Zebra And Antelope And Koala

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Zebras are several species of African equids (horse family) united by their distinctive black and white stripes. Their stripes come in different patterns unique to each individual. They are generally social animals that live in small harems to large herds. Unlike their closest relatives, horses and asses, zebras have never been truly domesticatedSony VAIO PCG-31114V battery.

There are three species of zebras: the plains zebra, the Grévy's zebra and the mountain zebra. The plains zebra and the mountain zebra belong to the subgenus Hippotigris, but Grevy's zebra is the sole species of subgenus Dolichohippus. The latter resembles an ass, to which it is closely related, while the former two are more horse-like. All three belong to the genus Equus, along with other living equidsSony VAIO PCG-31113V battery.

The unique stripes of zebras make these among the animals most familiar to people. They occur in a variety of habitats, such as grasslands, savannas, woodlands, thorny scrublands, mountains, and coastal hills. However, various anthropogenic factors have had a severe impact on zebra populations, in particular hunting for skins and habitat destructionSony VAIO PCG-31112V battery. Grevy's zebra and the mountain zebra are endangered. While plains zebras are much more plentiful, one subspecies, the quagga, went extinct in the late 19th century, though there is currently a project, called the Quagga Project, that aims to breed zebras that are phenotypically similar to the quagga in a process called breeding backSony VAIO PCG-31111V battery.

Etymology

Zebra in English dates back to c.1600, from Italian Zebra, perhaps from Portuguese, which in turn is said to be Congolese (as stated in the Oxford English Dictionary). The Encarta Dictionary says its ultimate origin is uncertain, but perhaps it may come from Latin Equiferus meaning "Wild horse," from equus "horse" and ferus "wild, untamed"Sony VAIO PCG-31114M battery.

Taxonomy and evolution

See also: Horse evolution

Zebras evolved among the Old World horses within the last 4 million years. Grevy's zebras (and perhaps also Mountain Zebras) are with asses and donkeys in a separate lineage from the other zebra lineages.[2] This means either that striped equids evolved more than once, or that common ancestors of zebras and asses were striped and only zebras retained the stripesSony VAIO PCG-31113M battery. Extensive stripes are posited to have been of little use to equids that live in low densities in deserts (like asses and some horses) or ones that live in colder climates with shaggy coats and annual shading (like some horses).

Fossils of an ancient equid were discovered in the Hagerman Fossil Beds National Monument in Hagerman, Idaho. It was named the Hagerman horse with a scientific name of Equus simplicidens. It is believed to have been similar to the Grevy's zebra. Sony VAIO PCG-31112M battery The animals had stocky zebra-like bodies and short, narrow, donkey-like skulls.[5] Grevy's zebra also has a donkey-like skull. The Hagerman horse is also called the American zebra or Hagerman zebra.

Classification

Zebras in Botswana

There are three extant species. Collectively, two of the species have eight subspecies (seven extant). Zebra populations are diverse, and the relationships between and the taxonomic status of several of the subspecies are not well knownSony VAIO PCG-31111M battery.

The plains zebra (Equus quagga, formerly Equus burchelli) is the most common, and has or had about twelve subspecies distributed across much of southern and eastern Africa. It, or particular subspecies of it, have also been known as the common zebra, the dauw, Burchell's zebra (actually the subspecies Equus quagga burchellii), Chapman's zebra, Wahlberg's zebra, Selous' zebraSony VAIO PCG-41111V battery, Grant's zebra, Boehm's zebra and the quagga (another extinct subspecies, Equus quagga quagga).

The mountain zebra (Equus zebra) of southwest Africa tends to have a sleek coat with a white belly and narrower stripes than the plains Zebra. It has two subspecies and is classified as vulnerableSony VAIO PCG-41112M battery.

Grévy's zebra (Equus grevyi) is the largest type, with a long, narrow head, making it appear rather mule-like. It is an inhabitant of the semiarid grasslands of Ethiopia and northern Kenya. Grévy's zebra is the rarest species, and is classified as endangered.

