Mysterious Nature

Although human beings have achieved a great deal and discovered many things, even today there is still much about the natural world that puzzles the experts. As these mysteries are gradually uncovered by explorers, biologists and naturalists, they reveal a world of astonishing complexity and beauty. Just some of the many exciting discoveries that have been made in recent years are featured on the following pages.

What strategies do plants use to survive ?

Amazing adaptive and regenerative abilities are a plant's most important survival strategies. This is why plants can be found growing in the most extreme locations from deserts to mountains. Some plants are able to withstand high salt concentrations and periods of drought, while others survive temperatures as low as -80°C. If a plant is injured or suffers some other form of stress, its recovery will often be amazingly rapid.

Why are flowers colourful ?

Red, orange, yellow, blue and lilac-whatever the hue, the spectacular colours of flowers are all tools in the service of reproduction. Plants use the bright colours of their blooms to attract pollinators such as insects and birds. This also explains why the flowers of plants that are pollinated solely by the wind, such as grasses, tend to be rather nondescript. They don't need to look attractive.

Some flowers, like that of the horse chestnut, will even inform their pollinators when it's no longer worth paying them a visit. Brown stains develop inside the bloom as soon as it has been fully harvested and is empty. Pollinators then lose all interest in the flower and can target other, more inviting blooms.

What are deception flowers ?

Plants use many tricks to Plants deceive insects in order to attract them for the purpose of pollination. The aptly named deception flowers, for example, lure pollinating insects with a perfume that appears to promise a rich source of food, even though the plant doesn't actually deliver on the promise. Various orchids, such as the fly orchid, look and smell remarkably like the females of the insect species that are responsible for pollinating them. This encourages the insects to fly from flower to flower in a mating frenzy, transferring pollen in the process. Carrion flowers imitate the smell of dung or carrion which attracts flies that then lay their eggs. The unfortunate maggots, when they hatch from the eggs, simply starve to death.

Do plants speak to each other ?

Plants communicate using a chemical language, using scent as the means for sending and receiving information. Some plant vocabularies contain more than 100 chemical 'words' which are used to exchange information about pests or to call for assistance. If caterpillars snack on some maize, for example, the plant will produce 'alarm chemicals' that can be detected and recognised by the ichneumon wasp. The insect lays its eggs in the caterpillars and this ultimately kills them. Tomatoes that are nibbled by caterpillars produce toxins to combat the pests and emit a scent which warns other tomatoes. The essential oils contained in popular herbs such as sage and oregano also serve as a means of communication. They tell pests to keep away, while attracting pollinating insects.

Can plants move ?

Plants certainly do move, although they are not generally able to move away from a particular location. As they grow, the stalks may make swinging and circling movements as they bend towards the light and grow upwards against gravity. When plants actively close their flowers or leaves at night, scientists sometimes speak of the movements as 'sleeping'. Clovers, for example, fold their leaves at night so that the two external pinnae are wrapped inside the central one. To enable the pinnae to fold in this way, each one is equipped with a tiny joint located at the base of the leaf stem. This is pumped up by hydrostatic pressure, thereby causing the required movement. Biologists are not entirely sure of the reason for this pattern of movement, but they suspect that the leaves are seeking protection from nocturnal cold.

How tall can trees grow ?

No tree can keep growing taller and taller indefinitely the limit is reached at around 130 m. The reason for this is the way in which water is supplied to a tree's crown. The supply is made possible thanks to water evaporating through the stoma on the leaves. This produces suction, which moves water from the roots to the crown through a vascular system. However, above a height of 130 m this pull becomes so strong that it ruptures the water column. This is because gas bubbles, formed as a result of the extremely low pressure in the water column, interrupt the flow. Botanists describe this process as embolism.

The tallest living tree in the world at present is thought to be a sequoia in Northern California's Humboldt Redwoods State Park. At 113 m, this massive conifer is as tall as a 25- to 30-storey building. However, there are records of an Australian mountain ash that grew even taller. In 1872, a tree felled in Victoria was measured at 132.58 m. With the addition of the tree's stump and the material trimmed from the crown of the tree, it probably exceeded 150 m in height when growing. 

Where do the world's oldest trees live ?

Trees die of old age, like all living things, but they can take quite a bit longer to do so. Even some common conifers can have an average lifespan of between 300 and 600 years- several times that of any human being. At around 1000 years old, oaks and yews are the Methuselahs of temperate latitudes.

The current record for the world's oldest known tree is held by the Rocky Mountains bristlecone pine, which is found in California's White Mountains. More than 4000 years must pass before many of the trees begin to show signs of dying from old age, with the current record holder still alive after 4700 years. Bristlecone pines are very robust, needing little in the way of moisture and nutrients. Inconspicuous and unremarkable, they don't grow much above 12 m in height, which is probably why scientists didn't realise until the 1950s that they lived for such a very long time. Before their great age was established, everyone agreed that the huge sequoias - some of which were between 3000 and 3600 years old - were the oldest trees on our planet.

How does a seed know when to germinate ?

Many seeds go through an initial stage of dormancy to ensure that they don't begin to germinate too early and under unfavourable conditions. Depending on the species and the prevailing environmental conditions, the seed will spend this period of dormancy waiting for various signals before they germinate.

In the desert, for example, it is important that plants shouldn't start growing until there is sufficient water to support them, which is why the seeds of desert plants store germination-inhibiting substances in their outer coatings. These substances must be rinsed out by strong, long-lasting rain before the seeds can germinate - a short shower isn't sufficient to do the job.

To ensure that autumn-flowering plants don't start to grow until after the winter is over, their seeds are not ready to germinate until they have been exposed to low temperatures and frosts. Some fruits, including tomatoes, contain a substance called abscisic acid, which prevents their seeds from germinating immediately. After winter dormancy, when conditions are favourable, other substances are produced which signal that the time is right for germination.

Why are fruits usually sweet ?

Fruits are sweet to make them palatable to animals, and they generally also have eye-catching skin colours to make them. clearly visible. Fruit contains seeds, stones or kernels which are swallowed by animals and excreted in a different location. In this way the plant distributes its seeds as widely as possible and maximises its chances of reproducing. Depending on the area covered by a moving animal, the seed may be distributed anywhere from just few metres to several hundred kilometres away from where it originated.

Some seeds actually have to be eaten because they can only germinate after they have passed through the gut of an animal. This strategy also ensures that the germinating seed is provided with a good supply of fertiliser, since it is expelled at the same time as a quantity of excrement.

