropical forest harbors a huge variety of flying animals – birds, bats, and flying insects – that swoop or hover among the treetops. However, during the course of evolution, many unrelated animals, including mammals, frogs, and even snakes, have developed wing – like flaps of skin that enable them to glide. Some of these gliders can travel over 100m (330 ft) from tree to tree and, remarkably, many of them are most active at dark.

• COMMUNICATION

In any Kind of forest, animals face problems keeping in touch. In the Canopy, leaves and branches make it difficult to see for more than a few meters, while tree trunks get in the way on the ground. As a result, many forest animals rely on sound and scent, rather than visual signals, to claim territories and attract partners. Some of the loudest animals in the world live in tropical forests. They include howler monkeys, bellbirds, parrots, cicadas, and an enormous variety of tree frogs. Like mammals and birds, each species of tree frog has its own characteristic call: some produce a short metallic “tink”, others generate a sustained trilling that sounds like machinery. Signaling with sound can be dangerous because it can attract predators as well as potential mates. Tree frogs and cicadas minimize the problem by pitching their calls so that the source is very difficult to locate. Other animals – including many mammals and flying insects, avoid the problem by using scent to stay in touch. One great advantage of scent is that it lingers: for example, in marking its territory, a jaguar or okapi leaves a signal that will last for several days.

• KEEPING OUT OF DANGER

Tropical forest abounds with camouflaged animals as well as species that mimic others. Animals that use camouflage – chiefly insects and spiders, but also snakes, lizards, frogs and toads – resemble a huge variety of in animate objects, from bark, thorns, and bird droppings to branches and fallen leaves. Many animals use Camouflage to avoid being spotted and eaten, but some predators also use it to enable them to ambush their prey. Mimicry, in which one species “pretends” to be another, is a subtler means of avoiding attack. It involves a relatively harmless species evolving to look like one that is dangerous, and it is most common in invertebrates. Some tropical forest spiders, for example, closely resemble stinging ants and even move like them as well. Matters are complicated where several species come to look alike. Some groups of unrelated butterflies, which contain poisons that are distasteful to birds, imitate each other; thus they have evolved the insect equivalent of a shared warning trademark. Warning signals are most developed in extremely toxic animals. For example, unlike other frogs, tiny poison – arrow frogs hop nonchalantly about the forest floor, relying on their extraordinarily vivid colors to warm other animals that they are not merely unpalatable but highly dangerous to eat.

• FEEDING

Near the equator, trees grow, flower, and set seed all year round, generating a non – stop supply of food. Many forest animals – including bats, birds, and insects – live almost exclusively on the abundant nectar and fruit. Some of these animals help trees to spread their pollen and seeds. Quetzals, for example, swallow fruit whole: and then regurgitate the stones onto the forest floor where they can germinate. Compared with flowers and fruit, tropical forest leaves are difficult to digest. Animals that feed in these leaves generally pick them while they are still young – before protective toxins have had a chance to build up inside them. Insects are the most prolific leaf – eaters, but some of the forest’s larger animals also rely on this difficult diet. They include several kinds of monkeys and sloths, and the HOATZIN – a highly unusual bird from South America. The HOATZIN processes its food much as a grazing mammal does after eating, it is often so heavy that it can barely fly. Tropical forest predators range from some of the world’s smallest insects to the largest cats. In an environment that provides lots of cover, most of them stalk their prey rather than running it down. Army and driver ants are the most remarkable exceptions: they hunt in “packs” over 50,000 strong, over powering and eating anything that cannot escape.

• REPRODUCTION

For animals that live in trees, breeding can sometimes involve unusual adaptations. Some tree frogs come down to the forest floor to lay their eggs, but many lay them high up in the canopy, either in water – filled tree holes or in the pools of water that gather in plants. Some frog species are more creative, laying their eggs in nests of foam that keep their eggs moist until the tadpoles are ready to hatch. Many tropical birds start life in the safety of tree – holes, but climbing – mammals rarely build nests, and many of their young start life in the open. Young monkeys often climb to their mothers’ chests, keeping a tight grip as the parent runs along branches or leaps through the air. For young murine (mouse – like) opossums, which live in the American tropics, early life is even more precarious because their mothers do not have well – developed pouches. This means that until their feet have developed the ability to cling, these tiny marsupials hang from their mothers’ teats by their mouths, their legs dangling in the air.

• Temperate forest grows in regions that have a wide range of climates. In some, winters are cold and summers are cool; in others, the winter is relatively mild, and the summer heat rivals that in the tropics. Where winters are cold, temperate forest trees are usually deciduous, shedding their leaves in winter and growing a new set in spring; in warmer regions, many trees keep their leaves all year. Although temperate forest does not have as many animal species as tropical forest, it is still among the richest wildlife habitats on land.

• DECIDUOUS FOREST

In the depths of winter, deciduous forest can seem gaunt and empty and largely devoid of animal life. But as the days lengthen in spring, and buds begin to burst, the habitat becomes alive with birdsong and animals on the move. This transformation is triggered by a sudden abundance of plant food - one that nourishes large numbers of plant – eating insects as well as the animals that feed on them. Many of these forest animals are permanent residents, but they also include migratory birds that fly in from distant parts of the world. Compared with tropical forest, temperate deciduous forest has relatively few tree species: the maximum number – found in some of the forests of eastern North America – is several hundred, while tropical forest might contain several thousand. Never the less, temperate forest trees are power houses of life. Large oak trees, for example, can produce over a quarter of million leaves a year – enough to sustain the army of weevils, gall wasps, and moth caterpillars that feed rapidly in spring and early summer while the leaf crop is at its freshest and most nutritious. Like tropical forest, deciduous forest has a clear vertically layered structure, but there are some important differences. The trees are rarely more than 30m (100ft) tall, and the canopy layer is usually deep but open, allowing light to reach the understory and encouraging plant growth. Fallen leaves rot slowly in cool conditions, so deciduous forest has an unusually deep layer of leaf liner that insects, woodlice, and millipedes use as food and cover. This means that while many small animals live in the cracks and crevices in bark, the place that is richest in invertebrate life is not the trees but the ground. Large areas of temperate deciduous forest are found in northern hemisphere; most temperate forest in the southern hemisphere is ever green.

• EVERGREEN FOREST

In warm parts of the temperate world, many broad leaved trees are evergreen. Unlike trees of deciduous forest, which grow in spring and summer, evergreens grow in winter and spring, when temperatures are low but not cold, and when water is readily available. Described by botanists as SCLEROPHYLLOUS (meaning hard - leaved) forest, this habitat is found in several widely scattered regions of the world, including parts of California and western south America, the Mediterranean region in Europe, and large areas of eastern and south western Australia. In some of these places the forest is low – growing, but in Australia, where eucalyptus is the dominant species, it includes the tallest broadleaved trees in the world. Temperate evergreen trees usually have open crowns, which means that the vertical layers are usually less pronounced than they are in forests in cooler regions, and plenty of light is able to reach the forest floor. As a result, these forests are rich in ground – based wildlife, and warmth - loving animals such as lizards and butterflies, which are usually associated with higher levels -  can often be seen sunbathing on the floor. The open structure also makes it easy for birds, such as Kookaburras and other forest Kingfishers, rollers and hoopoes, to swoop down on animals moving about on the ground. The air in evergreen forest often smells pleasantly aromatic because most of the leaves are filled with pungent oils. These oils help to stop the leaves from drying out, and they also protect them from animals. They are a highly effective deterrent, for relatively few animals – apart from specialists such as the koala – include these leaves in their diet.  TEMPERATE EVERGREEN FOREST is found in regions with a Mediterranean – type climate; mild, damp winters, and warm, dry summers.

• LIFE IN TEMPERATE FOREST         

The factor that most affects life in temperate forest is the variable food supply. At all levels – from the treetops to the forest – floor - the life cycles of forest animals living in temperate forest move in step with the seasons so that they produce their young when food is easiest to find. Life is relatively easy in spring and summer; but in winter, when the food supply is at its lowest, special adaptations are needed for survival.

• FEEDING

As a habitat, deciduous temperate forest – the Kind of forest found across much of the northern hemisphere – has one very useful feature. The trees that grow in it, such as OAKS and BEECHES, produce leaves that are designed to last for just one growing season. As a result, these leaves are usually thin and easy to eat, which is why vast numbers of insects feast on them from the moment they begin to appear in spring. This sudden explosion of insect life attracts an army of highly specialized avian predators. In Europe, northern Asia, and North America, dozens of Warbler species migrate north as the buds open. These birds have extremely acute eyesight, enabling them to scour leaves for the tiniest grubs and caterpillars, which they then pick up with their tweezer – like beaks. Other birds, including tree creepers, woodpeckers, and nuthatches, concentrate on the bark, seeking out and pecking at the tiny animals hidden among the crevices.  By midsummer; leaves stop growing, and animal feeding behavior changes. Most temperate trees are pollinated by wind, which means that they do not produce enticing nectar – rich flowers. However, they do produce large crops of nuts and other seeds, which are extremely important foods for animals because, unlike leaves, they can be stored away and used when other food is scarce. Food storage, “or “catching”, is practiced by many forest birds and Mammals. Jays bury acorns in the ground, while acorn woodpeckers store them in trees. Squirrels bury seeds of all kinds, and red foxes bury anything that is even faintly edible, from half – eaten remains to food wrappers and discarded shoes. Some animals locate their stores by scent, but most are very good at pin pointing them by memory alone; finding and digging up their food even when it is covered by snow. Seed – catching has an important impact on forest ecology. Although animals that burry seeds have good memories, some of what they hide is always forgotten about. This means that provided the seeds are not discovered by rodents or other animals, they remain effectively planted and ready to germinate, helping the forest’s trees to reproduce.

