Temperate woodlands and grasslands

TEMPERATE
WOODLANDS AND
GRASSLANDS

Across the Northern Hemisphere the temperate woodlands and grasslands form a broad belt encircling the globe, interrupted only by high mountains and seas. South of the equator temperate habitats are found only in isolated pockets.

Temperate woodlands and grasslands are characteristic of middle latitude areas, where warm sub-tropical and cool sub-polar air masses meet. This boundary is not fixed but moves north and south with the seasons and varies a great deal according to the geography and relief of the region. In the lower temperate latitudes, the western edges of the continents tend to have hot, dry summers and mild, damp winters, while the eastern edges are warm and humid all the year round with frequent summer thunderstorms. In higher latitudes the cool sub-polar air masses are the more dominant influence and the general eastward movement of the air brings rain to the western margins, giving damp, humid conditions in both summer and winter.
The typical vegetation in humid areas is deciduous forest, but, in places where the rainfall is high and there is little difference between summer and winter temperatures, evergreen forests of both coniferous and broadleaved trees are found. Most of the tree species present are influenced by soil type and local relief. Pines are found on gravelly soils and rock outcrops, and alders and willows on waterlogged soil by rivers and streams - but the main types of tree are oak, ash, maple and beech. The characteristic feature of deciduous woodland is the difference between its summer and winter aspects. In the summer the leaves form an almost continuous canopy and little direct sunlight reaches the ground. After the annual shedding of leaves the trees stand stark and naked against the wintry skies and the inhabitants are faced with new conditions of lighting and cover as well as of temperature and precipitation.
They react to this in many ways, including hibernation and migration. The discarded leaf matter forms a thick, rich soil and contains three sources of plant nutrients - rotting plant material, humus and clay minerals. The humus slowly releases nutrients into the soil and also traps essential minerals such as nitrates and phosphates. The clay minerals store potassium, sodium and calcium - important raw materials necessary for photosynthesis.
In areas of seasonal rainfall where the total precipitation is between 25 and 75 centimetres, grass forms the dominant vegetation. Although all grassland areas have an annual period of drought lasting several weeks or months when the surface soil dries out completely, their fundamental characteristic is the total absence of moisture at depth in the soil. The lack of water at this level does not impede the growth of grass, which is shallow rooted, but prevents trees, which have deep roots, from establishing themselves.
The temperate woodlands and grasslands probably represent the habitats that suffered most during the Age of Man some 50 million years ago. Man cut down the forests to supply fuel and to provide space for agriculture and settlement. He ploughed large tracts of grassland to plant cereals and created wide expanses of pasture land for grazing animals. These disturbed areas did not revert to their natural state until a long time after man's disappearance. This interference caused the extinction of a great number of animal genera native to the original habitats. However, some creatures did survive, and it was from these that the animals of today's temperate woodland areas are descended.


THE RABBUCKS

The evolution of the major group of herbivorous animals

Several species of hopping rabbuck, Macrolagus spp., still survive. This evolutionary older group consists largely of woodland animals that feed on the leaves and shoots of trees.

 

 

The hopping rabbuck moves in a bounding motion (a, b, c, d) reminiscent of its rabbit ancestors, whereas the running form, Ungulagus spp., moves in a manner similar to that of the ancient deer (e, f, g, h).

The hopping rabbuck

rabbit hopping rabbuck running rabbuck

The development of the foot from the large springboard structure of the rabbit to the light, two-toed hoof of the rabbuck was crucial to its evolution. The three principal stages are shown here, although not to scale.