Although zebra species may have overlapping ranges, they do not interbreed. This held true even when the quagga and Burchell's race of plains zebra shared the same areaSony VAIO PCG-41111M battery. In captivity, plains zebras have been crossed with mountain zebras. The hybrid foals lacked a dewlap and resembled the plains zebra apart from their larger ears and their hindquarters pattern. Attempts to breed a Grévy's zebra stallion to mountain zebra mares resulted in a high rate of miscarriage. In captivity, crosses between zebras and other (non-zebra) equines have produced several distinct hybrids, including the zebroid, zeedonk, zony, and zorseSONY VAIO PCG-21214V battery. In certain regions of Kenya, plains zebras and Grévy's Zebra coexist, and fertile hybrids occur.[6]

Physical attributes

Size and weight

The common plains zebra is about 50–52 inches (12.2-13 hands, 1.3 m) at the shoulder with a body ranging from 6–8.5 feet (2–2.6 m) long with an 18-inch (0.5 m) tail. It can weigh up to 770 pounds (350 kg), males being slightly bigger than females. Grévy's Zebra is considerably larger, while the mountain zebra is somewhat smaller. SONY VAIO PCG-21213V battery

Stripes

It was previously believed that zebras were white animals with black stripes, since some zebras have white underbellies. Embryological evidence, however, shows that the animal's background color is black and the white stripes and bellies are additions.[3] It is likely that the stripes are caused by a combination of factors. SONY VAIO PCG-21212V battery

A mother nursing her young blends into a stand of deadwood.

The stripes are typically vertical on the head, neck, forequarters, and main body, with horizontal stripes at the rear and on the legs of the animal. The "zebra crossing" is named after the zebra's black and white stripes.

A wide variety of hypotheses have been proposed to account for the evolution of the striking stripes of zebras. The more traditional of these (1 & 2, below) relate to camouflageSONY VAIO PCG-21212M battery.

1. The vertical striping may help the zebra hide in grass. While seeming absurd at first glance, considering that grass is neither white nor black, it is supposed to be effective against the zebra's main predator, the lion, which is color blind[dubious – discuss]. In addition, even at moderate distances, the striking striping merges to an apparent greySONY VAIO PCG-21211M battery.

2. Another hypothesis is that since zebras are herd animals, the stripes may help to confuse predators—a number of zebras standing or moving close together may appear as one large animal, making it more difficult for the lion to pick out any single zebra to attack.

3. It has been suggested that the stripes serve as visual cues and identification. SONY VAIO PCG-51212M batteryAlthough each striping pattern is unique to each individual, it is not known whether zebras can recognize one another by their stripes.

4. At least two experiments indicate that the disruptive colouration is an effective means of confusing the visual system of flies, in one case the blood-sucking tsetse fly, in another horseflies (tabanids) SONY VAIO PCG-51211M battery.

5. Alternative theories include that the stripes coincide with fat patterning beneath the skin, serving as a thermo-regulatory mechanism for the zebra, or that wounds sustained disrupt the striping pattern to clearly indicate the fitness of the animal to potential mates.[citation needed]

A zebra walkingSONY VAIO PCG-51112M battery

Gaits

Like horses, zebras walk, trot, canter and gallop. They are generally slower than horses, but their great stamina helps them outpace predators. When chased, a zebra will zig-zag from side to side, making it more difficult for the predator. When cornered, the zebra will rear up and kick or bite its attackerSONY VAIO PCG-51111M battery.

Face of a zebra

Senses

Zebras have excellent eyesight. It is believed that they can see in color. Like most ungulates, the zebra has its eyes on the sides of its head, giving it a wide field of view. Zebras also have night vision, although not as advanced as that of most of their predators.

Zebras have excellent hearing, and tend to have larger, rounder ears than horses. Like horses and other ungulates, zebra can turn their ears in almost any direction. In addition to eyesight and hearing, zebras have an acute sense of smell and tasteSONY VAIO PCG-51111V battery.