• HIBERNATION

In autumn, many insect – eating birds migrate to warmer climes, leaving the forest’s remaining animals to face the winter cold. Animals that store food can remain active throughout this difficult time of year, but others use a very different survival strategy: they hibernate, living on the fat reserves they have built up during the summer months. How long and how deeply an animal hibernates depends on where it lives. In the forests of northwest Europe, hedgehogs may hibernate for up to six months, whereas further south their winter sleep is much shorter. In eastern North America, woodchucks or groundhogs – typically hibernate from October to February; their wanderings early in the year are a traditional sign that spring is not far off. Some hibernating animals, such as the common dormouse, hardly ever interrupt their winter break, even if they are picked up. However, many hibernators behave in a different way. If the weather turns warm, they briefly rouse themselves; bats, for example, take to the air for feeding flights, while hedgehogs often move out of one hibernation nest and into another. But forest hibernators have to be careful not to do this too often; activity uses up their bodily food reserves, and it therefore puts them at risk of running out before the winter is truly over. Many insects also hibernate, often hidden under bark, but, in some species, the adults die out, leaving behind tough, over wintering eggs that will hatch in spring.

• MOVEMENT

While monkeys and gibbons are the most impressive climbers in tropical forest, Squirrels are the experts in temperate forests. Unlike many climbing mammals, they can run head – first down tree trunks, as well as up them, by hooking their long, curved hind claws into bark. Squirrels have excellent eyesight, and they instinctively scuttle to the back of a tree if they spot a potential predator – a simple behavior that makes them difficult to catch. Temperate forest is inhabited by gliding rodents, and also – in Australasia by gliding marsupials. But for precise maneuvering among trees, owls and birds of prey (Raptors) are unrivalled. Unlike their relatives in open habitats, most of these aerial hunters have relatively short, broad wings that enable them to twist and turn effectively. A prime example of this adaptation to woodland life is the Eurasian sparrow: rather than soaring and then swooping, it speeds among trees and along hedgerows – sometimes only a meter or so above ground – ambushing small birds in mid – air and carrying them away in its talons. Temperate forest provides ground dwelling animals with lots of cover. As a result, small mammals, such as voles and shrews, abound on the forest floor. To avoid being seen as they move about, these animals often use runways partly covered by grass or fallen leaves. Voles use a combination of vision, smell, and touch to find their way along these runs, but shrews which have very poor eyesight, navigate partly by emitting high – pitched pulses of sound.  These signals bounce back from nearby objects in the same way as those sent out by a bat’s sonar system.

• LIVING IN LEAF LITTER     

The leaf litter in temperate forest is one of the world’s richest animal micro – habitats. This deep layer of decomposing matter harbors vertebrates, including mammals and salamanders, but its principal inhabitants are invertebrates that feed on leaf fragments, on fungi and bacteria, or on each other. Some of these animals – such as centipedes and woodlice – are large enough to be easily seen, but many others are microscopic. Animals that live deep in leaf litter exist in total darkness, so most of them rely on their sense of touch to find food. This is especially true of predators: centipedes locate their prey with long antennae, while tiny pseudo scorpion use the sensory hairs that cover their pincers. Like true scorpions, pseudo scorpions are venomous: but they are so small that they pose no threat to anything much bigger than themselves. This is fortunate because in just a few square meters of leaf litter their numbers can run into millions. Dead leaves are a useful screen, hiding leaf litter dwellers from other animals foraging on the forest floor. However, it is not totally secure. Some temperate forest birds, particularly thrushes, pick up leaves and toss them aside, snapping up leaf litter animals as they try to rush away from   the light.

• CONIFERS are the world’s toughest trees. Their small, needle – shaped leaves can withstand extreme cold and are impervious to strong sunshine and wind, and their relatively narrow, upright habit enables them to grow closely together to form dense, sheltered forest. As a result, CONIFERS thrive where few broadleaved trees can survive, such as the far north and in mountain ranges. They also flourish in places that have very heavy rainfall. In such areas they form temperate rainforest, home to some of the largest trees in the world.

• BOREAL FOREST

Boreal forest named after BOREAS, the ancient Greek god of the north Wind, boreal forest, or taiga, is the largest continuous expanse of forest on earth. It covers about 15 million square km (6 million square miles) and stretches in an almost unbroken belt across the far north, often reaching deep into the ARCTIC.  In some places, the belt is over 1,600 km (1,000 miles) wide. Across the boreal forest belt as a whole, winter temperatures routinely drop below - 25°C (- 13 °F) but in some of the coldest regions, such as northeast SIBERIA, temperatures can fall below - 45°C (- 49°F). Summers in boreal forest are brief but can be warm. Compared with the types of forest that occur at lower latitudes, boreal forest has only a handful of tree species and therefore provides only a limited variety of food for herbivores. Plant diversity is also restricted both by the amount of light that can reach the FOREST FLOOR and by the high acidity of pine needles. Even in summer the interior of the forest is often dark, with a thick layer of dead needles carpeting the floor. FUNGI thrive in these conditions, but the only forest – floor plants that live here are the ones that can tolerate low light levels and acidic soil conditions. Apart from insects, few animals can digest CONIFER LEAVES or wood, so most plant – eaters concentrate on SEEDS, BUDS, and BARK; or on berries from low – growing shrubs. However, what the habitat lacks in variety, it more than makes up for in quantity, especially as there is relatively little competition for food. This is one of the reasons why many boreal forest animals from birds to bears have far more extensive ranges than species that live in warmer parts of the world. BOREAL FOREST stretches across much of the far north. There is no equivalent habitat in the southern hemisphere.

• TEMPERATE RAINFOREST      

The world’s largest areas of rainforest are found in the tropics, but rainforest also exists in parts of the TEMPERATE WORLD. It grows where west – facing mountains intercept moist air blowing in from the sea and, unlike BOREAL FOREST, it experiences relatively mild temperatures all year round. Compared with BOREAL FOREST, temperate rainforest is a rare habitat, occurring in a few widely separated areas. In the southern hemisphere, it is found in the South Island of New Zealand, and in parts of southern Chile. In both of these places, most rainforest trees are BROAD LEAVED SPECIES, but in America’s Pacific northwest – where the largest temperate rainforest in the world can be found – the trees are almost entirely COMFERS. Some are over 75m (nearly 250 ft) high, and more than 500 years old. This kind of Coniferous forest looks unlike any other. On the ground, and in the understorey, every surface is draped with ferns or water logged moss. Densely packed trunks, some over 3 m (9 ¼ ft.) across, rise up to the CANOPY high overhead, where the sky is always laden with rain. Temperate rainforest supports many animals that are found in coniferous forest all over the world, but it has some additional features that set it apart: the mild, damp conditions, which make it a haven for SLUGS and SALAMANDERS, and the immense amount of fallen timber, which creates opportunities for insects that feed on dead wood. In its natural state, the forest teems with mammals, as well as with owls and other birds that need large, old trees as nest sites. Unfortunately, these trees are in great demand by the timber industry and, as a result, untouched temperate rainforest is increasingly rare. TEMPERATE RAINFOREST is found on well – facing coast, where heavy rain falls throughout much of the year.

• LIFE IN CONIFEROUS FOREST

For animals and trees alike, life in boreal forest is dominated by the need to survive long and extremely cold winters. Animals that remain active in winter, such as wolves, need a constant supply of food simply to avoid freezing. CONIFERS are difficult to exploit for food, which means that animals that rely on them have developed some highly specialized physical and behavioral characteristics.

• FEEDING  

Compared with many broad leaved trees, CONIFERS are well protected against attack. In addition to tough leaves, they often have oily resins that made both their leaves and their wood difficult to digest. Furthermore, if the sapwood is injured, this resin oozes out and traps insects and spiders as effectively as glue. Despite these defenses, some animals manage to live entirely on coniferous trees. Among the most successful are sawfly larvae. These caterpillar – like grubs bore deep inside the trunks, leaving cylindrical tunnels in the wood. They do not eat the wood itself: instead they feed on a FUNGUS that grows on the walls of the tunnels they have built. Female sawflies carry small amounts of this fungus with them when they emerge as adults, and they infect new trees when they lay their eggs. This kind of symbiotic partnership is vital to sawflies, but it is not entirely unique; in other habitats, particularly in the tropics, ants and termites also “cultivate” fungi as food. Although wood – boring grubs are safe from most predators, they are not entirely immune from attack. Coniferous forest is the habitat of some of the world’s largest woodpeckers, which hammer their way into tree trunks to reach the GRUBS inside. Sawflies also face a threat from the ichneumon wasp, which drills through the wood with its long ovipositor to lay its eggs on the sawfly larvae. It is thought that the WASP locates the larvae by smell. When the eggs hatch, the ichneumon grubs eat their host larvae alive. Some animals, such as the Capercaillie and North American Porcupine, eat large quantities of conifer needles, but moth caterpillars are the leading leaf – eaters: as always in coniferous forest, the number of species involved is small, but the damage they inflict can be vast. This is especially true of species such as the gypsy moth, which has been accidentally introduced to many parts of the world.

• FINDING WINTER FOOD

CONIFERS do not have true flowers, but they never the less produce seeds. For birds and small mammals, this seed crop is a valuable winter fuel. However, accessing conifer seeds is not easy: they develop inside woody cones, and the cones stay tightly closed until the seeds inside are mature. Coniferous forest animals have developed a variety of ways of removing these seeds before the trees scatter them on the forest floor. Squirrels gnaw through the soft, unripe cone while it is still attached to the branch, eating the seeds and dropping the remains of the cone on the ground below.  Woodpeckers often take fallen cones and wedge them into tree – holes or broken stumps, using these to hold the cone firm while they peck out all the seeds. Crossbills are even more proficient: Their beaks are uniquely adapted for dealing with cones, enabling them to extract the seeds with surgical precision. Compared with seeds, bark is a low – quality food, but in winter it is vital to some species’ survival. Deer strip it away from the base of young saplings, while bank voles and porcupines often climb trees to attack the bark higher up. Bark stripping often stunts a tree’s growth, and a severe attack can kill it.