 

 

 

The running rabbuck

During the period immediately before and during the Age of Man the principal large-scale grazers and browsers were the ungulates, the hoofed mammals. They were generally lightly built running animals, able to escape quickly from predators and with teeth particularly suited to cropping leaves and grasses. The ungulates were widely used by man for his own purposes. Cows and goats were domesticated for milk and meat, sheep were bred for wool and the skins of many were used for leather. Horses and oxen were harnessed to work for man and became the classic beasts of burden. By the time man became extinct these animals had become so dependent on him that they could no longer survive.
The deer, the wild ungulates of the temperate latitudes, fared little better. Vast tracts of temperate woodlands had been destroyed to make room for man's cities and to provide agricultural land. This interference with their habitat was so intolerable and put such pressure on the deer that their numbers fell to a level from which they never recovered. What then could take their place? A whole ecological niche was vacant with nothing to exploit it. Which creature was best placed to take the initiative?
During the Age of Man a small-scale grazer was present that was so successful it was considered to be a pest. The rabbit was so seriously destructive of man's crops, that man made numerous attempts to control it and even attempted to exterminate it. Yet no matter what actions he took he never succeeded in getting rid of it completely. After man's disappearance, the rabbit's versatility and short breeding cycle enabled it to develop successfully into a number of separate forms. The most successful, the rabbuck, Ungulagus spp., now occupies the niche left by the ungulates.
To begin with the rabbuck changed little from its rabbit ancestors excepting for size. In an environment totally devoid of large, hoofed grazing animals the rabbit was left with no major grazing competitors and quickly evolved to occupy the position they once held. The early rabbucks, Macrolagus spp., retained the hopping gait of their forebears and developed strong hind legs for leaping. However, although jumping was ideal for moving around the open grasslands, their traditional habitat, it was not the best method for the confined spaces of the forest, and a more fundamental change had to take place. Several species of this earlier line still exist, but their place has largely been taken by the running forms of rabbuck that more closely resemble the deer of earlier times.
The second major development took place some ten million years after the Age of Man. As well as developing rapidly into the size of a deer the rabbucks also began to evolve the typical deer leg and gait. The jumping hind limbs and the generalized forelimbs of the rabbit grew into long-shanked running legs and the feet changed radically. The outer digits atrophied and the second and third toes grew into hoofs, strong enough to bear the animal's weight. This was a highly satisfactory arrangement and this line has now largely replaced the leaping form as the dominant group.
The rabbuck has been so successful that it is found in a wide variety of forms throughout the world - from the tundra and coniferous forests of the far north to the deserts and rain forests of the tropics.




THE PREDATORS

The rise of the predator rats - the earth's principal carnivore group

The rapide, Amphimorphodus longipes, a native of the northern plains, is built for speed. Its highly flexible spine gives it the added impetus to reach speeds of over 100 kilometers per hour.

 

The ravene, Vulpemys ferox, is about the size of the extinct fox or wild cat and preys on small mammals and birds. It has long claws and pointed stabbing fangs.

The janiset, Viverinus brevipes, is a long-bodied, burrowing predator, strongly resmbling the extinct stoats and weasels, and like them will swim, climb trees and tunnel underground in pursuit of its prey.

 

 

 

The falanx is the commonest species of predator rats found in temperate latitudes.