Ecology and behavior

Harems

Zebras in Tanzania

Like most members of the horse family, zebras are highly social. Their social structure, however, depends on the species. Mountain zebras and plains zebras live in groups, known as 'harems', consisting of one stallion with up to six mares and their foals. Bachelor males either live alone or with groups of other bachelors until they are old enough to challenge a breeding stallionSONY VAIO PCG-81211V battery. When attacked by packs of hyenas or wild dogs a zebra group will huddle together with the foals in the middle while the stallion tries to ward them off.

Unlike the other zebra species, Grevy's zebras do not have permanent social bonds. A group of these zebras rarely stays together for more than a few months. The foals stay with their mothers, while adult males live alone. Like the other two zebra species, bachelor male zebras will organize in groupsSONY VAIO PCG-81111V battery.

Like horses, zebras sleep standing up, and only sleep when neighbors are around to warn them of predators.

Communication

A zebra feeding on grass

Zebras communicate with each other with high pitched barks and whinnying. Grevy's zebras make mule-like brays. A zebra's ears signify its mood. When a zebra is in a calm, tense or friendly mood, its ears stand erect. When it is frightened, its ears are pushed forwardSONY VAIO PCG-81212M battery. When angry, the ears are pulled backward. When surveying an area for predators, zebras will stand in an alert posture; with ears erect, head held high, and staring. When tense they will also snort. When a predator is spotted or sensed, a zebra will bark (or bray) loudly.

Hartmann's Mountain Zebra with a Barbary sheep behind it, in captivity at Ueno Zoo, in Japan. (video) Sony VAIO PCG-81112M battery

Food and foraging

Zebras feed almost entirely on grasses, but may occasionally eat shrubs, herbs, twigs, leaves and bark. Their digestive systems allow them to subsist on diets of lower nutritional quality than that necessary for other herbivores.

Reproduction

Female zebras mature earlier than the males, and a mare may have her first foal by the age of three. Males are not able to breed until the age of five or sixSONY VAIO PCG-71111M battery. Mares may give birth to one foal every twelve months. She nurses the foal for up to a year. Like horses, zebras are able to stand, walk and suckle shortly after they are born. A zebra foal is brown and white instead of black and white at birth.

Plains and mountain zebra foals are protected by their mothers, as well as the head stallion and the other mares in their group. Grevy's zebra foals have only their mother as a regular protector, since, as noted above, Grevy's zebra groups often disband after a few monthsSONY VAIO PCG-7192V battery.

Human interactions

Lord Rothschild with his famed zebra carriage (sp. Equus quagga burchellii), which he frequently drove through London

Domestication

Attempts have been made to train zebras for riding, since they have better resistance than horses to African diseases. Most of these attempts failed, though, due to the zebra's more unpredictable nature and tendency to panic under stress. For this reason, zebra-mules or zebroidsSONY VAIO PCG-7191V battery (crosses between any species of zebra and a horse, pony, donkey or ass) are preferred over purebred zebras.

In England, the zoological collector Lord Rothschild frequently used zebras to draw a carriage. In 1907, Rosendo Ribeiro, the first doctor in Nairobi, Kenya, used a riding zebra for house calls. In the mid-19th century, Governor George Grey imported zebras to New Zealand from his previous posting in South Africa, and used them to pull his carriage on his privately owned Kawau IslandSONY VAIO PCG-7196M battery.

A tamed zebra being ridden in East Africa

Captain Horace Hayes, in "Points of the Horse" (circa 1893), compared the usefulness of different zebra species. In 1891, Hayes broke a mature, intact mountain zebra stallion to ride in two days time, and the animal was quiet enough for his wife to ride and be photographed upon. He found the Burchell's zebra easy to break, and considered it ideal for domesticationSONY VAIO PCG-7195M battery, as it was immune to the bite of the tsetse fly. He considered the quagga (now extinct) well-suited to domestication due to being easy to train to saddle and harness.[12]

Conservation

Modern man has had great impact on the zebra population. Zebras were, and still are, hunted for their skins, and for meat. They also compete with livestock for forage,[13] and are sometimes culledSONY VAIO PCG-7194M battery.

The Cape mountain zebra was hunted to near extinction, with less than 100 individuals by the 1930s. The population has increased to about 700 due to conservation efforts, though. Both mountain zebra subspecies are currently protected in national parks, but are still endangered.