• COPING WITH COLD

CONIFERS FOREST has its share of seasonal visitors, principally insect – eating birds that arrive in spring and then leave for the south once they have raised their young. But for the rest of its animals, long winters are an inescapable fact of forest life. Some species hibernate, but many remain active even during the coldest months, relying on their insulation for survival. One group of forest animals, the mustelids, have coats that are exceptionally well insulating. This group includes PINE MARTENS, WOLVERINES, MINKS, and SABLES, all of them agile hunters renowned for their thick and luxurious fur. As with most mammals, their coats contain two different kinds of hair: long, outer guard hairs form the coat’s water – repellent surface, with shorter, much denser hairs – the underfur – trap a layer of air close to the body, keeping the animal warm. Northern species all grow an extra - thick coat after their late summer – molt; and some species, such as the STOAT, use this molt to change color, developing a white coat that provides better camouflage for the winter. Keeping warm is relatively easy for large mammals because their bodies contain a large store of heat. But for the smallest warm – blooded inhabitants of coniferous forest, winter conditions test their cold tolerance to its limits. Voles and other rodents can hide in burrows, but birds spend most of their lives in the open. For wrens and tits, which often weigh less than 10g (3/8 02), winter nights are a particularly dangerous time. With such minute bodies, their fuel reserves are tiny, and so they must make species provision if they are to stay alive until dawn when the search for food can resume. Some of them make the most what body heat they have by huddling together in tree – holes, but a few, such as the SIBERIAN TIT, bed down in the snow, using it as an insulating material.

• POPULATION CYCLES

Since there are relatively few animal species in the northern coniferous forests, the lives of predators and prey are very closely linked. During mild years, strong tree growth can trigger a population explosion among small animals; as a result, the predators that feed on them begin to increase in number. These conditions never last for long, though; as the plant – eaters begin to outstrip the food supply, their numbers start to fall again. And as the rate of the fall accelerates, the predators soon follow suit. Despite the unpredictability of the northern climate, these ups and downs occur with surprising regularity. In North America, fur trappers’ records dating back over a century provide some long term evidence of population swings. For example, they show that the SNOWSHOE HARE population roughly follows a 10 – year cycle, with two, or three good years, followed by a lengthy slump. The Canadian Lynx – one of the snowshoe hares’ main predators – follows the same pattern, but with a one – or two-year time lag. Similar cycles involving lemmings and other small mammals take place in TUNDRA. While there is little that they can do to prevent this boom – and bust pattern from occurring, animals like the snow shoe hare are able to make a fairly fast recovery from a population slump by breeding quickly when conditions are favorable.

• IRRUPTIONS                                              

In the northern coniferous forests, food supplies are affected by the weather and the degree of competition. In winters that follow cool summers, the supply of seeds and berries can be thin, leaving seed – and fruit – eating birds with little to survive on. Rather than starve, these birds fly south in waves, called IRRUPTIONS, which may involve travelling beyond their normal winter range by as much as 1,500 km (930 miles). Species that frequently irrupt include crossbills, waxwings, and tits, as well as nutcrackers and other seed – eating members of the crow family.

• In many land habitats, climatic conditions vary only slightly within a region. In mountains, however, the average air temperature drops by about 1°C (1.8°F) for every 200 m (650 ft.) gained in height, oxygen becomes scarcer, and the air becomes less effective at screening out ULTRAVIOLET LIGHT. As a result, mountains can be divided into distinct zones, each supporting plant and animal life that is very different from that of the zone above and below. A wide range of animals live in the low – altitude foothills, but only the hardiest survive year round in the harsh environment above the TREE LINE.

• TEMPERATE MOUNTAINS

In temperate regions, a mountain’s climate is relatively COOL throughout the year. However, seasonal changes are much more marked than they are in the tropics. At high altitude, above the tree – line, there is a sudden burst of plant growth in spring and summer. Some animals migrate upwards to make use of this brief abundance of food, but others, such as the MARMOT, are permanent residents between mid – and high altitude, surviving the winter cold by living in burrows, and by hibernating for up to eight months in a dormant state, coming to life. When WARM WEATHER arrives. For many, this dormant period is spent inside the eggs, which hatches when the days lengthen and the temperatures rise. At lower altitudes, the climate is warmer, and generally more like that of the surrounding land. However, because the sloping, rocky ground is difficult to farm, the mountain sides often retain more of their TREE COVER than does flatter ground. In undisturbed conditions, these MONTANE FORESTS are the natural habitat of large mammals, such as MOUNTAIN LIONS, BEARS, and DEER, and also of a wide range of seed – and insect – eating birds. Temperate mountains abound in birds of prey (Raptors). Some such as PEREGRINE FALCON, pursue their prey on fast – flapping wings, while EAGLES and BUZZARDS soar high up, riding on up draughts. One characteristic mountain species, a vulture called LAMMERGEIR, turns the mountain landscape to its advantage by carrying CARRION BONES aloft and dropping them onto the rocks to expose the edible marrow inside. THE NORTHERN TEMPERATE ZONE’S MOUNTAIN RANGES include the highest peaks on earth. In the southern hemisphere, mountains are smaller and more isolated.

• TROPICAL MOUNTAINS   

 In the tropics, the generally warm climate means that Mountain vegetation zones extend much higher than they do in Montane habitats elsewhere in the world. For example, near the equator, trees often grow at altitudes of up to 4,000 m (13,200 ft.), which is why many tropical mountains are forested to their summits. Above this altitude is the tropical alpine zone, an open landscape dominated by grass and some highly specialized plants. This zone is often above the clouds, which means that nights are cold and frosty and yet the sunshine is fierce. Many tropical animals have successfully adapted to life at high altitude. They include the vicuna, which can be found up to 5500 m (18,100 ft.) in the south American Andes, and the YAK, which reaches a record 6000 m (19,800 ft.) just north of the tropics in the HIMALAYAS. Birds also live at great heights: in south America, for example, mountain hummingbirds called ANDEAN HILL STARS often feed at over 4,000 m (13,200 ft.). The Andean hill star’s minute size means it has difficulty in storing enough energy to enable it to survive the cold nights. To combat the problem, its nocturnal heart beat slows down and its temperature plummets, conserving energy. The cloud – covered forest below the ALPINE ZONE is the habitat of some of the world’s most endangered animals. They include the eastern gorilla – a species restricted to the mountains of Central Africa – and the resplendent quetzal, a bird that lives in the cloud forests of central America. The abundant moisture means that the FOREST ZONE also teems with many different species of grog, living both on the ground and in trees.  

• LIFE IN MOUNTAINS  

Life at high altitudes can be HARSH. Food is often scarce, the weather can be treacherous, and the thin air can make it difficult to breathe. However, there is also more space, relatively little interference from humans, and fewer predators than there are lower down. Many animals are “incomers”, using high ground as an extension of their normal range, but there are also some that live only on high ground. In large mountain chains, many animals have a wide distribution: but isolated peaks are often in habited by animals that are found nowhere else.

• BREATHING THIN AIR

At 6,000 m (19,800 ft.), air is half as dense as it is at SEALEVEL. As a result, it contains only half the normal amount of oxygen – so little that anyone trying to breathe at this height would have difficulty remaining conscious. Yet some mountain animals live even higher than this because they have evolved specialized body systems that enable them to get the maximum amount of oxygen into their blood. In the vertebrate world, birds are the unrivalled experts at high – altitude living. This is because air passes through their lungs in only one direction, not in and out, which ensures that a high proportion of the air’s oxygen enters the blood – far more than enters a mammal’s blood stream in the same conditions. This fact is apparent from the height at which birds are capable of flying. In the Himalayas, Choughs have been seen fluttering around campsites at over 8,000 m (26,400 ft.), and there are records of vultures colliding with planes at over 11,000 m (36,300 ft.) – far higher than mount Everest. Birds are unusual in being able to cope with rapid changes in altitude without experiencing any ill effects. For mammals, moving from one altitude to another necessitates special adjustment by the body; which is achieved by ACCLIMATIZATION – a process that can take several weeks to complete. During ACCLIMATIZATION, the number of red cells in the blood slowly increases, boosting its oxygen – carrying capacity. This physical adjustment, which is shown by a broad range of mammals including HUMANS is temporary. If an animal moves back to lower ground, the process is reversed. However, for mountain mammals, such as the VICUNA and IBEX, adaptation to life high up is a permanent state, not something that can be switched on and off. When measured as a proportion of volume, VICUNAS have three (3) times more red cells in their blood than most other animals, and the HAEMOGLOBIN in their red cells is unusually good at collecting oxygen. As a result, VICUNAS can run almost effortlessly on the ALTIPLANO – the high – altitude plateau that runs the length of the ANDES. Compared with mammals, cold – blooded animals such as reptiles, have fewer problems with thin air because they use oxygen more slowly. For them, the main problem with mountain life is COLD: if the temperature is too low, their body processes slow down, and their muscles have difficulty working.

• MOVEMENT

Mountains seem almost purpose made for soaring birds because strong air currents make it easy for them to gain height. For animals on or near the ground, moving about is not so easy. Many insects are wingless, and species that do fly usually keep close to the rock to reduce the risk of being blown away by the wind. For larger animals, the situation is even more hazardous, for a single misjudged move can lead to a fatal fall. Many – rock – dwelling mammals therefore have feet designed to prevent slipping. In Australia, rock wallabies use their large back feet to take leaps of up to 4m (13 ft.), with their long tails helping them to balance. In Africa and the middle East, hyraxes run over rocks and boulders with the help of specialized soles, which work like suction cups. But in most of the world’s mountains, the most adept climbers are hoofed mammals. Hooves may seem far from ideal for climbing, and it is true that some hoofed mammals, such as HORSES, have great difficulty moving about on rocky slopes. But in climbing mammals, such as MOUNTAIN GOATS and KLIPSRINGERS, hooves have evolved into perfect aids for moving about in mountains: they are small and compact, allowing them to fit onto narrow ledges, and they have hard edges surrounding rough non – slip pads. These combined characteristics make for good grip in all conditions, including rain and snow. Getting a firm grip is essential for moving on rock, but equally important is a strong sense of balance and head for heights. Most terrestrial mammals are instinctively afraid of steep drops, but from an early age, mountain dwellers show what appears to be a reckless disregard for their own safety. Adult chamois take 6 m (20ft) leaps, and can run down near vertical slopes as easily as they can run up them; and their young are able to keep up with them when just a few weeks old.