In the mammal world the predators were traditionally carnivores (members of the order carnivora) - specialized meat-eating animals with teeth modified for stabbing, killing and tearing flesh. Their legs were designed for leaping and producing a turn of speed that could quickly bring their chosen prey within killing distance. Wolves, lions, sabre-tooths, stoats - these were the creatures that fed on the docile herbivores and kept their numbers in check both during and before the Age of Man. However, being very specialized, these species tended not to have a great life span. They were so sensitive to changes in the nature and the populations of their prey that the average life of a carnivore genus was only six and a half million years. They reached their acme just before the Age of Man, but have since decreased in importance and are now almost extinct except for a number of aberrant and specialized forms found in the coniferous forest of the far north and in the South American Island Continent.
The place of the carnivores, as the principal mammal predators, is now occupied by a variety of mammal groups in different parts of the world. In temperate regions the descendants of the rodents occupy this niche.
When the carnivores were at their peak, the rodents, particularly the rats, began to acquire a taste for meat and animal waste. The spread of man to all parts of the world encouraged their proliferation and after man's demise they continued to flourish in the refuse created by the disruption and decay of human civilization. It is this adaptability that has ensured their survival.
Despite the specialized nature of their teeth, rats were able to live on a wide range of foods. At the front of their mouths they had two sharp gnawing incisors, which continued to grow throughout life to compensate for wear and which were separated by a gap from the back teeth. These were equipped with flat surfaces for grinding vegetable matter. This is very different from the typical carnivore dentition, which had cutting incisors at the front followed by a pair of stabbing canines and a row of shearing teeth at the back.
As the rats expanded to occupy the niches left by the dwindling carnivores their teeth evolved to fulfil their new role. The gnawing incisors developed long, stabbing points and were equipped with blades that could cut into and grip their prey. The gap between the incisors and the back teeth became smaller and the grinding molars became shearing teeth that worked with a scissor action. To make the dentition effective the jaw articulation changed from a rotary grinding motion into a more powerful up-and-down action. This dentition was crucial in the development of the predator rats and allowed them to radiate into the numerous forms and varieties seen throughout the world today.
In temperate latitudes the larger herbivores, the grazers and browsers of the plains and forests that were one time prey to the wolf, have now become the prey of the falanx, Amphimorphodus cynomorphus, a very large dog-like rat which hunts in packs. The evolution of this form involved the modification of the limbs from the fairly generalized scampering legs of the rat to very sophisticated running organs with small, thickly padded feet, and long shanks powered by strong muscles and tendons.




CREATURES OF THE UNDERGROWTH

Life beneath the trees of the broad-leaved forests

The tusked mole's strong limbs and powerful tusks enable it to burrow through the hardest and stoniest soils.

 

 

 

The tusked mole lies in wait just the soil surface listening for sounds of movement above. When it hears its prey approaching, it springs out, using its tail as a lever, grasping the creature with its teeth.

 

The oakleaf toad lures its prey with its long, worm-like tongue.

The undergrowth of a temperate wood, thick with humus and leaf-litter and added to annually by the autumnal shedding of deciduous leaves, provides a rich source of nourishment and shelter for all sorts of animals. The primary consumers of this material are bacteria and invertebrates, such as worms and slugs, which in turn provide food for many mammals and birds. The insectivores are therefore well represented in this habitat, not only in their primitive role of small-insect eater but also in a number of varieties that have adopted a predatory, carnivorous mode of life.
Among those that have kept to their original life style is the testadon, Armatechinos impenetrabilis, a descendant of the primitive hedgehog. The spines of its ancestor have been replaced by a series of hinged, armoured plates which can be drawn together into an impregnable sphere when the animal is threatened. When rolled up tightly it is almost impossible to grip or penetrate and even the most determined predator rat finds a meal from this little animal more trouble than it is worth.
The tusked mole, Scalprodens talpiforme, comes somewhere between the old order of insectivorous animals and the newer carnivorous ones. Looking very much like a mole of 50 million years ago, it leads a burrowing existence and has adopted the streamlined shape, velvety fur and spade-like feet of its distant cousin. However, here any resemblance stops. It has two huge tusks extending from its jaws, and a paddle-shaped tail. As it burrows, the animal pushes forward with its feet in a rolling motion so that its tusks ream out the soil in front of it. The loose soil is pushed back by the feet and compacted to the tunnel walls by its tail. As well as eating worms and burrowing invertebrates, it also preys on small surface-living animals, especially mice, voles and lizards.
The most interesting example of a previously insectivorous creature turned meat eater is the oakleaf toad, Grima frondiforme. It gets its name from a peculiar fleshy outgrowth on its back that looks exactly like a fallen oak leaf. The toad lies partly buried in the leaf litter, totally camouflaged and quite motionless except for its round, pink tongue which protrudes and wriggles about just like an earthworm. Any small animal that approaches to investigate falls victim to the toad's powerful jaws. The animal's only real enemy is the predator rat.
These two creatures, the oakleaf toad and the predator rat, have a curious relationship. Within their blood streams lives a fluke that spends the juvenile stage in the toad and the adult stage in the predator rat. When the fluke approaches adulthood it produces a dye that turns the leaf-like outgrowth on the toad's back bright emerald green. As this happens in winter the toad becomes highly conspicuous and is quickly eaten. In this way the fluke is transferred into the body of the predator rat, where it becomes sexually mature and breeds. The fluke's eggs return to the toad through the predator rat's faeces, which are eaten by beetles that are preyed on by the toad. As the fluke needs to spend a period of at least three years growing in the toad's body before it is ready to parasitize the predator rat, and as the toad is sexually mature at eighteen months, all toads have the opportunity of reproducing before being exposed to predation.