Zebras on the Botswana coat of armsSONY VAIO PCG-7192M battery.

The Grevy's zebra is also endangered. Hunting and competition from livestock have greatly decreased their population. Because of the population's small size, environmental hazards, such as drought, are capable of affecting the entire species. Plains zebras are much more numerous and have a healthy population. Nevertheless, they too have been reduced by hunting and loss of habitat to farming. One subspecies, the quagga, is now extinctSONY PCG-8113M battery.

Cultural depictions

Zebras have been the subject of African folk tales which tell how they got their stripes. According to a Bushmen folk tale of Namibia, the zebra was once all white, but acquired its black stripes after a fight with a baboon over a waterhole. After kicking the baboon so hard, the zebra lost his balance and tripped over a fire, and the fire sticks left scorch marks all over his white coat. SONY PCG-8112M battery In the film Fantasia, two centaurs are depicted being half human and half zebra, instead of the typical half human and half horse.[15]

Illustration of a zebra by Ludolphus

Zebra are a popular subject in art.[16] The fourth Mughal emperor Jahangir (r.1605-24), commissioned a painting of the zebra, which was completed by Ustad Mansur.[17] Zebra stripes are also a popular style for furniture, carpets and fashionSONY PCG-7134M battery .

When depicted in movies and cartoons, zebras are most often miscellaneous characters, but have had some starring roles, notably in Madagascar and Racing Stripes. Zebras also serve as mascots and symbols for products and corporations, notably Zebra Technologies and Fruit Stripe gum. Zebras are featured on the coat of arms of BotswanaSONY PCG-7131M battery .

Antelope is a term referring to many even-toed ungulate species indigenous to various regions in Africa and Eurasia. Antelopes comprise a miscellaneous group within the family Bovidae, encompassing those old-world species that are neither cattle, sheep, buffalo, bison, nor goats. A group of antelope is called a herdSONY PCG-7122M battery.

Distinctions from even-toed ungulates

No antelope species are native to Australasia, or Antarctica. Nor do any extant species occur in the Americas, though at least one saiga species occurred in parts of North America during the Pleistocene. The Pronghorn of North America, though sometimes known colloquially as Pronghorn Antelope, is not a member of the family BovidaeSONY PCG-7121M battery, but the family Antilocapridae and accordingly is not a true antelope. Among their most obvious differences, pronghorns have branching horns, of which they shed the outer horny sheaths annually, in which they in turn differ from deer. The horns of pronghorns and the antlers of deer contrast in two ways with the horns of true antelopesSONY PCG-7113M battery; firstly, although true antelopes have horns of various shapes according to species, whether straight, curved, helical, or otherwise, and although their horns have cores of living bone, their horns always are unbranched. Secondly, the antelope horn never is shed, either wholly as in the antlers of deer, nor in part, as in the pronghornSONY PCG-7112M battery .

Apart from not shedding their horns, antelope, and bovids in general, differ from deer in several other ways. Probably the most obvious is that their horns are perennial living bone covered with strong, thick layers of dead horn tissue, whereas antlers, in those deer that have them, are covered with living skin ("velvet") only while growing. The velvet then is shed and the bony tissue, after it has matured, dies and is shed at the end of the seasonSONY PCG-8Z3M battery .

Etymology

Illustration from The History of Four-footed Beasts (1607)

The English word "antelope" first appears in 1417 and is derived from the Old French antelop, itself derived from Medieval Latin ant(h)alopus, which in turn comes from the Byzantine Greek word anthólops, first attested in Eustathius of Antioch (c.336), according to whom it was a fabulous animal "haunting the banks of the Euphrates, very savageSONY PCG-8Z2M battery, hard to catch and having long saw-like horns capable of cutting down trees".[2] It perhaps derives from Greek anthos (flower) and ops (eye), perhaps meaning "beautiful eye" or alluding to the animals long eyelashes; however this may be a later folk etymology. The word talopus and calopus, from Latin, came to be used in heraldry. In 1607 it was first used for living, cervine animalsSONY PCG-8Z1M battery.