• COPING WITH WINTER

In tropical Mountains, conditions are often much the same all year round, which means that animals can stay at one altitude all their lives. But in temperate mountains, seasonal changes affect the food supply. WINTER is the critical time; anything that cannot survive the cold weather conditions and the shortage of food has to move to lower ground or hibernate until the return of spring. Animals that are RESIDENT at HIGH ALTITUDE have a variety of ways coping with the changes. Insects often enter a dormant state, called DIAPAUSE, which puts their development on hold. Many small mammals, such as MARMOTS, survive Mountain winters by hibernating, while many of those that remain active live on food stores accumulated earlier in the year. Pikas, for example, gather up leaves and grass and build them into “haystacks” among the broken rocks around their homes. Before adding fresh supplies to a stack, they sometimes spread them out to dry in the sunshine, which reduces the chances of the food rotting before it is eaten. For other animals, the first autumn snows are the signal to move downhill. These vertical migrations are a common feature of Mountain life in temperate regions, and they are demonstrated by a wide range of mammals and birds, from mountain sheep and deer to CHOUGHS and GROUSE. In many cases, the migration involves moving from the exposed mountain top to the forest lower down, but some mountain forest species also  migrate. Among these latter migrants are birds such as nutcrackers, which feed on CONIFER SEEDS. If the seed crop fails, they fly downhill in a form of sporadic migration called IRRUPTION. Clark’s nutcracker, from the Rocky Mountains, is a typical example: normally found at up to 2,500 m (8,200 ft.), it descends as low as sea level when food becomes hard to find. 

• FINDING FOOD

As in most land habitats, a mountain’s animal life depends ultimately on plants, for plants provide food for herbivorous animals, which are, in turn, eaten by a wide range of predators. However, some mountain animals make use of a very different food source – the cargo of small animals, mainly insects, that are carried uphill by the wind to be stranded among the rocks, snow and ice. Many of these wind - blown animals are so tiny that they are practically invisible: yet they provide useful nourishment for scavengers that live above the snowline. They consist almost entirely of invertebrates, such as springtails and snow fleas, which can survive the very low temperatures of high altitude winters. During the depths of winter, they hide among rocks and moss, but when the weather warms up they can often be seen hopping across banks of snow – feasting on the debris that the wind has brought up from lower ground.

• LIFE IN CAVES

Many animals use caves temporarily, but some have adapted to spend their entire lives in them. These permanent cave – dwellers, called TROGLODYTES, feed either on each other or on the droppings deposited by roosting BATS and birds. As a habitat, deep caves have the advantage that temperatures remain fairly constant throughout the year. However, they are also completely dark, which means that eyes are useless. Bats, oilbirds, and swiftlets use ECHOLOCATION to navigate while underground, but permanent cave - dwellers sense their surroundings largely by touch, often using smell to track down food. Cave crickets detect food using antennae, while spiders and harvestmen use their feet. In subterranean streams and pools, cave salamanders, such as the OLM, sense vibrations in the water. The cave fish has a row of pressure sensors along each side of its body that enables it to detect other animals several meters away. Although food is scarce, animal exist many kilometers underground and have even been found in pothole systems that have no direct contact with the surface except via water trickling its way underground.

• The ARCTIC AND ANTARCTIC are the coldest places on earth. The ARCTIC is partly frozen Ocean, hemmed in by large expanses of windswept tundra: the ANTARCTIC is an ice – covered continent, surrounded by the world’s stormiest seas. They are similar to each other and unlike any other habitat – in that they have 24 – hour daylight in summer and perpetual darkness in winter, but they are physically different in ways that have important effects on animal life. In the ARCTIC, many animals live on land: in the ANTARCTIC, animal life is based almost entirely in the OCEAN.

• ARCTIC AND TUNDRA

Covering about 12 million square km (4.6 Million square miles), the ARCTIC OCEAN is both the smallest and the shallowest Ocean in the world. For several months in summer, permanent daylight produces a constant supply of energy, which is harnessed by vast quantities of PLANKTONIC ALGAE. These form the first link in the ARCTICOCEAN’S FOOD CHAIN, which ultimately nourishes animals as large as WHALES and POLAR BEARS. Sea ice – or the lack of it, - is a major factor in determining where large mammals live, especially during winter when the surface of the ICE is at its greatest. Polar bears and Arctic foxes can traverse the ice to find food, but seals and some other Marine Mammals must maintain breathing holes to survive. Despite the icy conditions, sea life is plentiful in the ARCTIC because cold water is rich in oxygen and the sea – bed sediment is rich in nutrients. On land, though intense winter cold means that trees cannot survive. The result is tundra – an open, often featureless, landscape, scraped smooth by glaciers during the last ice age. Today, ARCTIC GLACIERS are restricted mainly to Mountains and to the ICE – CAP that covers GREENLAND, but large areas of tundra remain permanently frozen underground. This frozen zone – the PERMAFROST LAYER – prevents spring melt – water from draining away, creating waterlogged landscapes                     in a region where rainfall, or snow, is paradoxically very low. In later spring and early summer, tundra plants grow, and flower, very rapidly. Geese and other migratory birds arrive to breed, and vast numbers of mosquitoes emerge from tundra pools. The migrants’ departure, when the short summer draws to a close, marks the end of another biological year.  TRUE TUNDRA IS FOUND NORTH of the Arctic circle, but tundra – like conditions exist on some mountains elsewhere.

• ANTARCTIC

Unlike the ARCTIC, Mainland Antarctica is isolated from the rest of the world. It is covered with ICE, up to 4,000 m (13,200 ft.) thick, which continues out to sea forming large ICE SHELVES. On the Antarctic Peninsula - a finger of land pointing towards South America – Summer temperatures rise to a few degrees above freezing point, but in the rest of the continent average temperatures are below freezing all year round. Algae and lichens grow on bare rocks in many parts of the ANTARCTIC COASTLINE, but the ANTARCTIC PENINSULA is the only part of the continent where terrestrial plants can survive. This is also the only place that has a significant range of terrestrial animals, although these are chiefly springtails, mites, and nematode worms – few of which are over 5 mm (1/5 in) long. The rest of Antarctica’s land – based animal life consists of species that feed in the sea and come ashore to breed, such as PENGUINS, or those that scavenge food at these animals’ breeding grounds, such as Skuas. With the exception of emperor penguins, vertebrates desert the ice at the end of summer to spend the winter at sea. The Southern Ocean, which surrounds ANTARCTICA, is one of the most biologically productive seas in the world. Although species numbers are relatively low, population sizes are often enormous because the non – stop summer daylight generates a vast supply of food. Krill – small crustaceans that form the diet of SEALS and WHALES – are especially prolific: Some of their swarms are estimated to weigh in excess of 10 million tonnes and are large enough to be seen by satellites in space. Although the Southern Ocean is always cold, it maintains a minimum temperature of about – 1.8°C (28 .8°F): below this, seawater freezes. As a result, the Ocean is quite warm compared with Antarctica itself. MOST OF ANTARCTICA – excluding the relatively mild Atlantic Peninsula, lies south of the Atlantic circle.

• LIFE IN POLAR REGIONS AND TUNDRA (ARCTIC &ANTARCTIC)

Although they live at opposite ends of the EARTH, the animals that inhabit the Arctic and Antarctic share many adaptations. Resilience to extreme cold is first and foremost among these, but almost as important is the ability to cope with a highly seasonal food supply. For some animals, winter is a good time for catching food, but for most, hunger and cold make the long winter months a critical time of year. Such testing conditions mean that in comparison with other parts of the world the POLES are inhabited by very few animal species. However, those that do thrive can be extraordinarily numerous.

• COPING WITH COLD

Warm – blooded animals have to maintain a constant body temperature, which means that combating HEAT LOSS is a major priority in the POLAR ENVIRONMENT. Cold – blooded animals can function with a fluctuating body temperature, but even they have limits – in sub - zero conditions they freeze solid. Fish are particularly at risk of freezing, for while their body fluids normally freeze at about – 0.8° C (30.6° F). Polar sea water is often slightly colder still. To help prevent freezing, the blood of many cold – blooded species contains proteins that lower its normal freezing point. Some insects can survive at 45° C (- 49°F) without any ice forming in their bodies. Since mammals and birds cannot afford to let their internal temperature fall even slightly, they need insulation to keep warm. Fur and feathers are among the finest insulating materials that nature has devised, but many polar animals, such as WHALES, SEALS, and PENGUINS, have additional insulation in the form of BLUBBER – a layer of yellowish fat that is laid down under the skin. BLUBBER, which can be up to 30 cm (12 in) thick, is such an effective insulator that all these animals feel cold to the touch even when their internal body temperature is above 38° C (100.5° F). BLUBBER is particularly useful in the sea because water conducts heat away from the body 25 times faster than air. It also has another valuable function: because fat contains lots of energy, blubber can be used as a food reserve when supplies are low.