THE TREE DWELLERS

Mammals and birds of the tree-tops

The tree drummer's feet are covered with sensitive bristles that can detect the slightest movement in the bark beneath.

 

The tree goose or hanging bird in roosting position.

After making a hole in tree bark with its chisel teeth, the tree drummer removes the grub with its gristle-tipped proboscis.

 

 

Plant-eating mammals abound in the trees of the deciduous forests, eating shoots and leaf buds in the spring and fruits and nuts in the autumn. The long-bodied squirrel, known as the chirit, Tendesciurus rufus, is a typical plant-eating mammal. Its peculiar shape is a legacy from an immediate ancestor - the tree-burrowing rodent of the northern coniferous forests. As it spread south into the temperate woodlands it found that it no longer needed to make deep tunnels in the trees to escape the harsh winter, and as a result the animal's specialized chiselling and gnawing teeth became smaller, its dentition reverting to be more like that of its distant ancestor the grey squirrel. Its bodily shape, however, was still perfectly adapted to life in the trees and remained unchanged.
Now that the animal no longer led a burrowing existence, its legs and feet had to evolve to suit its new environment. Its hind feet, although small and short, became very powerful and developed strong, gripping claws. The underside of its short tail grew hard and scaly and with its hind feet formed a strong three-point anchor that could secure the animal to the tree while it reached out to collect food.
As its squirrel ancestor's jumping ability has completely disappeared, the animal can only move from one tree to another by reaching out and grasping an extended branch. For this reason the chirit is found most often in dense thickets, where the trees are close together. Its only enemies are birds of prey, and it is really only vulnerable to these when feeding in the topmost branches. It retains the predilection of the burrowing squirrel for making nests in holes in trees and often occupies holes and hollows excavated by wood-boring birds.
Wood boring is the speciality of a group of insectivores known as tree drummers, Proboscisuncus spp. These animals, basically shrew-like in form, subsist on a diet of grubs and insects, which they gouge out from crevices in the bark. They have masses of sensory bristles on their feet and very large ears, which help them to detect the movement of grubs burrowing in the wood. When a tree drummer finds a grub it drives its chisel-like teeth into the bark to make a hole big enough to enable it to remove the grub with its trunk-like proboscis. Sometimes the grub becomes skewered on its chisel teeth and needs to be carefully plucked off before being eaten.
It is really the birds that are the masters of the trees. After the great reptiles became extinct, over a hundred million years ago, the birds expanded into an enormous number of species. Being primarily designed for flying, birds had access to the tree-tops in a way that few other animals had, and finding that they were safer there than on the ground they soon became perfectly adapted to this new habitat. As a result many woodland birds have developed feet with curved opposable toes that are ideal for gripping branches. In one species, the tree goose or hanging bird, Pendavis bidactylus, these toes have been reduced to two. They are permanently curved and enable the bird to hang upside down without effort. Because of the bird's size and weight, this attitude is much easier to maintain over long periods than an upright stance, and it has taken to spending long periods roosting in this position.