Species

There are 91 species, most of which are native to Africa, in about 30 genera. The classification of tribes or subfamilies within Bovidae is still a matter of debate, with several alternative systems proposed.

Antelope are not a cladistic or taxonomically defined group. The term is used loosely to describe all members of the family Bovidae which do not fall under the category of sheepSONY PCG-8Y3M battery, cattle, or goat. Usually all species of the Alcelaphinae, Antilopinae, Hippotraginae, Reduncinae, Cephalophinae, many Bovinae, the Grey Rhebok, and the impala are called antelopes.

Distribution and habitat

Most species of antelope are native to Africa, but some occur in Asia. The Arabian Peninsula is home to the Arabian Oryx and Dorcas Gazelle. India is home to the Nilgai, Chinkara, Blackbuck, Tibetan antelope and Four-horned Antelope, while Russia and Central Asia have the Tibetan antelope, and Saiga AntelopeSONY PCG-8Y2M battery.

Many species of antelope have been imported to other parts of the world, especially the United States, for exotic game hunting. Due to the spectacular leaping and evasive skills of some species, individuals may escape. Texas in particular has high numbers of gaming ranches, as well as habitat and climate that are very hospitable to African and Asian plains antelope speciesSONY PCG-7Z1M battery. As such, wild populations of Blackbuck Antelope, Gemsbok, and Nilgai exist in Texas, though they are not native to the area.[3]

Antelope exist in a wide range of habitats. Numerically, most exist in the African savannahs. However, there are many species of more secluded forest antelope, as well as the extreme-cold living Saiga, desert adapted Arabian Oryx, the rocky kopje-living klipspringer, and semi-aquatic sitatunga. SONY PCG-6W2M battery

Species of forest, woodland, or bush tend to be sedentary, but many of the plains species undertake huge migrations. These migrations enable grass-eating species to follow the rains and therefore their food supply. The gnus and gazelles of East Africa perform some of the most impressive mass migratory circuits of all mammals. SONY PCG-5J5M battery

Morphology

Gerenuks can stand erect on their hind legs to browse on high foliage

All bovids have even-toed hooves, horizontal pupils, ruminating guts, and (in at least the males) bony horns. These basic characteristics, however, mask huge differences in appearance between antelopes, cattle, goats, and sheep, and among the antelopes themselves.[6] For example, a male Common Eland can measure 178 centimetres (70 in) at the shoulder and weigh almost 950 kilograms (2,100 lb) SONY PCG-5K2M battery, whereas an adult Royal Antelope may stand only 24 centimetres (9.4 in) at the shoulder and weigh a mere 1.5 kilograms (3.3 lb).

Not surprisingly for animals with long, slender yet powerful legs, many antelopes have long strides and can run fast. Some (e.g. Klipspringer) are also adapted to climbing in rock kopjes. Both Dibatags and Gerenuks habitually stand on their two hind legs to reach acacia and other tree foliageSONY PCG-5K1M battery . Different antelope have different body types which can affect movement. Duikers are short, bush-dwelling antelope that can pick through dense foliage and dive into the shadows rapidly. Gazelles and Springbok are known for their speed and leaping abilities. Even larger antelope, such as Nilgai, Elands, and Kudus, are capable of jumping 8 feet (2.4 m) or greater, although their running speed is restricted by their greater massSONY PCG-5J4M battery .

Antelopes have a wide variety of coverings, through most have a dense coat of short fur. In most species, the coat (pelage) is some variation of a brown colour (or several shades of brown); often with white or pale under-bodies. Exceptions include the zebra-marked Zebra Duiker; the grey, black, and white Jentink's DuikerSONY PCG-5J1M battery ; and the Black Lechwe. Most of the "spiral-horned" antelopes have pale vertical stripes on their backs. Many desert and sub-desert species are particularly pale, some almost silvery or whitish (e.g. Arabian Oryx); the Beisa and Southern Oryxes have gray and black pelage with vivid black-and-white faces. Common features of various gazelles are a white rumpSONY PCG-5G2M battery, which flashes a warning to others when they run from danger, and a dark stripe mid-body (the latter feature is also shared by the Springbok and Beira). The Springbok also has a pouch of white brushlike hairs running along its back, which opens up when the animal senses danger, causing the dorsal hairs to stand on endSony VAIO PCG-8131M battery.