What is the juice in a coconut for ?

Coconut juice, or coconut water to be more precise, is liquid food for the coconut tree seedling. The sweet, almost transparent liquid is full of nutrients, containing oil, sugar, water, vitamins and minerals, including potassium, phosphorus and selenium. As the fruit ripens, the hard coconut flesh absorbs the water. As a rule, it is true to say that the riper the fruit is the less water it will contain. Coconut water is sterile and can therefore be used in an emergency as a substitute for serum and injected directly into a vein in cases where there has been major blood loss.

Is a strawberry really a berry ?

The answer is no. In botanical terms, a fruit is the mature ovary of a flower within which seeds develop. The soft outer flesh of a true berry is formed by the ovary's outer wall and contains one to many seeds within. Examples are tomatoes, grapes and even oranges. Technically speaking, strawberries are not true berries, but aggregate fruits. Each of the little dots studding the outside is itself a fruit, known as an alchene. A nut is similar to an alchene but has a hard, dry outer ovary wall.

Why is vanilla so expensive ?

Vanilla comes from a plant that belongs to the orchid family, to a genus with more than 100 different species. Evergreen perennials, they climb up trees, bloom for no more than a few hours and will only develop a fruit if they are pollinated by insects during this period.

Because of its shape and leathery appearance, the fruit of Vanilla planifolia is called a pod, but the correct botanical term for it is a capsule fruit. It forms from the ovary and several fused petals, and bursts open after it has dried, spreading its seed.

In the industrial production of vanilla pods, the flowers are artificially pollinated, and the green fruits are put through a drying and fermenting process that lasts for several weeks. Only in this way can the famous vanilla aroma develop from the primary chemical component, known as vanillin. The complexity of the production process also explains why vanilla pods rank among the world's most eagerly sought after spices.

What do plants need in order to really flourish ?

Plants need water, heat, light and carbon dioxide, as well as up to 15 different nutrients. These include minerals like hydrogen and phosphorus, and trace elements such as iron and zinc. If a single one of these ingredients is missing, a plant will struggle to grow - even if all the other requirements are there in abundance.

How much light do plants need ?

Too little light is fatal for plants. Every kind of plant must receive a certain minimum amount of light in order to survive. If the light level falls below this critical point, the plant starves to death because it is unable to produce sufficient starch. Too much light, on the other hand, can destroy the sensitive membranes responsible for photosynthesis, and consequently the plant itself. This is why plants are equipped with their own molecular solar protection. Specialised carotenoid molecules - which help to add colour to fruits and flowers-transform excess radiation into heat and disperse it by means of evaporation.

How do plants react to pollution ?

Air pollution always places plants under stress, but they do have inbuilt defence systems to protect themselves. If the threat is from ozone, there will be a reaction within a few hours. Pines increase their production of pinosylvin, a substance that under ordinary circumstances protects the trees from fungi and bacteria, while spruces increase their production of catechin, a strong antioxidant. Nevertheless, plants that undergo ozone stress will usually suffer visible damage to tissues, leading to leaf discolouration and leaf drop.

Other harmful chemicals, such as nitrogen oxides in the air, can delay the formation of flowers. When the levels of nitrogen oxides are too high, the plants concentrate on growth rather than flower formation. This often results in too little time being left at the end of the season for the development of healthy fruit and seed.

How do plants and animals survive the chill of winter ?

Living things have developed a range of strategies to help them survive the cold of winter. Many plants shed their leaves for winter and so begin a period of dormancy or rest. Animals, too, have a range of different ways of dealing with winter. Some migrate to warmer climates to escape the cold while others hibernate. For many, however, there is no let-up in the struggle to survive. Life must go on, whatever the weather.

What makes leaves change colour in autumn ?

Before deciduous trees shed their leaves in winter, they first go through a nutrient-recycling process. They draw substances from the leaves back into their trunk and roots, because these are vital to the metabolic processes that take place in trees during the winter months. The most important of these substances is chlorophyll. which contains nitrogen. Nitrogen is especially valuable because soil does not generally contain enough, unless it is added intentionally in the form of fertiliser, as is the case in agriculture. Virtually every part of a plant must have nitrogen for vital tasks such as synthesising proteins and as a building block for nucleic acids. All that is left in the leaves at the end of this process are yellow and red carotenoids. which give them their characteristic autumn colours.

How do animals survive hibernation ?

The vital functions of hibernating animals slow right down when they are dormant during the cold winter months. Their body temperature drops below 10°C, and breathing, heartbeat and blood pressure are all reduced. Taken together, these changes enable animals to save up to 88% of their energy. The small amount of energy that their bodies do require during this period are drawn from fat deposits, which means that hibernators have to eat enormous quantities of food before they can retire to the safety of their burrows or dens to sleep. However, some animals never do wake up from their winter sleep, instead they simply die of cold. If a hibernating creature is woken up too frequently, it will be forced to consume too many of its reserves. This means that it will not have enough energy available to get it through the waking up process in spring, when all vital functions have to be returned to normal levels.

What exactly is a mammal ?

Mammals are a class of vertebrates whose characteristics include the ability to suckle their young with milk and a capacity to maintain a constant body temperature. Palaeontologists believe that the first mammals were small rodent-like creatures that scurried around in the twilight of the Jurassic forests millions of years ago. All of today's mammals are probably descended from those tiny creatures.

Why do camels have humps ?

Contrary to popular belief, camels use their humps to store fat and not water. On long journeys across dry and barren desert regions these cloven-hoofed animals draw sustenance from these reserves of fat. This is why the humps - dromedaries have one and Bactrian camels two-gradually shrink during an enforced diet until they eventually hang down loosely. These mammals have adapted extraordinarily well to life in the desert, having developed mechanisms that enable them to go without water for as long as two to three weeks at a time. Their urine is highly concentrated and their faeces also contain very little fluid. Further more, they can draw moisture from the air with the aid of fine nasal hairs, and are able to reduce the amount of fluid lost through sweating to a minimum thanks to an ability they have to vary their body temperature by as much as 10°C.

When camels finally reach a precious supply of water after a long, thirsty trek, they can drink more than 100 litres in only minutes. Camels are in no danger from hyperhydration - or water poisoning - because their red blood cells are oval-shaped, which prevents them from bursting with such a huge intake of water.

How do bats see in the dark ?