NOCTURNAL ANIMALS

The night-life of the temperate forest

The purrip bat's sensitive ears are positioned far forward at the front of its face to provide it with the largest possible sound-collecting surface.

 

 

The lutie's large rabbit-like ears betray its ancestry.

The shrock's outward similarity to the badger is an excellent example of convergent evolution.

The largest of the owl-eyed predatory birds stands more than a metre high.

As night falls in the temperate woodland, the sleeping animals of the day are replaced by a completely new set of creatures. Nocturnal birds, bats and insects - a whole array of creatures is found that are as diverse and numerous as those of the daytime. As dusk falls and the moths and night-active flies take to the air the insectivorous bats appear to feed on them. Bats have proved so successful in their shape and life style that in most parts of the world they have remained remarkably stable in shape and form ever since they first appeared over a hundred million years ago. Save for the development of a more sophisticated echolocation system, positioned at the front of the face, and the absence of eyes, little else has changed,
The purrip bat, Caecopterus sp., so called because of its curious voice, is found throughout temperate latitudes. Unlike the earlier bats which generally navigated using high-pitched sounds, the purrip bat uses a much wider range of frequencies extending well into the audible level, giving it a much more sophisticated picture of the terrain.
Great birds of prey, which combine the characteristics of the former eagles and owls, wing their way silently through the branches, ever watching for an unwary movement on the ground that would denote the presence of a small animal. Their large forward-facing eyes, acting like wide-aperture lenses to increase the amount of light reaching the retina, give a three-dimensional image over their entire field of vision and enable them to accurately gauge distances and hunt in almost pitch darkness. Their prey includes the lutie, Microlagus mussops, a descendant of the rabbit.
The luties live in direct competition with the ancient groups of small rodents - the mice and voles. In some areas the luties have replaced the rodents completely, whereas in other parts of the woodlands, where the conditions particularly favour them, the rodents have remained successful. The luties resemble the small rodents in many respects, particularly in size, but their rabbit ancestry is obviously displayed in the shape of the head and tail. They feed mostly at night, nesting during the day in crevices among tree roots or in holes in the ground.
Another small animal that provides food for birds of prey is the truteal, Terebradens tubauris, an insectivore related to the chisel-toothed shrews of the trees. The incisors of both the upper and lower jaws of this animal are extended forward to form a structure like a bird's beak, which acts as a probe to catch worms and burrowing insects in soft earth and leaf litter. The truteal is completely blind and retains no vestiges of eyes. It is, however, equipped with a large number of sensory whiskers and extremely acute hearing. Its ears, which are enormous for the size of its body, can be rolled into trumpets by a unique set of muscles located at their base and then pressed to the ground to listen for sounds of burrowing.
The shrock, Melesuncus sylvatius, is a much larger animal. Descended from insectivore stock, it has a size and shape comparable to that of the extinct badger. It makes nightly forays through the undergrowth and will take any prey that it chances upon. It has a long snout and broad forepaws with which it digs after burrowing animals and excavates its own family nest in soft soil under tree roots.




THE WETLANDS

Life in the fens and marshes

The pfrit's mouth extends forward into a long tubular snout, which carries a set of fine teeth at the tip capable of piercing the outer skin of an insect larva.

Once the angler heron has baited its "fish pond" it remains close by, watching motionless from the reeds.

The long-necked dipper

Flying wing of juvenile

The wing of the breeding adult is degenerate and used only for balance and in swimming under water.