• SURVIVING UNDER ICE

WHALES and SEALS face problems during the long polar winter because SEA ICE restricts their access to air. They dive under the ice to feed, but they must then surface to breathe. Some species avoid the problem by moving to lower latitudes. Those that remain behind survive either by maintaining breathing holes or by congregating in POLYNIA – areas where the wind and currents keep the water ice – free. SEALS start making breathing holes when the ICE is thin, rasping away at it with their teeth. As the depth of the ICE increases with the progress of winter, they continue to visit and work on their holes to ensure they remain clear. WEDDEL SEAL, which lives further south than any other species, spends so much time keeping its breathing holes open that its teeth develop distinctive patterns of wear, and by late winter its breathing holes, can be 2 m (6 ½ ft.) deep. The SEALS have to find their holes in almost complete darkness because during the ANTARCTIC WINTER the sun stays below the horizon for weeks. Whales rarely make breathing holes. Instead they head for POLYNIA, where they can come up for air in open water. This less laborious strategy means they are not tied to one place, but it does have its dangers: groups of whales can become ensnared in shrinking POLYNIA, unable to reach the next stretch of open water. There are records of NARWHALS – the world’s most northerly whales – being trapped in their hundreds, making them easy targets for hunters.

• CHANGING COLOUR

In the treeless Arctic tundra, camouflage is one of the most effective ways both of avoiding attack and of making an attack unseen. The summer and winter landscapes look so different that many tundra animals change their camouflage twice a year. The Arctic fox is a classic example: its summer coat is usually brownish grey, but in early autumn it turns WHITE: in spring, the process is reversed so that the fox blends with the rapidly thawing tundra. In some parts of the far north – particularly western Alaska and northern Greenland – ARCTIC FOXES develop a bluish winter coat instead. Some researchers have suggested that this blue coat is an adaptation to coastal landscapes, where there is less winter snow, but as  these foxes have been widely introduced by fur farmers the theory is difficult to prove. The least weasel, the world’s smallest carnivore, changes its coat in a similar way, as do PTARMIGANS and many other tundra birds. Some, such as the snowy owl, keep their white plumage all year round, which suggests that good camouflage is most important in winter and less so in summer when food is easier to find.

• SUMMER MIGRANTS

Near the poles, 24 – hour daylight in summer creates the ideal conditions for rapid plant growth. This short - lived but profuse supply of food has a dramatic effect on tundra life, attracting vast numbers of migrants. Geese come to crop the plants with their beaks, waders arrive to feed on worms, and insects that live in swampy ground, while terns find food both on the tundra and in water close to the shore. This animal influx of visitors is mirrored in the sea. Many of the world’s baleen whales head towards POLAR WATERS during summer to make use of the annual upsurge in planktonic life.  However, unlike migratory birds, these huge mammals do not breed at high latitudes. Instead, they put on weight and then return to warmer waters to give birth. During the breeding season, they often do not feed at all.

• WINTER FOOD

Although the FOOD SUPPLY in POLAR SEAS slowly falls in autumn, there is still a reasonable amount for animals to eat. On land, life is not so easy. The growth of TUNDRA PLANTS comes to a complete halt and, to make matters more difficult, the plants themselves are often covered by deep snow. For herbivores, this lack of accessibility is a major problem at a critical time of year. In the ARCTIC TUNDRA – Plant – eating animals reach plants in one of two different ways. REINDEER (CARIBOU) and Musk OXEN use their hooves to clear away the snow to reveal the lichens and dwarf willows underneath. Lemmings turn the snow to their advantage for burrowing in it. The snow protects them from predators and from the weather outside: no matter how cold or windy it is on the surface; the lemmings enjoy a benign micro – climate that allows them to feed all year. In Antarctica, there are very few terrestrial plants, which means that almost no animals stay active in winter on food gathered from land. With so much ICE, even food from the sea can be difficult to reach. Male emperor penguins, guarding their eggs, do not even attempt to find it; huddling on the ICE through the long night of winter, they go without food until spring.

Every year, about 100,000 cubic km (24,000 cubic miles) of water evaporates from the world’s Oceans, condenses, and then falls as rain or snow. Most of this water disappears back into the atmosphere to continue this cycle, but about a third returns to the Oceans by flowing either over ground or beneath the land surface. This steady supply of freshwater sustains all the world’s land - based life, as well as creating highly diverse habitats – from STREAMS, RIVERS, and LAKES, to REEDBEDS, MARSHES, and SWAMPS – in which a wide range of different animal and plant life can thrive.

• LAKES AND RIVERS

For permanent water dwellers, life in lakes and rivers is shaped by many different factors. One of these is the water’s chemical make – up, which is often dictated by the type of Rock that forms the bed of a river or lake. Hard water, for example, is good for animals that grow SHELLS because it contains CALCIUM that can be used as SHELL – BUILDING MATERIAL, while water that is especially rich in OXYGEN is important for highly active predatory fish, such as SALMON and TROUT. Water that is very deficient in OXYGEN, on the other hand, provides a poor environment for animal life as a whole because relatively few aquatic species, apart from specialized worms can survive in it. In lakes and rivers, aquatic animals usually occupy clearly defined zones. The brightly lit water close to the surface often teems with water – fleas, copepods, and other microscopic forms of animal life. They live here in order to feed on PHYTO PLANKTON – the microscopic algae that become extremely abundant during the summer months. Feeding in the middle zone and near the water’s surface are larger animals, such as FISH, that are able to hold their own against the strength of the current. Weak swimmers live near the banks, where the current is slower, or among stones and sediment on the bottom. In still and slow – flowing water, surface tension supports insects that hunt by walking or running over the water. Some animals that are associated with FRESHWATER HABITATS are not necessarily permanent water dwellers; instead they divide their time between WATER and the adjacent land, entering the lake or river to hunt or breed, or using it as a nursery for their young. In geological terms, lakes and rivers are highly changeable. Lakes gradually fill with sediment, while rivers often change course.

• WETLAND

A Wetland is any waterlogged or flooded area with a covering of water plants. In some wetlands – reed beds and bogs, for example – the plants hide the water completely. However, in most wetland, areas of open water and dense vegetation are mixed, creating a rich and complex habitat that can be exploited by animals of almost every kind. Biologically, WETLAND is among the most productive inland habitats, sometimes surpassing even rain forest in the amount of food that it generates for animals. In temperate parts of the world, this productivity reaches a PEAK during spring and summer, but in the TROPICS and SUBTROPICS it is more affected by the water supply. Some tropical wetlands – South America’s Pantanal, for example – largely dry out during the dry season, but then look like vast lakes once it has rained. In many wetlands, the water is no more than a meter (3 ¼ ft.) or so deep, which means that bottom – living animals and surface dwellers are rarely far apart. This kind of environment is ideal for air - breathing swimmers, such as snakes and turtles, and also for land - based animals that use water as a temporary refuge from danger. Unlike large lakes, wetlands have an extra dimension in the form of emergent plants, which grow up through the water’s surface and into the air. These plants range in size from small grasses and rushes just tall enough to keep insects clear of the water, to water – loving trees that grow to over 35m (115 ft.) high. Trees act as important roosting and breeding sites for water birds, providing them with shelter and relative safety from predators as well as keeping them close to the source of their food. FRESHWATER WETLANDS – include the PANTANAL, South America, and the OKAVANGO, an inland delta in Botswana, Southern Africa.

• LIFE IN FRESH WATER

Fresh water is an essential resource for all land – dwelling animals, but it is also an important habitat in its own right. Fresh water habitats vary immensely, from temporary POOLS to giant lakes, and from tiny streams to rivers thousands of kilometers long. As a result, the problems that animals must overcome in order to survive in their environment can be very different from one freshwater habitat to another. Strong currents, periodic drought, and intense competition for food are some of the difficulties for which animals must find solutions.

• STAYING IN PLACE

Animals living in fast – flowing rivers face a constant battle with the current, and they cope with it in one of two main ways. The first is to avoid the problem by staying close to the RIVER – BED, where the current is relatively slow. Many invertebrates, such as STONEFLY and MAYFLY larvae, never – venture into open water; and to improve their staying power they often have a flat profile, so that if they position themselves with their heads facing upstream the current presses down on their backs, helping them to stay in place. Remarkably, the same technique is used by dippers -  the only songbirds that feed under water: they are naturally buoyant, but as they walk upstream cover, the river – bed, the force of the current keeps them submerged. The second solution is to complete with the current by swimming against it. Species that cannot avoid the current match their swimming speed to the water flow, enabling them to stay in place – and they keep swimming even when they are a sleep.

• MIGRATION

As well as supporting freshwater residents, rivers and lakes receive visitors from the sea. These are migratory fish, which divide their time between fresh – and salt water habitats. Anadromous species, such as SALMON, breed in rivers but spend most of their adult lives off shore. CATADROMOUS species, such as some EELS, do exactly the opposite: they live in freshwater, but swim out to sea to breed. For most fish, fresh water makes a much safer nursery than the Ocean, and this justifies their long journey up river to lay their eggs. However, because the food supply in fresh water is limited, the young eventually make for the much more dangerous, but also more fruitful, environment of the open sea. The advantages of this are apparent where some, but not all, members of a species migrate: those that swim out to sea usually grow much bigger than those that stay behind. Like migrating birds, migrating fish are often remarkably accurate in pinpointing the place of their birth, returning there to spawn even though it might mean an inland journey of over 2,500 km (1,500 miles). Each river has its own characteristic chemical fingerprint and, with their acute sense of smell, migratory fish are able to identify the estuary that they left as young fish. By monitoring the scent of the water as they progress up river, they home in on their own spawning ground. Migrating fish often meet barriers to their progress. SALMON are famous for jumping waterfalls and rapids, while eels tackle obstacles by slithering around them over land. Eels usually do this after dark, in damp conditions, when they can survive out of water by breathing through their skin.