The ability of bats to 'see' in the dark is mainly thanks to their ears. These animals have developed a sophisticated echolocation system, which enables them not only to locate their prey with a high level of precision, but also to avoid obstacles very adroitly. When airborne, these skilled fliers produce sounds with an ultrasonic frequency of more than 20 000 Hz, which are mostly inaudible to the human ear. Echoes of these generally very loud cries are reflected from the bats' surroundings, giving the flying mammals a precise 'sound picture' of their environment. However, bats are not completely blind. They can distinguish between light and darkness and are therefore able to recognise contours. Bats also have a very good memory for places, which they constantly update during the course of their flights.

Why do cats eyes glow in the dark ?

The eyes of cats and other animals that are active after dark are equipped with a special reflective layer of cells - the tapetum lucidum -which lies behind the retina. This layer reflects light rays that are not caught by the eye's photosensitive cells and thus have no immediate effect on the retina. As a result, the light is not immediately lost, but has a second chance to stimulate the eye's photosensitive cells, thereby considerably increasing the overall amount of light received. This is why cats can see so well in the dark. The tapetum lucidum is also the reason why cats' eyes sometimes seem to glow so eerily at night. The glow is a result of light rays passing back through the retina after being reflected in the light-sensitive cells so that it leaves the eyes and can be seen by an observer.

What do we mean by camouflage ?

The word camouflage comes from the French and loosely translated means misinformation or deception. Biologists talk about camouflage when an animal's shape, markings or colouring mean that it can easily be mistaken for another creature or even an object. The animal becomes much harder to spot and may even blend perfectly into its background.

In the wild, these kinds of deception strategies are far more complex than they might appear at first glance. Although camouflage can help to ensure that potential victims are more difficult for predators to spot, it can also aid predators as they attempt to approach their prey unnoticed. Camouflage plays a major part in the survival strategies of both predators and prey as they attempt to outwit their opponents in the struggle to survive.

Why and how do glow worms glow ?

Most glow-worms, fireflies and lightning bugs are actually beetles belonging to the family Lampyridae. They are found in temperate and tropical areas around the world. The larvae of all species glow, which may be a warning to deter predators. Most adults also glow when looking for a mate, and, depending on the species, both sexes may glow, or only the females. Every species produces its own characteristic glow, which avoids mistakes. The signals vary in terms of colour, light impulse frequency and the arrangement of the body's light-emitting organs. The females are often unable to fly and so wait on the ground or in foliage for passing males which they try to attract. Some female fireflies maintain a constant glow throughout the hours of darkness, while others don't begin to glow until they have spotted a glowing male of their own species.

The typical glow - usually greenish-yellow - is produced in the firefly's light-emitting organs, called photophores, by means of a process known as bioluminescence. This is the ability of some living creatures to produce light with the help of biochemical processes. Bioluminescence involves the production of energy by the oxidation of special luminous substances - known as luciferins - which are then transformed into light. This process takes place with the help of an enzyme known as luciferase. Hardly any heat is produced along with the light, which is why it is known as cold luminescence.

How far are butterflies able to travel ?

Some butterflies are able to fly across huge distances. One of the most accomplished travellers is the American monarch, which leaves North America in the autumn and flies to Mexico where it spends the winter. The first three or four generations that hatch during the summer stay in the north where they mate, but the last generation to emerge before the autumn does not become sexually mature, although it will have well developed flying muscles. These butterflies then embark on a long journey, flying more than 3000 km in eight to 12 weeks. The insects travel on average a distance of 70 km per day, but with favourable winds they can cover as much as 300 km or more. They use the position of the Sun for navigation. In the spring, these creatures embark on the return journey north, during which they reach sexual maturity and lay their first eggs. Once they have laid their eggs a lot of females die, as do many males. Their descendants continue a journey that is completed in many stages and often takes several generations.

Can insects help to solve murder mysteries ?

Insects can provide evidence that might be vital in helping to explain a mysterious death. Finding out exactly what the insects might have to tell us is the job of a forensic entomologist, a specialist who analyses the insects that colonise corpses. On the basis of the species that are found and their stage of development it is sometimes possible to pinpoint the time of death and, with luck, the cause or circumstances of a fatality. This is possible because many organisms are involved in the decomposition of dead organic matter, among them fungi, bacteria and, of course, scavenging insects like the maggots of certain flies and beetles. For many flies, a dead body provides more than just a source of food, it is also an ideal breeding place. A corpse is a perfect place to lay eggs since it provides offspring with rich and plentiful nourishment as soon as they have hatched.

Factors such as the location, temperature, humidity and the stage of decomposition can all, to varying degrees, determine which insects will colonise a corpse. This information can be used to give an indication of whether the death actually occurred where the body was found, or whether it had been transported there from somewhere else. Finally, whether only eggs, or larvae or merely empty pupa shells-perhaps from several generations of insects - are found can be used to give a fairly precise indication of the actual time of death.

Human and Animal which is the greater threat to the other ?

People do get killed by animals, but humans represent a far greater threat to other members of the animal kingdom than the reverse. Animals usually appear on lists of endangered species because their numbers have been reduced by hunting and poaching, or because their habitat is so endangered that entire populations are at risk. Compared to the damage inflicted on humans by animals - from bee stings to shark attacks - the damage done to fauna worldwide by humans will have more far reaching consequences for the planet.

Why don't Whales and seals suffer from decompression sickness ?

During a deep dive, the pressure of the water forces nitrogen from the air that is breathed into body tissue. If a diver returns to the surface too quickly, the nitrogen in the tissue forms bubbles which can damage tissue and blood vessels, leading to mental confusion, severe pain, internal bleeding, paralysis and, in extreme cases, death from decompression sickness (known as 'the bends'). Whales, dolphins and seals, on the other hand, encounter few problems when they surface from great depths. This is because, unlike divers, they don't continue to breathe underwater. They have a thorax that is very flexible and which is gradually compressed as the pressure increases, thereby causing the contents of the lungs to be gradually squeezed out. This apparent collapse of the lungs does no damage to these aquatic mammals. Instead it provides a very effective protection against decompression sickness.

How do dolphins sleep ?

Biologists observing both wild and captive dolphins have noticed that they swim around in circles when they are asleep. They can do this because only one-half of their brain actually sleeps at any one time. Researchers suspect that this behaviour serves to keep individual members of a group together. When dolphins are awake, they communicate by making whistling sounds which enable them to find one another easily. But when they are asleep, such sounds could easily draw unwanted attention from predators. However, if all the members of a group swim steadily and silently around in circles, they can still stay together but without attracting uninvited visitors.