Antelopes are ruminants, and thus have well-developed molar teeth, which grind cud (food balls stored in the stomach) into a pulp for further digestion. They have no upper incisors, but rather a hard upper gum pad, against which their lower incisors bite to tear grass stems and leaves.

Like many other herbivores, antelopes rely on keen senses to avoid predatorsSony VAIO PCG-8152M battery. Their eyes are placed on the sides of their heads, giving them a broad radius of vision with minimal binocular vision. The fact that most species have their pupils elongated horizontally also helps in this respect. Acute senses of smell and hearing, give antelope the ability to perceive danger at night out in the open (when predators are often on the prowl). These same senses play an important role in contact between individuals of the same speciesSony VAIO PCG-31311M battery: markings on head, ears, legs, and rumps are used in such communication—many species "flash" such markings, as well as their tails; vocal communications include loud barks, whistles, "moos" and trumpeting; many species also use scent marking to define their territories or simply to maintain contact with their relatives and neighborsSony VAIO PCG-31111M battery.

Many antelope are sexually dimorphic. In most species, both sexes have horns, but those of males tend to be larger. There is a tendency for males to be larger than the females; however, exceptions in which the females tend to be heavier than the males include the Bush Duiker, Dwarf Antelope, Cape Grysbok, and Oribi, all rather small speciesSony VAIO PCG-8112M battery. A number of species have hornless females (e.g. Sitatunga, Red Lechwe, and Suni). In some species, the males and females have different coloured pelage (e.g. Blackbuck and Nyala).

Antelope horns

The size and shape of antelope horns varies immensely. Those of the duikers and dwarf antelopes tend to be simple "spikes", but differ in the angle to the head from backward curved and backward pointing (e.g. Yellow-backed Duiker)Sony VAIO PCG-7186M battery to straight and upright (e.g. Steenbok). Other groups have twisted (e.g. Common Eland), spiral (e.g. Greater Kudu), "recurved" (e.g. the reedbucks), lyrate (e.g. impala), or long, curved (e.g. the oryxes) horns. Horns are not shed and their bony core is covered with a thick, persistent sheath of horny material, both of which features distinguish them from antlers. Sony VAIO PCG-7171M battery

Horns are efficient weapons and tend to be better developed in those species where males fight over females (large herd antelope) than in solitary or lekking species. With male-male competition for mates, horns are clashed in combat. It is much more common for males to use their horns against each other than against another speciesSony VAIO PCG-9Z1M battery. The boss of the horns is typically arranged in such a way that two antelope striking at each other's horns cannot crack each other's skulls, making a fight via horn more ritualized than dangerous. Many species have ridges in their horns for at least 2/3 the length of their horns, but these ridges are not a direct indicator of ageSony VAIO PCG-5S1M battery.

Behavior

Mating strategies

Forest-dwelling bushbuck.

Antelope are often classified by their reproductive behavior.

Small antelope, such as dik-diks, tend to be monogamous. They live in a forest environment with patchy resources, and a male is unable to monopolize more than one female due to this sparse distribution. Larger forest species often form very small herds of 2–4 females and 1 male.

Some species such as lechwe pursue a lek breeding systemSony VAIO PCG-5P1M battery. In this, the males gather on a lekking ground and compete for a small territory, while the females appraise males and choose one with which to mate.

Large grazing antelope, such as impala or wildebeest form large herds made up of many females and a single breeding male, which excludes all other males, often by combat.

Defense

Fast running gazelles prefer open grassland habitat

Antelope pursue a number of defense strategies, often dictated by their morphology.

Large antelope that gather in large herdsSony VAIO PCG-5N2M battery, such as wildebeest rely on numbers and running speed for protection. In some species, adults will circle around the offspring, protecting them from predators when threatened. Many forest antelope rely on cryptic coloring and good hearing to avoid predators. Forest antelope often have very large ears and a dark or striped coloration. Small antelope, especially duikers, evade predation by jumping into dense bush where the predator cannot pursue. Sony VAIO PCG-3C2M battery Springboks use a behavior known as stotting to confuse predators.