• LIVING IN AND OUT OF WATER

Most amphibians, such as frogs and toads develop in freshwater habitats and then, as they approach adulthood, take up life on land, returning to water to breed. However, insects evolved amphibious lifestyles long before the first true amphibians appeared. Today, almost every patch of freshwater, from the smallest puddle to the largest lake is inhabited by insects. Mosquito larvae feed on microscopic freshwater life, whereas the larvae of dragon flies and damselflies stalk larger prey, catching it with a set of extensible jaws called a MASK. These insects leave the water when they become adult, but water beetles and bugs remain in it for life, although their ability to fly makes it easy for them to spread from one pool to another. Some larger animals have developed lifestyles that straddle water and land. Snakes are good swimmers, and a number of species, such as the grass snake, specialize in catching aquatic animals. The anaconda, the heaviest snake in the world, uses water for cover and for support; despite its size, water buoys it up, reducing its effective weight to almost nil and enabling it to swim at considerable speed. As well as providing food, freshwater is a valuable resource for some land – based animals seeking refuge from predators or daytime heat. At dusk, birds often roost on lakes and reservoirs while, during the day, hippos, capybaras, and beavers spend a lot of time in the water, emerging under the cover of darkness to feed on land.

• SURVIVING DROUGHT

In warm parts of the world – particularly in the tropics – rivers and lakes often dry out completely for several months each year. In these conditions, freshwater animals need some unusual adaptations to survive. When a lake’s water level drops, its temperatures increases. Warm, stagnant water often contains so little oxygen that many fish suffocate, but LUNGFISH – characteristic inhabitants of tropical lakes and wetlands are experts at coping with drought. They gulp air at the surface and, when their home starts to dry out, they burrow into the mud, sealing themselves inside mucous cocoons. Later in the year, when heavy rain falls and soaks the mud, the cocoon breaks down, and the fish wriggle away. Caimans and turtles also hide away in this manner, although their scaly, waterproof skins mean that Cocoons are not needed. Being “Cold blooded”, or ectothermic, they need relatively little energy to stay alive, so they can survive drought – induced food shortages for months. Animals that cannot survive drought often leave behind drought – resistant eggs, which hatch when water returns – an effective way of bridging the gap between one wet period and the next. This survival strategy is used by WATER FLEAS, ROTIFERS, TARDIGRADES, and many other “micro – animals” that live in temporary pools or in the film of freshwater that covers mosses and other plants.

• COMING UP FOR AIR

Freshwater animals need to breathe OXYGEN. Fish use gills to extract it from the water, but many invertebrates collect it from the air. These air – breathers include water snails, many insects, and water spider – the only spider to have evolved a fully aquatic lifestyle. For animals living at the water’s surface, air is easy to reach. For fully submerged ones, breathing requires periodic trips to the surface to replenish air reserves, which are stored in or on the insect’s body, often forming a film – like bubble that gives the animal a silvery sheen. The water spider has an exceptionally elaborate storage system. It constructs a “diving bell” from strands of silk, trapping a large bubble of air inside it. The bell acts as both lair and nursery – a unique example of an animal creating a submerged habitat that resembles dry land.

• LIVING IN SALT LAKES

Salt and soda lakes are the most saline habitats on earth, with up to 10 times as much dissolved salt as the sea. They form where rainfall is low and evaporation rates are high because temperatures often climb  to cover 40°C (104°F). Relatively few animals can cope with these extreme conditions, but the ones that do can be extremely numerous because they face very little competition. Salt – lake food chains are based on CYANOBCTERIA – plant like micro – organisms that harness the energy in sunlight, turning it into food.

In the natural world, the boundaries between different environment are often rich habitats for wildlife. The world’s coasts are the ultimate example of this meeting of habitats because they bring together animals that live on the land and those that live in the sea. Coastal wildlife varies according to local conditions but, in rocky coasts as well as sandy ones, shore animals are associated with clear – cut zones that are usually determined by the tides. CORAL REEFS are special Kind of coastal habitat. Famed for their spectacular shape and color, they can grow to vast proportions and are unrivalled in the immense variety of aquatic life that they support. Reef- building corals require specific conditions, the most important being warmth and bright sunlight all year round. As a result, CORAL REEFS are largely restricted to the tropics.

• COASTS

Some habitats look much the same from one year to the next, but the SEASHORE is always changing. Waves pound away at rocks, undermining them and breaking them up, while COASTAL CURRENTS reshape the shore in a less dramatic way by moving shingle and sand. Super imposed on this is the rhythmic movement of their tides – a twice – daily circle that has a profound impact on seashore wildlife. Tides vary enormously in different parts of the world. Around islands in mid – ocean, the total rise and fall is often less than 30 cm (12 in), while in deep bays and inlets on continental coasts it can be over 10m (33ft). Whatever its height range, the tide – divides the shore into three different zones, each with its own distinctive animal life. The highest of these zones is the Supralitoral, which is the part of the shore just beyond the reach of the highest tides. Although this zone is never actually submerged, it is affected by salt spray, which means that animals that are sensitive to SALT – and also SALT – INTOLERANT PLANTS – are rarely found in this zone. Below this is the littoral, a zone that is regularly covered and then exposed as the tide floods and recedes. The animals found here, such as mussels and limpets, lead a double life in that they have to be able to survive both in water and in air. The next zone, or INFRALITTORAL, is always submerged, even during the lowest tides. Most of the animals that live in this zone are fully MARINE, although a few leave the water to breed. Coastal wildlife is also affected by the geology of the shore. Many animals live on ROCKY COASTS, while others specialize in living in sand or coastal mud. Compared with these, SHINGLE is a difficult habitat for animals, although some shoreline waders use it as a place to nest.

• CORAL REEFS

There are two (2) main types of CORAL: HARD and SOFT. Coral reefs are formed by hard corals. The individual coral animals, called POLYPS, secrete external skeletons that persist after they die. SOFT CORALS are found all over the world, but hard, reef – building corals grow only in clear, nutrient – poor water, where their symbiotic algae can harness the energy in sunlight. Such is the richness of the habitat created by CORAL REEFS that a huge number of animals are able to live side by side without competing for the same food. There are three (3) main types of REEF: fringing reefs, which grow close to the SHORE; barrier reefs, which are separated from the coast by deep channels, sometimes over 100 km (62 miles) wide; and ATOLLS, which are ring – or horseshoe – shape reefs that grow around oceanic islands, often where volcanoes have subsided into the sea. Although every reef is unique, REEFS share a common structure. Depth and exposure are two important factors that influence this because CORALS vary in their need for light and in their ability to withstand the force of the waves. The fastest – growing corals, which need lots of light and relatively calm water, typically form the CENTRAL ZONE OF THE REEF, projecting just above the surface at the lowest tides. On its inshore edge, the CENTRAL ZONE is often backed by LAGOONS – large pools of open water lying over coral sand. By contrast, the seaward edge of the reef often forms a submarine cliff that drops steeply into the depths. The corals in this zone are solid and resilient because they have to withstand heavy breakers rolling in from the open sea. CORAL REEFS ARE FOUND IN PARTS OF THE WORLD when the sea temperature never drops below about 18°C (64°F). The world’s largest reefs are in the Indo – Pacific region.

• LIFE ON COASTS AND CORAL REEFS

Compared with the OPEN SEA, coasts and coral reefs are disproportionately rich in marine wildlife. Rocky coasts and mudflats abound with seabirds and invertebrates, while coral reefs probably contain at least a third of the world’s fish species. Conditions in coasts and reefs are variable, so the animals that use them are often extremely specialized. Some roam over large areas of the SHORE, but for most a distance of just a few meters makes the difference between an ideal habitat and one in which it is impossible to survive.

• ADAPTING TO TIDES

For coastal animals, life is governed by the rhythm of the tides. As well as adapting to the twice – daily ebb and flow, they have to adapt to the drawn – out rhythm of extra – large spring tides, which are normally 14 days apart. Knowing where the tide stands is important because animals caught unprepared run the risk of either drying out or drowning. Some shore animals, such as BARNACLES, adjust their behavior according to whether or not they are submerged. Most aquatic animals, however are much more sophisticated, reacting to their internal biological clocks, which march in step with the tides. Even if they are taken away from the SHORE and placed in a tank, their tidal clocks continue to tick. This in – built ability to keep time enables animals to anticipate events. For example, submerged LIMPETS crawl over rocks to graze on microscopic algae. But since they are vulnerable away from their niche on the rock, they have to return home before the sea ebbs away. Their biological clocks tell them when to head back, ensuring that they are securely in place, and airtight, before the tide goes out. Conversely, the fiddler crab’s biological clock prompts it to come out and feed at low tide and then return to its underground burrow before the incoming tide engulfs it.

• FEEDING ON THE SHORE

Coasts provide a much greater variety of food than the OPEN SEA. High up the shore, an abundance of animal and plant remains left in strandlines by the retreating tide are consumed by beach – hoppers, spring tails and other scavengers, which are then preyed upon by GULLS and WADERS. In the intertidal zone, filter – feeders are common. Unlike the giant filter -feeders of the OPEN SEA, coastal ones are generally small and often spend their entire adult lives fixed in one place. MUSSELS and other BIVALVES, which filter particles of food using modified gills, are examples of these. BARNACLES have a different filtering technique: despite their resemblance to MOLLUSCS, BARNACLES are crustaceans, with a set of feathery legs. At high tide, the legs protrude from the barnacle’s case to collect food particles. Rocky shores are home to some fast – moving swimmers as well as to many other animals that take a more leisurely approach to find food. STARFISH and SEA URCHINS are among the slowest, crawling over rocks on hundreds of fluid – filled feet.

• LIVING IN MUD AND SAND

Compared with rocky shores, coastal mud and sand seem to harbor only a limited amount of animal life. But appearances are deceptive. MUD in particular often teems with hidden life feeding on organic matter brought in by the tide. One of the advantages of living below ground is that despite the attacks of CURLEWS and other long – billed birds, it provides good protection from predators. The chief disadvantage is that the surface is constantly shifting, cutting off buried animals from the water above – and from oxygen and food.  Some of these buried animals have specialized body parts that enable them to connect with the surface. CLAMS, for example, have leathery tubes or siphons. In many species the siphons can be retracted inside the shell, but in some they are too long to be stowed away. Species that do not have such accessories often live in burrows. The LUGWORM is an example: it makes a u – shaped burrow, lining it with mucus to keep it intact so that seawater does not make it collapse.