Do whales and dolphins have 'fingerprints' ?

In principle the answer has to be yes, although, of course, whales do not have fingers, and therefore do not have individual line patterns on their skin. Instead, what counts as the equivalent to a fingerprint in the case of these aquatic mammals is the shape of the fins, which are almost as unique and recognisable as human fingerprints.

Most distinctive of all are the notches along the edge of the fins, which vary significantly from one individual to another. These patterns seem to change very little over time - barring accidents and misadventure - and can therefore assist biologists in identifying particular animals in the wild. Whales are most recognisable by their tail fins, dolphins by their dorsal fins.

Why do whales sing ?

So far, biologists have not been able to explain with any degree of certainty why whales 'sing'. It is thought that the sounds they make are primarily for communication, but they also seem to contribute to a whale's development and wellbeing.

Researchers speak of whale 'song' because these giants of the sea make sound patterns that are regular and predictable. Male humpback whales, for example, only produce certain sequences of sounds during the mating season, presumably because this special song plays a central role in finding a mate. It is still unclear, however, whether this display is aimed at females or potential male rivals. Humpback whales also use individual sounds that are not part of complex songs to mark out their territory or when hunting in groups.

How are amphibians and reptiles different ?

Amphibians grow up in water and adults can survive either on land or in water, although they need to keep their skin moist to avoid drying out. Reptiles are much better adapted to living on land since they are equipped with a hard, very horny, waterproof skin. They also lay waterproof eggs, which give the embryo greater protection and can be laid almost anywhere.

How do snakes climb tree trunks ? 

Snakes move by using their muscles, sinews and scales. Land snakes have very wide, flat scales along their stomachs which are directly connected to their ribs via several muscles. When a snake moves along the ground these scales are splayed out so that they can hook onto uneven surfaces. The snake can then push and pull itself forward, sometimes achieving speeds of 15 km/h. Exactly the same mechanism is used when snakes climb trees, even vertical ones.

How do geckos run up smooth surfaces ?

Geckos have amazing abilities. They can run up smooth glass surfaces or dangle upside down by one leg from the ceiling without any problem. They can perform these feats thanks to the special pads on the undersides of their toes. These are covered in millions of microscopic hairs, and each one branches out into thousands of tiny bulges. As a result, the hairs can be brought into very close contact with a surface so that they stick due to the weak electrostatic force, known as the Van der Waals force. The adhesive strength of an individual bulge is extremely weak, but with several billion bulges, a gecko is able to achieve its extraordinary clinging power. Using all four feet, a gecko can support a weight of about 140 kg.

How did the dinosaurs live ?

Dinosaurs lived on the land, in water and in the air. On land there were so many dinosaurs of different kinds that they covered many ecological niches. They ranged from creatures the size of chickens to sauropods more than 30 m long-the largest land animals ever to have lived. Most dinosaurs were probably cold blooded, although there is evidence that some were warm-blooded or that they developed hybrid temperature regulating systems. Nearly all were fast, energy-efficient runners, since their legs were positioned beneath their bodies rather than at the sides. The largest of the water-dwelling dinosaurs, known as ichthyosaurs, grew to lengths greater than 15 m.

Why is the underwater world so colourful ?

Colours are used by the inhabitants of coral reefs in much the same way they are by land dwellers. They act as signals, assist in helping to find a mate, provide camouflage and send out warning messages. At depths of greater than 200 m everything looks black to us, but not to reef fish. Many have colour receptor cells in their eyes and are able to detect ultraviolet light, which penetrates further into the depths than visible light.

Are fish deaf and dumb ? 

Fish are anything but dumb. Squirrelfish communicate with clicking sounds, wrasse grunt, gurnards growl and male drumfish have special muscles around their air bladder which produce a drumming sound when contracted rapidly. Most remarkable of all, when herrings fart it has nothing to do with their digestion, but everything to do with communication. In order to have a conversation they swallow air which they expel through the anal orifice in their gas bladder. In this way the fish can produce notes extending over more than three octaves at frequencies of between 1.7 and 22 kHz. They can hold each note for almost eight seconds.

Since fish can make such a range of noises, it seems only logical to assume that they can also hear. They do so through their inner ear which is connected to the air bladder by what is known as the Weberian apparatus, which functions as the eardrum in the process of hearing. The Weberian apparatus then transmits the sound to the inner ear - in a similar fashion to the way the auditory ossicles function in mammals.

What do fish need to survive ?

Although fish live in water, like all other animals they need one thing above all else - oxygen. Without it, they would suffocate in a matter of minutes. This is why water quality is important. From the point of view of a fish, healthy water contains sufficient oxygen, is low in toxins and harmful substances, and should have about the same level of acidity as drinking water. Some fish are herbivores, but many need animal matter as food, which is why zooplankton - tiny creatures like water fleas and minute crustaceans that feed on microscopic plants forms the basic diet of many types of fish. Because aquatic life is just as varied as life on land, there are fish with widely differing needs, depending on their local ecosystem and the kind of waters they live in.

Can we distinguish individual fish by the way they swim ?

Observations of goldfish have shown that each individual has its own swimming style. The likelihood that two goldfish will go through the same sequences of movement is almost zero, so each will execute turns or changes of speed in its own characteristic way.

Why do dead fish float upside down ?

Like all living creatures, gases build up inside a fish's body when it dies, and this keeps it afloat in the water. These gases collect mainly in the abdominal cavity, which is on the underside of the fish. When this happens. the lighter, gas-filled abdomen becomes buoyant and the more compact back forms the centre of gravity, with the result that the fish is turned upside down. It is only when decomposition is further advanced that the gases are released, and the fish sinks.

What makes bird so special ?

Birds developed from reptiles and are closely related to the extinct dinosaurs. They are the only class of vertebrates of which almost all of the members have conquered the skies. Most birds are able to fly and their bodies are adapted to this way of life. Their frontal appendages have developed into wings, and their bones are hollow - which keeps them light while at the same time strong enough to withstand the stresses of flight. Birds also have a respiratory system that is proportionally larger than that of the average mammal.

Why do parrots speak ?

Parrots don't actually speak, they merely imitate the sounds they hear. This could be human speech, an alarm clock, other birds or the telephone. In their natural habitat, parrots generally live in large groups. In captivity and deprived of their usual company, this social instinct drives parrots to mimic human language in order to forge a relationship with the human beings who have become their replacement companions. In birds, the air flow required for speaking or singing is produced in the syrinx. The bird uses its tongue to form various sounds and even the smallest change of position is enough to produce a completely different sound.