 

 

 

 

In temperate latitudes wetland areas are comparatively isolated pockets of land found scattered widely across the Northern Continent, As well as strictly water habitats such as ponds, lakes and rivers, they also include stretches of saltmarsh and fenland found near the sea, mires and peat bogs found in poorly drained inland regions and areas of regular inundation.
The conditions found throughout this range of habitats is so diverse in terms of salinity, oxygenation, light penetration and water currents that very nearly every individual location has its own little ecosystem and associated fauna, and almost every animal group is represented.
One of the most unusual water-living mammals is the pfrit, Aquambulus hirsutus, a tiny insectivore descended from the primitive shrews. Its length, excluding its tail, is less than five centimetres, which puts it among the smallest mammals in existence. Although its body is thin, its feet and tail are broad and are covered with water-repellent hairs, which spread its weight over such a large area that it can skate across the water without breaking the surface tension. It lives mainly on the larvae of mosquitoes and midges that are found just under the water surface. It feeds on them by piercing their outer cuticles with its long, hairless snout and draining them of their vital juices while they are still in the water. In this way the pfrit avoids disturbing the water surface, which would both upset the surface tension and frighten away its prey.
A mammal frequently found near river banks and lake sides is the reedstilt, Harundopes virgatus. Its long, slender legs and neck and vertical stripes render it almost totally invisible among reeds, where it is frequently found fishing. Its head and neck are most unusual. Practically all mammals have seven neck vertebrae, but the reedstilt has fifteen. In evolutionary terms the extra vertebrae have appeared quite recently and result from the fact that, in fishing, longer-necked individuals have an advantage over the others. The tooth pattern is degenerate - the incisors, canines and molars having all reverted to an almost reptilian condition in which they are all of the same shape. The reedstilt uses this combination of neck and tooth features to catch fish by darting out its long neck and snapping shut its needle-pointed teeth.
Fishing skills have also been developed to a high degree by the angler heron, Butorides piscatorius. This bird, an inhabitant of the North American subcontinent, creates shallow ponds at the water's edge in the shade of overhanging trees by scraping at the river bottom and constructing shallow dams. On the shore nearby it accumulates a heap of droppings and fish remains to attract beetles and flies. These it then picks up and drops into the shallow water to entice the fish into its pond, where they are easily caught.
Although there are many examples of flightless birds, the long-necked dipper, Apterocinclus longinuchus, a river bird of the European sub-continent, is the only bird that spends part of its life with the capacity for flight and the rest flightless. During its early life the bird develops wings in the normal way, but once it has migrated away from its natal nesting site it becomes totally earth-bound and pursues a purely terrestrial - aquatic existence. Its wings now no longer necessary, lose their power and gradually atrophy.




CONTENTS

INTRODUCTION BY DESMOND MORRIS 9

AUTHOR'S INTRODUCTION 10

EVOLUTION 11

Cell Genetics : Natural Selection : Animal Behaviour : Form and Development :
Food Chains

HISTORY OF LIFE 22

The Origins of Life : Early Living Forms : The Age of Reptiles :
The Age of Mammals : The Age of Man

LIFE AFTER MAN 33

The World after Man

TEMPERATE WOODLANDS AND GRASSLANDS 36

The Rabbucks : The Predators : Creatures of the Undergrowth :
The Tree Dwellers : Nocturnal Animals : The Wetlands

CONIFEROUS FORESTS 50

The Browsing Mammals : The Hunters and the Hunted : Tree Life

TUNDRA AND THE POLAR REGIONS 58

The Migrants : The Meaching and its Enemies : The Polar Ocean :
The Southern Ocean : The Mountains

DESERTS : THE ARID LANDS 70

The Sand Dwellers : Large Desert Animals : The North American Deserts

TROPICAL GRASSLANDS 78

The Grass-eaters : Giants of the Plains : The Meat-eaters

TROPICAL FORESTS 86

The Tree-top Canopy ; Living in the Trees : The Forest Floor :
Living with Water : Australian Forests : The Australian Forest Undergrowth

ISLANDS AND ISLAND CONTINENTS 100

South American Forests : South American Grasslands : The Island of Lemuria :
The Islands of Batavia : The Islands of Pacaus

FUTURE 113

The Destiny of Life

APPENDIX 117

Glossary : The Tree of Life : Index : Acknowledgements

 

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