• MANGROVE SWAMPS

Mangrove swamps are formed by trees that are adapted for life in salty intertidal mud. Found only in the tropics and subtropics, they play an important ecological role by stabilizing the COAST and providing inshore nurseries for fish and other marine animals. Most mangroves develop arching PROP ROOTS, which are exposed when the tide is out and submerged when it is in. These provide anchorage for MOLLUSCS, and act as convenient perches for MUDSKIPPERS – the air – breathing fish that thrive in this habitat. Mangrove foliage is tough and leathery, and eaten mainly by insects: but the dense canopy attracts large numbers of birds, which use Mangroves as breeding sites and overnight roosts. The mud in mangrove swamps is deep and often foul – smelling, but it is rich in organic matter that is replenished each day by the tide. Until the late twentieth century, mangroves escaped much of the large scale deforestation in the tropics. But, with the increase in shrimp farming, large areas of mangroves have been cut down, raising concerns about the long – term impact on coastal wildlife.

• SYMBIOTIC PARTNERSHIPS

Symbiosis is a feature of life in all habitats, but it is particularly apparent on COASTS. In some cases, the symbiotic partners are animals; but, in many others, one is an animal and the other is microscopic algae that live inside its body. These algae, known as ZOOXANTHELLAE, can be found in thousands of coastal animals, including CORALS, JELLY FISH, and GIANT CLAMS. ZOOXANTHELLAE live by photosynthesis – the same process by which plants grow. Through a complex series of chemical reactions, they harness the energy in sunlight and use it to build up organic matter. The host animal provides ZOOXANTHELLAE with protection from the outside and, in return, the algae surrender some of their manufactured food. These partnerships are very important to reef – building corals because they allow them to live in places where the supply of food is otherwise low. For the partnership between CORAL and ALGAE to work, the corals have to encourage algae growth, which means they must live in bright sunshine near the water surface. However, this limits their upward growth because few corals can survive more than an hour of exposure at low tide.

• REPRODUCTION

Many land animals have adapted to life at SEA. Some are now fully MARINE, but others such as TURTLES, some SEA SNAKES, and SEALS and their relatives – must come ashore to breed. These animals are often scattered over the wide area, so they tend to form COLONIES during the breeding season, congregating in the same place each year to maximize their chances of finding a mate. Many coastal invertebrates, on the other hand, spend their entire adult lives in one place. For them, reproduction is an opportunity not only to multiply but also to disperse. Their eggs hatch into PLANKTONIC LARRVAE, which may then drift long distances in coastal currents before eventually settling down. For some species, such as BARNACLES, choosing a home is an irrevocable decision because a larva cannot detach itself once it has settled. Chemical cues help it to “make up its mind” before it takes this momentous step. Some fish come inshore to breed because the SHORELINE offers plenty of hiding places for their eggs. An extreme example of such a fish is the CALIFORNIA GRUNION, which lays its eggs not in water but in damp sand on beaches. GRUNLONS stage mass spawning’s during high spring tides at night. At the next spring tides, the eggs hatch and the young are washed into the sea.

The OCEANS FORM by far the largest continuous habitat on EARTH, and they were almost certainly the environment in which life first evolved. The underwater landscape is made up of mountains and volcanoes, cliffs, deep valleys, and vast, flat plants, many of them far larger than any found on LAND. The Oceans are so immense – they cover more than three quarters of the earth’s surface – and difficult to explore that scientific knowledge of OCEAN WILDLIFE lags behind that of life on land. However, research has shown that life is found at all levels, from the sunlit surface to the deepest trenches over 11km (7 miles) down.

• INSHORE WATERS

Some inshore waters are so shallow that if the world’s oceans were lowered by just 75m (245 ft.), huge areas of SEABED would be exposed. Off western Europe, for example, the COAST would be extended by about 200 km (125 miles), and in parts of SIBERIA (RUSSIA) by more than 700 km (435 miles). These shallow waters owe their existence to continental shelves – the gently sloping plateaux that flank many of the deep ocean basins. Continental shelves are a key habitat for SEALIFE, supporting large shoals of fish and a diverse collection of other animals, from LOBSTERS and CRABS to MOLLUSCS and burrowing worms. This wealth of life is possible because, in shallow water, Sunlight can reach the sea bed, promoting the growth of algae, sea grasses, and countless other organisms that need energy from light to survive. Just like plants on land, these provide animals with a year – round supply of food, as well as with plenty of cover and places to breed. Some inshore animals, such as LOBSTERS and FLAT FISH, spend most of their lives on the SEABED, while a few live entirely in mid – water or at the surface. Others live in quite different habitats at different stages of their lives. For example, some larvae develop as part of the surface plankton, then move to mid – water or the SEABED as adults. Inshore waters are also visited by animals from the OPEN SEA – most often by passive drifters, such as Jellyfish, but also by powerful swimmers such as WHALES and SHARKS. Some come to breed, while others arrive by accident and then return to deeper water. Occasionally, the latter get into difficulties; jellyfish often end up on the shore, and whales can become stranded when their navigation system guide them into shallow water instead of safely out to sea. CONTINENTAL SHELVES vary in width from a few kilometers – in coasts close to deep sea trenches – to over 1,000km (620 miles).

• OPEN SEA

Even in the clearest seawater, light penetrates no further than about 250m (825 ft.) below the surface. More than any other factor, this has a crucial effect on sea life because it determines what there is to eat. In the brightly lit surface zone, microscopic algae grow by harnessing the energy in sunlight, creating an invisible harvest for planktonic animals. This food is passed on when the PLANKTON are themselves eaten in food chains that eventually end with sharks and other large predators. Below the point where the light fades and finally disappears, there is no home – grown supply of food. At this depth, and further below, animals feed either on each other or on the supply of dead remains that constantly drifts down from the surface. Despite the un imaginable volume of the Oceans, few of the world’s animal species – perhaps 5 percent – live in open water. Since most of these stay near the surface, where they can take advantage of the relatively plentiful food supply, animal life in the huge mid - water zone and the deeper abyssal zone is comparatively sparse. In contrast with these central zones, much of the SEAFLOOR abounds with animals. Deep – sea creatures, which are known collectively as BENTHIC ANIMALS, include species that swim or crawl over the SEABED as well as those that burrow through it, mining the soft sediment for food. Many of these animals appear to have changed little over millions of years, for although the water is extremely cold, and the pressure intense, the deep – sea bed is not subjected to the changeable conditions that can affect the surface. It is therefore one of the most stable habitats on EARTH. IF THE CONTINETAL SHELVES are excluded, the average depth of the world’s Ocean basin is about 4,000m (13,200 ft.).

• LIFE IN OCEANS

In the billion or more years since the first animal species evolved, competition for survival in the sea has become intense. Today, the Oceans are home to the largest predators on the planet, as well as to vast numbers of microscopic animals that drift unseen. As on land, OCEAN WILDLIFE is affected by local conditions, the most important being the supply of food. For many, survival also depends on being able to defend themselves against attack. In some regions, life is thinly spread, but in others animals are found in greater numbers than they are anywhere else on earth.

• FEEDING AT SEA

The Oceans ae so huge that, although they contain plenty of nutritious food, marine animals face a challenge in finding enough to eat without expending too much energy in the process. Some concentrate on large prey. The sperm whale, for example, hunts giant squid at depths of over 1,000m (3,300ft), although most pursuit – hunters search for food near the surface rather than in the depths. Other large sea animals eat smaller fare, scooping it up in huge amounts, often sieving it out with their gills. This technique, known as FILTER FEEDING, is used by BALEEN WHALES and some of the largest SHARKS and RAYS. Most filter feeders live on PLANKTON, which is so abundant that it allows them to reach a gigantic size. Drifting Animals also feed on PLANKTON, although on a much smaller scale. COMBJELLIES or SEA GOOSEBERRRIES, for example, haul it in with stinging tentacles that work like fishing nets. On the SEABED, animal life depends almost entirely on the dead organic matter that drifts steadily down from above. Brittle stars are tropical of these scavengers, collecting food particles with their arms. However, there are also predators – bizarre fish, for example – that hunt in the total darkness on or near the SEABED. A normal life at the bottom of the sea can be sparse, so these predators cannot afford to miss any opportunity to feed. Many of them therefore have gigantic months and elastic stomachs that enable them to swallow prey that is almost as large as themselves.

• CONTROLLING BUOYANCY

Very few marine animals – with the exception of deep – diving mammals – are found at all levels in the sea. Instead, most are adapted for life at a particular depth, and have buoyancy devices that help to keep them there. Surface drifters, such as the violet sea – snail, have simple floats: filled with material that is lighter than water, they ensure that the animal stays at the surface, even in a heavy swell. For animals that spend their lives fully immersed, remaining at one level requires more complex apparatus. They have to be neutrally buoyant at their optimal depth and yet able to rise or sink as the need arises. To do this, some use adjustable buoyancy aids hidden inside their bodies. BONY FISH, for example, have a gas filled chamber, called the SWIM BLADDER, just below the backbone. If the fish needs to sink, it removes some of the gas from the swim bladder by pumping it into the bloodstream: if it needs to rise, it pumps it back into the bladder: Cartilaginous fish, such as SHARKS, do not have swim bladders: instead they rely on their large oily liver to keep them afloat. Many sharks are actually slightly heavier then sea water: swimming provides the lift that allows them to control their depths.

• AVOIDING PREDATORS

In the open sea, there is nowhere to hide, which leaves animals highly vulnerable to predators. To survive, some rely on camouflage or disguise: Others behave in ways that make them difficult to attack. For slow – moving invertebrates, such as those that make up PLANKTON, one of the most effective disguises is transparency. PLANKTONIC ANIMALS are often as clear as glass, which makes them difficult to see, even at close quarters. Most of these animals are only a few millimeters long, although some tunicates form translucent, tube – shaped colonies that can be over 3m (9 ¾ ft.) in length. Some fish are transparent when they are very small, but then use CAMOUFLAGE of a different kind as they get older. Almost all species that live in brightly lit, open water have dark backs but much paler undersides. This pattern, known as countershading, protects fish in two ways; it hides them from predators deeper down by disguising their SILHOUETTE against the bright sky, and it conceals them from surface hunters, including seabirds, by making them blend in with the dark water beneath.