Do songbirds have perfect pitch ?

Songbirds do indeed have perfect pitch. A scientific study has shown that various songbirds, including zebra finches and white-throated sparrows, are much better at determining, distinguishing and remembering isolated pitches than human beings or rats. Even when human subjects were provided with a second sound for comparison, they were far less skilled at determining its pitch than songbirds. Hardly surprisingly, rats appear to find this kind of test very difficult.

What it is that causes the differences in hearing ability has not yet been thoroughly researched. The company of conspecifics seems to play a role in the development of hearing in birds, since birds reared in isolation seem to do less well in experiments of this kind. Early experiences with music play a role in human beings. Most babies have perfect pitch, and this is usually preserved if they are given music lessons at an early age. Speaking a tonal language such as Mandarin - where words can have different meanings depending on tone and pitch - also help to develop perfect pitch.

How does bird vission differ from that of humans ?

On most birds, the eyes are arranged on the sides of the head, which is why they can see a large portion of their surroundings at any one time. Indeed, the woodcock's eyes are so far apart that they have 360° vision. The drawback with having eyes positioned far apart is that the area that is seen by both eyes simultaneously-something that is necessary if a creature is to have binocular vision - ends up being relatively small. The birds have to compensate for this by continuously moving their heads from side to side. This results in enough separate visual information being received by each eye for the brain to be able to use it to construct an integrated, three-dimensional image.

Many birds also have very large eyes, which gives them good vision even in dim light, and there are a large number of birds that are able to see ultraviolet light in addition to the usual colours. This can be of benefit both for finding food and a partner.

How do migrating birds find their way ?

Migratory birds seem to know instinctively when it is time to move on and where it is they need to go. They are guided on their journey by the position of the Sun during the day and the stars by night, and they can also make use of the Earth's magnetic field for navigation. However, the exact details of the process, the precise nature of the sensory organs used, how the mechanism as a whole works and where it is located in the body continues to be a puzzle.

It seems certain that the sense organ that allows the birds to orient themselves magnetically is located somewhere in their heads. Before they fly off they can be seen determining where north is by moving their heads to and fro many times. This is probably how they find the position of the magnetic field, and it is thought that special receptors or molecules that undergo chemical changes when in contact with magnetic fields are probably involved. These receptors may be located in the retinas of birds' eyes, and among possible candidates are the chryptochromes, which are found in particularly high concentrations there.

How do pigeons find their way home ?

Scientists still don't really know how pigeons find their way around. However, there are indications that, like migratory birds, they are guided by the Earth's magnetic field and the position of the Sun and stars. Pigeons have small magnetic particles in their heads which they use to locate the Earth's magnetic field.

Studies have shown that pigeons will also rely on visual clues when they are flying home, using prominent traffic arteries such as motorways, railway tracks and main roads to orient themselves. When they have settled on the correct direction to reach home, they will often fly along a major traffic artery that is going in more or less the right direction. They will even keep following the course taken by an artery when it is not following the most direct route.

Why don't penguins stick to the ice ?

Although it has a body temperature of 39°C, a penguin's feet are always cold. While that may sound uncomfortable to us, it is thanks to this adaptation that the birds can stand on an icy surface without it thawing, and since no liquid water is formed, their feet do not stick to the ice. To ensure that the feet always stay cold, the flow of blood is restricted. Veins and arteries in the legs are surrounded by muscles that are able to contract so that the blood supply is kept to the minimum necessary to maintain the temperature of the feet at just above 0°C. Since this also cools the blood, it is necessary to ensure that it is not too cold when it returns to the body. It is therefore directed through numerous small blood vessels and past warm arteries, becoming warmer as a result.

Why do emperor penguins keep their eggs on their feet ?

Most penguins build nests for their eggs and chicks, but emperor and king penguins do not. Instead, they use their bodies to protect the eggs and keep them warm, placing them on their feet to do so and using a fold of skin as a covering. They have adopted this strategy because there isn't sufficient nest building material in the areas where these birds breed. Emperor penguins breed on the pack-ice so the best and only protection for the eggs is balanced on their parents' feet. In this way emperor penguins are even able to hatch their chicks in the polar winter, when temperatures fall as low as -40°C. Once hatched, the chick is also transported around on their parents' feet, still protected by the fold of skin.

How do insects see the world ?

Insects have a completely different view of the world to ours. Firstly, they are very much smaller, which means that, from a subjective point of view, their surroundings are much enlarged. Secondly, many insects are able to fly, and this gives them a broader overview. Finally, while we see our environment as a single image, insects see it through compound eyes and therefore their view is likely to be a mosaic made up of numerous individual images.

Why are insects so small ?

If the air contained more oxygen, insects could be much larger than they are now. It is the amount of oxygen that determines how effective the invertebrate trachea is. This labyrinthine system of tubes runs throughout an insect's entire body and supplies it with oxygen. As a result, the larger the insect, the larger and more complicated its oxygen supply system has to be. This places a limit on the size of insects, but an increase in the oxygen content of the atmosphere would allow the system to function more effectively. During the Palaeozoic era, when the oxygen content of the air was 35% compared to today's 21%, dragonflies were able to exist that had a wingspan of 760 mm. However, there is another factor that places an upper limit on the size of insects. At the point where limbs and body meet, the trachea can only be as thick as the delicate structure of the joints permit. As a result, once a certain size is reached the extremities can no longer be supplied with sufficient oxygen.

What is the best way to rid yourself of troublesome insects ?

The trusty old fly swat is not the only way to deal with annoying insect guests. The pest control industry has provided a vast variety of options for combatting irritating pests such as flies, ants, moths and mosquitoes. We can choose anything from sticky fly paper and elaborate traps to natural pest control substances and the insect equivalent of chemical warfare agents. Not all methods are equally effective, however.

How do social insects organise their colonies ?

The central principle around which communities of social insects ants, bees, wasps and termites are organised is the division of labour. Supplying and protecting the nest, care of the young and reproduction are organised in such a way that no individual performs all the tasks that need to be done if the community is to thrive. Among bees, the workers are responsible for the everyday jobs like providing food and looking after the young while among ants the soldiers take care of defence, never considering their own lives in a fight to protect the nest. Since they are infertile, workers and soldiers must rely on others to replenish the population. In most communities it is the queen that is responsible for producing the offspring, and she only mates with a few select males.

Ants have particularly complex societies, and will even 'farm crops' and 'keep livestock. Some species feed and protect aphids and caterpillars which they milk for the sweet secretions, while others grow a special fungus which is used to feed the entire colony.

FOCUS

Economically useful plants and genetic engineering

Ever since human beings gave up being nomads, they have tried to adapt plants to meet their needs. Targeted breeding has increased yields, reduced susceptibility to disease and produced new varieties. Genetic engineering is now opening up a range of completely new possibilities, such as the production of transgenic plants - plants that have the genetic material from other organisms inside them.

The story of so-called 'Golden rice' is a good example of the pitfalls and potential of this brave new world of transgenic plants. This new rice variety was developed to contain two foreign genes - one from the wild daffodil and another from a bacterium and seemed to be a development that promised a great deal. The modifications were designed to make the plant produce beta-carotene, a precursor of vitamin A, in its seeds. It was thought that people living in Asia's developing countries would benefit because their predominantly rice-based diets meant there was widespread vitamin A deficiency. Things didn't turn out as planned, however. Some of the rice suffered growth disorders, and the vitamin content was so low that a daily intake of up to 2 kg of rice would have been required for there to be any benefit to consumers. Despite the setbacks, scientists haven't give up on the idea, and foresee a time when rice that contains iron, zinc and vitamin E, as well as vitamin A, is widely available.

Another transgenic plant experiment that attracted considerable attention was a cross between a tomato and a potato. To create it, researchers fused together individual cells known as protoplasts. These new cells contained the genomes for both species, and a hybrid developed that produced tomatoes above ground and potatoes below ground. Such a combination would never have occurred naturally.

What happened to the tomato-potato hybrid?

Unfortunately, the tomato-potato hybrid was another failure. The potato yield was meagre and the plant as a whole was unstable. It failed to produce fruits or seeds and was therefore incapable of reproducing When cells from two different species are merged, the result may be a new strain, but a few genes always get lost in the process, something that is very difficult to control.

In addition to the technical problems, the reaction of consumers to the new plant was not positive, and it has not been alone in attracting a negative response. Many people have doubts about any genetic modification, even if only genes belonging to an individual plant are modified, or only single foreign genes are added.

Why doesn't anyone want tomatoes that don't go squishy?

A tomato was developed in the mid-1990s that didn't go squishy. One of the tomato's own genes-the one that produces the enzyme polygalacturonase-was altered in order to achieve this. This enzyme starts to dissolve the cell walls within a tomato as soon as it ripens, making the skin softer and less robust, which in turn causes the fruit to become squishy. The plant benefits from the softer skin because this helps it to release its seeds. But, from a grower's point of view, tomatoes keep longer without the enzyme, with ripe, non-squishy tomatoes remaining edible for up to eight weeks. Despite its apparent advantages, the non-squishy tomato wasn't popular among European consumers. The verdict was that it lacked flavour, although it is possible that the idea of eating a genetically modified tomato spoiled the fruit's appeal.

Can plants produce medicines and vaccines?

Plants have always played an important role in medicine, and transgenic plants seem set to expand the possibilities. By adding a gene, it is hoped that it may be possible to produce vaccines, antibodies, hormones and proteins. Manufacturing these substances with the help of a growing plant would be much cheaper than producing medicines by using animals or cell cultures. Thanks to the so called 'gene gun' - a machine that shoots tiny particles of gold or tungsten carrying the required genes into plant cells - it is now possible to add foreign genes to almost any plant. Another technique uses a bacterium to introduce foreign genes into plant cells. As early as 1986, the first pharmaceutical tobacco plant was producing human-growth hormones. Today, more than 80 different medicines made using genetically modified plants are marketed worldwide.

Are synthetic plants a possibility? As well as trying to improve existing plants, scientists have been working on producing synthetic plants that would catch light and use it to turn the carbon dioxide in the air into glucose or other compounds, just as happens in the membranes of plant cells. Researchers have so far had some success using a mixture of organic materials, photo sensitive molecules and semiconductors to generate small amounts of energy and produce methane, a gas that can also be used as an alternative source of energy.

New foods, medicines and energy sources already exist, and the possibilities seem limitless. However, there is widespread scepticism among consumers, who will ultimately decide on the technology's fate.

How do animals and plants survive in extreme conditions ?

Our planet offers a range of habitats, some of which look very uninviting. Nonetheless, few habitats - however extreme - seem to be sufficiently hostile to prevent some plant or animal from living in them. Fish live in the inky blackness of the deepest seas, penguins and polar bears have conquered the polar wastes, cacti bloom in the desert and salt-loving halophytes flourish in soils that would kill other plants.

How is it possible for plants to grow in soil with an extremely high salt content?

Ordinary plants cannot survive in really salty soil because the salts seriously interfere with their ability to absorb nutrients and water. However, there are plants - known as halophytes - that have specialised in surviving in precisely these kinds of habitats, where they enjoy the advantage of not having to deal with competition. With the exception of the polar regions, halophytes are found in many different habitats around the world - from the seaside to salt steppes, the margins of salt lakes and springs and even tropical rainforests. Some halophytes actually need salt and would fail to flourish in ordinary soils, while others would probably fare better in conventional soil, but are also able to grow in a salty medium. Halophytes adopt various strategies to deal with the salt. Some species prevent salt from entering their roots, letting through only those salts required by their metabolism and blocking out the rest. Others actively excrete potentially damaging salts through special glands or hairs, while some species have mechanisms in their cells which prevent the salt from reaching concentrations that might result in damage to the plant.

Are there any plants growing on the Antarctic continent?

Plants have been discovered growing in the extreme climate to be found in Antarctica. The vegetation is not exactly rich in species, but some lichens, mosses and grasses have gained a foothold there. The local soil is low in nutrients, so most Antarctic vegetation grows in the vicinity of bird colonies. There is one more highly developed plant that has succeeded in overcoming the cold - the Kerguelen cabbage, which grows on several islands close to Antarctica. Most Antarctic plants grow in clumps just above the ground, where they present the smallest possible target for wind and weather. In addition, they are very robust and boast an amazing capacity for regeneration.

Why is it that there are plants which can flourish in the desert?

Although deserts are characterised in part by a lack of vegetation, there are a number of cactuses, grasses, bushes and even trees that have adapted to the inhospitable conditions. These plants - known as xerophytes - are experts in survival. They need very little water and have developed a variety of ways of collecting what little there is and surviving on it. Cactuses, for example, can store water for several months, while some small herbaceous plants have developed extensive root systems that branch out over a wide area just below the surface of the ground, helping them maximise their water intake. Most types of desert trees adopt the opposite strategy, with very deep roots that reach down to the water table. In very long droughts, some trees shed their leaves to avoid losing what little water they have through evaporation.