• BIOLUMINESCENCE

A variety of marine animals produce light – some to maintain contact with their own kind, others to lure prey. In some species, notably PLANKTONIC invertebrates, the value of light is less easy to explain. BIOLUMINESCENCE is most common in BATHYPELAGIC SPECIES (those that live in very deep, open water). Typically, the light is produced by skin organs called PHOTOPHORES. Light production is not always confined to the animal itself: some fish can eject luminous clouds to distract predators while they make an escape.

• LIVING IN GROUPS

On land, animal groups can be very large, but none rivals the size of those that can occur at sea. Fish often live in SHOALS thousands or even millions strong, while some PLANKTONIC ANIMALS form swarms that can be over 100k (600 miles) long. These giant aggregations of underwater life often seem easy targets for predators. WHALES gorge on KRILL with almost nonchalant ease, while other predators make huge in roads into shoals of fish. But, in general, animals living in groups are safer than they would be alone: they are more difficult to single out and much more difficult to take by surprise. A few animals, such as DOLPHINS, live in sophisticated social groups. Dolphins use ECHOLOCATION to locate prey, to warn each other of danger, and to organize themselves during hunting.

• MIGRATION

Many marine animals – including most the largest whales – migrate between breeding grounds in the tropics and feeding grounds at higher latitudes. The GREY WHALE probably travels the greatest distances: its lifetime annual migrations total up to 800,000 km (500,000 miles) – twice the distances to the moon. TUNA are also known to undertake immense journeys: some shoals travel the length of the MEDITERRRANEAN; in the pacific, one fish tagged in Mexico was recovered off Japan. TURTLES show very precise migration patterns, returning to the same stretch of beach year after year to lay their eggs. This is all the more remarkable because it takes two or three decades for the animal to mature: during this time a turtle remembers precisely where it hatched so that when it is ready to breed it can make the long journey back. On a smaller scale, many fish swim inshore to spawn, while other slow – moving animals migrate across the sea bed. CARIBBEAN SPINY LOBSTERS travel between shallow reefs, where they breed, and deeper water, where they over winter; they set off in single file, each one following the tail of the animal in front. Journeys like these are usually annual events. But some animals migrate daily to feed. PLANKTONIC ANIMALS often rise to the surface at night, sinking back into the depths by day. Some of the plankton’s predators copy this pattern, creating a 24 – hour cycle involving many animals. These vertical migrations are clearly revealed by shipboard sonar, which shows a reflective layer rising at sunset and sinking at dawn.

• HYDROTHERMAL VENTS

First seen in 1977, off the GALAPAGOS ISLANDS, HYDROTHERMAL VENTS are remarkable ecological oases on the deep – sea bed. Vents are created by volcanic activity releasing streams of intensely hot, mineral – laden water into the Ocean. They are among the few habitats where life does not rely on energy from the sun – specialized bacteria use the minerals to produce energy, and vent animals either consume food created by the bacteria or eat each other. Over 3000 animal species have been discovered around vents; most of these are not found elsewhere.

Two hundred years ago, only about 3 percent of the WORLD’S POPULATION lived in cities. Today, the figure is rapidly approaching 50 percent, and the HUMAN POPULATION has increased nearly six fold. This phenomenal growth in urban living has transformed large areas of the planet. It has created a wide range of artificial habitats both in and out of doors – that animals can use as their homes, as well as vast amounts of waste that form the basis of animal food chains. As a result, there is a wealth of wildlife living with and among us.

• OUT DOORS

For animals that can cope with disturbance, cities and towns can be good places to live. They have plenty of suitable places for sheltering or raising young, from trees and window ledges to underground passage ways, and for omnivorous species they provide a constant supply of leftover food. In winter, the artificial heat that escapes from buildings offers additional benefit. Even better: cities are relatively safe: cats and dogs aside, they are free of many of the predators that animals would face in their natural homes. Animals have adapted to urban expansion with different degrees of success. Some species are never found in cities, always retreating as the concrete advances. Others, such as migrating birds and insects, are occasional visitors, touching down briefly before moving on. More adaptable animals – raccoons and red foxes, for example – are equally at home in town or country, and treat built – up areas as extensions of their natural habitat. True urban specialists, such as the ubiquitous feral pigeon and the house sparrow, are now so fully adapted to city living that they are rarely seen anywhere else. While feral pigeons can survive in the busiest city centers, many urban animals are found chiefly in parks and gardens – the small – scale versions of their habitats in the wild. These animals vary from one part of the world to another, but they include tree – dwelling mammals, such as squirrels and opossums, and a wide range of birds. The spread of suburbia is normally a threat to wildlife, but for these species it can actually be a help because it creates a patchwork of suitable habitats, sometimes with the bonus of food hand – outs.

• INDOORS

In the natural world, many animals in advertently create habitats for other species when they build their nests. Humans do exactly the same. However, because our “nests” are so extensive and complex, they can host an exceptionally wide range of animal life. Much of it is harmless, but some can cause problems or at least inconvenience. Most indoor animals are small and nocturnal, which helps them to avoid being noticed by their human hosts. This is especially true of species that share daily living areas and that scavenge leftover food. Silver fish, for example, emerge after dark to search for flour and other starchy produce, scuttling away if cupboards or drawers are suddenly opened, exposing them to the light. Cockroaches behave in a similar way, but they are more of a nuisance because they spread disease. At dawn, nocturnal animals hide away, leaving the day shift to take over. Houseflies, for example, are most active during the day because they navigate by sight. In basements and attics, wildlife is less affected by the cycle of light and dark, and it is less frequently disturbed by human comings and goings. For wild animals, attics resemble extra – large tree – holes, while basements resemble caves. Wasps, birds, and house mice will all nest in attics – if they can get in and they sometimes share this habitat with roosting bats. Basements and cellars provide a haven for spiders, which can survive for long periods without food and, in many cases, catch their prey in total darkness. The advent of central heating has been an important factor in the increase in the number of animals that choose to share our homes. For example, cockroaches, which were originally found mainly in warm parts of the world are now widespread in cooler regions. Soft furnishings and carpeting also play a part: as well as helping to keep the home warm, they provide hiding places and nesting material for various animals.

• LIFE IN URBAN AREAS

Animals have had millions of years to adapt to earth’s natural habitats, but only a fraction of that time to adjust to life in cities. Despite this, animals are never far away in built – up places. Their success is owed mainly to “preadaptation” – characteristics that evolved to suit one way of life, or habitat, but that accidentally turn out to be useful for another. Thus, some animals thrive in man – made habitats that resemble the ones they would use in nature. Others succeed because they are highly adaptable and can exploit the opportunities that we in advertently provide.

• FEEDING

Some outdoor urban animals live on the same foods that they eat in the wild, but for scavenging species – such as raccoons, foxes, and pigeons – the daily fare is often very different to that of their natural homes. These versatile creatures will try any kind of leftover food, however unfamiliar it looks and smells, and this highly opportunistic streak is the secret of their great success. Modern food packaging can sometimes present problems, but they quickly learn how to tear or peck away at plastic and paper to get at the edible contents within. Indoor animals get their food from one of three source: the things we eat, the animals that eat those things, and the fabric of our homes. The first category contains a wide range of house hold pests, such as rats, mice, house flies, and cockroaches: the second category consists chiefly of spiders, but also centipedes and geckos in warm parts of the world. Spiders are almost perfectly adapted to indoor life, and although widely disliked, they make a positive contribution by keeping indoor insect numbers in check. Animals in the third category are the least welcome of these uninvited guests. They include wood eaters such as termites and beetles, as well as insects that attack other organic materials such as wool. In many parts of the world these animals are serious pests.

• LIGHT AND WARMTH

In cities, street lamps light up the night sky, while heat from buildings and traffic makes them far warmer than nearby country side. Artificial lights confuse insect navigation systems and interfere with birds’ biological clocks. As a result, songbirds sometimes sing late at night, and some species start building nests in winter, convinced by the bright light that it is spring. Extra warmth is appreciated by a range of animals, from butterflies to birds. In some regions, starlings commute into cities on winter afternoons to roost on buildings where they are relatively warm.

• ROOF TOP ANIMALS

For birds and bats, the tops of buildings can make ideal homes. High above the ground, and relatively undisturbed by people, animals feed and breed unmolested. Some species nest in attics or under caves, while others favor the tops of chimneys. Swifts, swallows, and martins are foremost among rooftop – dwellers and are prime examples of preadaptation at work: they naturally nest on cliffs or in crevices, but the rapid spread of towns and cities has provided alternatives that have enabled them to extend their range to places where they would otherwise be rare.

INTRODUCED SPECIES

• Species that have set up home in unfamiliar parts of the world are plentiful in urban areas. Some have been introduced deliberately, while others arrive with imported food. Pets, also, are sometimes released, or manage to escape into the wild. Some of these animals remain urban, but a few – such as the STARLING in North America have gone on to colonize entire continents.

• STRUCTURAL PESTS

Since humans first started to build timber houses, wood -   eating insects have been a problem. Wood – eating beetles are common in temperate regions, while termites attack timber in the tropics. At one time, little could be done to control severe attacks; today, insecticides are effective at keeping them in check. Even so, many of these animals, especially wood – boring beetles are far more widespread than they were because they have been exported in the timber shipped all over the world.

• URBAN HUNTERS

The peregrine falcon is one of the most adaptable of all birds of prey. It feeds mainly on other birds, which it usually catches in mid – air. City rooftops and ledges provide an excellent vantage point for the falcon to pick out its quarry before launching into a high – speed downwards dive, known as a STOOP.