How do animals cope with the extremes of heat and cold?

Not only plants, but animals as well have managed to adapt to extreme conditions. Desert reptiles and small mammals like jirds and jerboas can manage with just the fluid contained in their food. They can also retain water for very long periods of time and use it sparingly, with barely any water being wasted in their urine and faeces.

The icy wastes have also been tamed, with mammals native to these regions growing a layer of insulating fur to protect themselves from the cold. In addition, sheer size can also offer protection against freezing temperatures. It's basic physics that as a sphere becomes bigger, the surface area/volume ratio decreases. The same holds true for animals, so that as a creature increases in overall size the surface area of its body - across which it can lose heat increases at a smaller rate than its internal volume, within which it can retain heat. As a result, bulky creatures lose heat more slowly than smaller ones. According to the principle Bergmann's Rule, this is why many animal species tend to be larger the closer they live to the poles. Penguins are an example: the biggest survive closest to Antarctica.

Animals that live in cold regions also tend to have relatively small extremities and appendages, such as ears and tails. Too much heat would be lost through large extremities and they could also easily become frostbitten. This is why the Arctic fox has very small ears. At the other end of the scale, animals in the hotter parts of the world have large appendages that tend to stick out. This increases the surface area across which they can lose heat and helps prevent the body from overheating. Unlike its relative in the Arctic, the desert fox has ears that may look almost absurdly large to us, but they are perfectly adapted for the task of radiating excess heat.

Why does the polar bear have black skin under its white fur?

A thick layer of insulating fur is one of the most important ways in which mammals keep warm in freezing temperatures, and the polar bear has developed a particularly sophisticated system. The hairs of its coat are hollow and provide extremely good heat insulation, since air is a particularly good insulator. The polar bear's fur may appear white or yellowish, but in fact each individual hair is transparent, which allows the Sun's rays to reach the bear's black skin where the heat is absorbed very efficiently due to the skin's dark colour. At one time, it was believed that the hairs worked like glass fibres, helping to direct light and heat to the animal's skin. Since then, however, the hairs have been found to be less efficient light conductors than was believed. Nevertheless, the polar bear's coat is extremely effective. and the hollow hairs also provide buoyancy.

Evolution - theories and facts

In the mid-19th century, Charles Darwin shook the world with his theory of evolution. He suggested that all living things are descended from common ancestors and that over the course of time they develop by a process of natural selection which brings about constant change. This seriously challenged the idea of a God who created every single species. While some greeted Darwin's theory enthusiastically, it also met with widespread scepticism and remains controversial to this day. Although Darwin produced plenty of evidence to support his theory, it did not amount to proof in the eyes of many of his critics. Since Darwin's time, however, scientists have amassed a lot of evidence in support of the evolutionary mechanisms proposed by Darwin. Findings in the field of molecular biology - Darwin knew nothing about genes - clearly show how evolutionary processes are based on genotype mutation, selection and heredity.

Was Darwin the first to develop a theory of evolution?

Darwin was not the first to wonder about the diversity of organisms. The French naturalist Jean Baptiste de Lamarck suggested that species changed over time 50 years before Darwin published his Origin of Species in 1859. Lamarck also gave thought to the mechanisms behind these processes, suggesting that features and characteristics survived solely through use. He maintained, for example, that giraffes had long necks because they were constantly reaching up for leaves, and this acquired characteristic was passed on to succeeding generations. Unlike Darwin, Lamarck did not hit upon the principle of random variability and natural selection, by means of which only the better adapted survive. Some characteristics that result from chance alterations to the genome prove useful and are retained, while others which confer no advantage are lost.

Darwin was influenced during his early career by Lamarck's work. However, by the time he began writing the seminal Origin of Species he had disregarded virtually all of the French naturalist's theories. Working at around the same time as Darwin, the naturalist Alfred Russel Wallace also formulated a theory of evolution, which in many respects coincided with Darwin's. The two scientists kept up a correspondence, but each developed his own theory independently. Darwin was able to support his theoretical observations with the extensive evidence collected on his travels, which was something Wallace could not do.

Are mammals former reptiles?

Darwin's theory turned the contemporary view of the world upside down. Suddenly. human beings were no longer God's supreme creation, but instead they shared a common ancestry with the apes. To many, this was too much to accept, but today most people are more comfortable with the idea.

We now know that all mammals are descended from reptiles, their direct forebears being the vertebrate group known as the synapsids. Later forms of these reptiles displayed typically mammalian characteris tics. Their metabolism was faster than that of reptiles and they were therefore warm rather than cold-blooded. Their skin was already partly covered by hair and their teeth included incisors, canines and molars. Moreover, unlike reptiles, their legs did not grow out of the sides of their bodies but were situated beneath their bodies. Of the synapsids, it was the therapsids that became more and more similar to mammals and it is thought that all of today's mammals are descended from them.

Do some animals never grow up? 

Over the course of millions of years, evolution has been responsible for producing the huge diversity of life- both plant and animal we see around us. It has also produced some very strange results, such as the ani mals that never grow up. Some salamanders spend their entire lives as larvae, yet still reach full sexual maturity. They retain their gills and stay in the water, rather than ven turing onto land as most adult amphibians usually do. Among this group are the Euro pean olm and the axolotl.

Can single-celled organisms see?

 The eye is an organ that has been used by both the advocates and the opponents of evolutionary theory to support their case. Darwin himself had doubts about his theory when he considered the eye's extremely complex structure. The fact is, however, that the eye can be a great help when it comes to understanding how evolution works. Even single-celled organisms like euglenas and many of the dinoflagellates have the sense of sight, and this can sometimes be extremely complex. For example, the dinoflagellate Erythropsis pavillardi contains most of the components that make up a vertebrate eye. These include a lens, a retina-like structure and an opaque spot of pigment that shields against light from one side. A similar structure also enables euglenas to move towards a light source. The first fossilised evidence of eyes is found in fossils about 540 million years old. This is when the evolution of the eye began, and all the eyes we know today developed within a period of a mere 100 million years.

Can apes see in colour?

Not only sight itself, but also the ability to see colours is an example of continuing development during the process of evolu tion. The first reptile like mammals proba bly lived in semi-darkness and so had little need of an ability to recognise colours. As a result, their visual sense deteriorated and most of their descendants have at most two different types of sensory cells - known as cones - which are responsible for colour vision. However, certain primates - including humans - are among the few mammals with three types of cones in their retinas, a feature that results in much better colour vision. Creatures with the three types of cones can distinguish between red and green, which is a distinct advantage when life is lived mostly in bright daylight, a fact that helps to explain why this ability has been retained.

Fast, higher, farther - records from the animal kingdom

Many of the physical things human beings are able to do only with the help of technology, some animals can achieve unaided. There are a number of animals that can run faster than any Olympic sprinter, while others can easily maintain speeds through the water that human world-record-breaking swimmers can only dream about. In any contest between humans and the rest of the animal kingdom, humans would be the losers.

Which is the slowest moving mammal?

Representatives of the three toed sloth family - which are natives of South America - move at a speed of 0.16 km/h across the ground. What's more, they have great difficulty in achieving even that leisurely speed. How ever, when travelling in the branches of the trees where they have their actual habitat, these creatures become a bit more mobile and have been known to achieve speeds as high as 0.27 km/h.

Which is the fastest animal on land?

The cheetah holds the sprint record. This agile predator is able to achieve speeds of almost 120 km/h over short distances. Over long distances, however, the cheetah must defer to the pronghorn antelope, which can sustain speeds of about 88 km/h.

Which is the fastest animal of all?

On average, a diving peregrine falcon will reach speeds of around 350 km/h. The fastest dive recorded so far reached a stunning 389 km/h.

Which animals are the fastest swimmers?

With a top speed of 111 km/h, the sailfish is the fastest swimming fish. The fastest swimming marine mammal is the orca or killer whale, which can reach speeds of up to 55 km/hr. Even the Gentoo penguin is no slouch in the water, reaching a record for aquatic birds of 27 km/h.

Which animal jumps the farthest?

The record in this category is held by one of the smallest contenders - the flea. World champions at the long jump, these tiny insects can cover 200 times their own body length with just one leap.

Which is the heaviest land mammal?

An average male African elephant grows to a height of about 3 to 3.7 m and weighs between 4 and 7 tonnes, which makes it the heaviest land mammal. Some fully mature elephant bulls can even reach a height of 4.9 m and a weight in excess of 7 tonnes.

Which is the tallest land mammal?

This record is held by the giraffe, with males growing to a height of about 5.5 m. Like most mammals, these long necked residents of the African savannah have just seven cervical vertebrae - in their case, however, each vertebra is much enlarged.

Which is the longest and heaviest snake?

Two species- the green anaconda and the reticulated python-compete for the world record in this category. The anaconda, which reaches a maximum length of between 8 and 9 m, does not grow to be any longer than the reticulated python, which in rare cases can grow up to 10 m. However, with a weight of more than 200 kg, the anaconda is considerably bulkier than its rival, making it the world's largest and heaviest snake.

Which is the largest marine animal?

The blue whale grows to an average length of 27 m and can weigh up to 150 tonnes. This makes it the largest mammal ever to have lived on the planet. The record holder is a specimen that was caught in waters around Antarctica in 1947. This massive female was 33 m long and weighed 190 tonnes.

Which was the largest of the dinosaurs?

For a long time, the vegetarian Brachiosaurus, which weighed about 70 tonnes and grew to a height of 13 m and a length of 25 m, was thought to have been the largest dinosaur. However, recent fossil finds seem to indicate that much larger dinosaurs may once have existed. The Argentinosaurus, the Seismosaurus and the Supersaurus may have grown to lengths of about 40 m, which means they would have been considerably larger than the former record holder. However, so far no com plete skeleton of these giants has been found.

Which were the largest insects?

With a wingspan that could reach 700 mm, the largest insects ever to have lived are thought to have been the Meganeura, which resembled huge dragonflies. These giant insects first appeared on Earth around 320 million years ago and became extinct 70 million years later.

Which is the smallest mammal?

The bumblebee bat - also known as Kitti's hog-nosed bat- and the Etruscan shrew jointly hold the record for being the world's tiniest mammals. The bat measures between 29 and 33 mm from head to rump, has a wingspan of about 130 to 150 mm and weighs no more than 2 g. The Etruscan shrew is 30 to 35 mm long from head to rump, has a 25- to 30-mm-long tail and weighs about 2 g.

How large are the largest molluscs?

Capable of achieving a length of 17 m and a weight of around 900 kg, the giant squid Architeuthis dux is both the largest known mollusc and the largest invertebrate. The biggest bivalve mollusc is the giant clam Tridacna gigas, which can grow to a weight of about 200 kg, with a 1.5-m-long shell.

Which animals live the longest?

Sponges of the species Scolymastra joubini may have been alive for an astonishing 10 000 years or more. Scientists have calculated the age of these sedentary sea creatures based on their present size, given their extremely low oxygen consumption and very slow metabolism. Specimens of these giant sponges - which live in Antarctic waters - have been measured at 2 m in height with a diameter of up to 1.7 m.

Which is the strongest of the animals?

The record holder in this category is the rhinoceros beetle. These sturdy insects can carry loads of up to 850 times their own weight.

What insects form the largest swarms?

The largest swarms are formed by the desert locust. In 1954 a locust swarm in Kenya covered an area of about 200 sq km. The enormous cloud of insects was thought to contain 50 million individuals per square kilometre, which means that the entire swarm was probably made up of about 10 billion insects.

Which is the noisiest insect?

Of all the insects, the African cicadas produce the loudest noise. At a distance of 500 mm, their chirping can reach a level of 106.7 decibels-louder than a chainsaw. The song of a cicada plays an important role in communication, helping it to find a mate and possibly in defending its territory against intruders.

Which animal is the fussiest eater?

The most pernickety animal when it comes to food has to be the koala. It eats almost nothing but eucalyptus leaves, as well as the tree's bark and fruits. Furthermore, this fussy eater will only snack on about 70- but in some cases only five or so- of the approximately 700 species of eucalyptus that grow in Australia. Koalas will search through several kilograms of leaves every day in order to eat just 500 g. They specifically look for older leaves, since these contain fewer toxins than young leaves.

Which birds fly the highest?

The highest altitude at which a bird has been observed flying is 11 300 m. In late November 1973. a Rüppell's vulture collided with a commercial aircraft at that altitude over Côte d'Ivoire,

Which are the loudest animals?

The loudest animal noises of all are emitted by blue whales and finback whales. The low frequency sounds they emit reach a sound level of 188 decibels.