Open grassland species have nowhere to hide from predators so they tend to be fast runners. They are agile and have good endurance—these are advantages when pursued by sprint-dependent predators like cheetah, which are the fastest of land animals but tire quickly. Reaction distances vary with predator species and predator behaviourSony VAIO PCG-8161M battery. For example, gazelles may not flee from a lion until it is closer than 200 m (650 ft)—lions hunt as a pride or by surprise, usually by stalking, one that can be seen clearly is unlikely to attack. However, sprint-dependent cheetahs will cause gazelles to flee at a range of over 800 m (0.5 mile).

Status

About 25 species are rated by the IUCN as endangered,[10] such as the Dama Gazelle and Mountain NyalaSony VAIO PCG-8141M battery. A number of subspecies are also endangered, including the Giant Sable Antelope and mhorr gazelle. The main causes for concern for these species are habitat loss, competition with cattle for grazing, and trophy hunting.

The chiru or Tibetan antelope is hunted for its pelt, which is used in making shahtoosh, an incredibly fine material used in shawls. The fur can only be removed from dead animalsSony VAIO PCG-3J1M battery, and each animal yields very little of the downy fur, so multiple antelope must be killed to make a single shawl. This unsustainable demand has led to enormous declines in the chiru population.

The Saiga Antelope is hunted for its horns, which are considered an aphrodisiac by some cultures. Only the males carry the horns, and have been heavily hunted to the point where some herds contain up to 800 females and a single male. The species has shown a steep decline and is critically endangeredSony VAIO PCG-3H1M battery.

Lifespan

It is difficult to determine how long antelope live in the wild. With the preference of predators towards old and infirm individuals which can no longer sustain peak speeds, few wild prey-animals live as long as their biological potential. In captivity, wildebeest have lived beyond 20 years old, and impalas have reached their late teensSony VAIO PCG-3F1M battery. In the wild, few individuals of prey species live to old age, as the old and weak are easier prey for predators; antelopes are no exception to this rule.[11]

Humans

Culture

Greater Kudu horn shofar.

The antelope's horn is prized for medicinal and magical powers in many places. The horn of the male Saiga in Eastern practice is ground as an aphrodisiac, for which it has been hunted nearly to extinction.[12] In the Congo, it is thought to confine spirits. Christian iconography sometimes uses the antelope's two horns as a symbol of the two spiritual weapons that Christians possess
Sony VAIO PCG-3C1M battery
: the Old Testament and the New Testament. Their ability to run swiftly has also led to their association with the wind, such as in the Rig Veda, as the steeds of the Maruts and the wind god Vayu.

Domestication

Domestication of animals requires certain traits in the animal which antelope do not typically display. Most species are difficult to contain in any density, due to territoriality of males or in the case of oryxes (which have a relatively hierarchical social structure) Sony VAIO PCG-9Z2L battery, an aggressive disposition that can easily kill a human. Because many have extremely good jumping abilities, providing adequate fencing is a challenge. Also, antelope will consistently display a fear response to perceived predators, such as humans, making them very difficult to herd or handle. Although antelopes have a diet and rapid growth rate highly suitable for domesticationSony VAIO PCG-9Z1L battery, this tendency to panic and their non-hierarchical social structure explains why farm-raised antelope is uncommon. Ancient Egyptians kept herds of gazelles and Addax for meat, and occasionally pets. It is unknown whether they were truly domesticated, but it seems unlikely as no domesticated gazelles exist today.

However, humans have had success taming certain species, such as the elands. These antelope sometimes jump over each other's backs when alarmedSony VAIO PCG-9131L battery, but this incongruous talent seems to be exploited only by wild members of the species; tame elands do not take advantage of it and can be enclosed within a very low fence. Their meat, milk, and hides are all of excellent quality, and experimental eland husbandry has been going on for some years in both Ukraine and Zimbabwe. In both locations the animal has proved wholly amenable to domestication.[13] For further information, see animal domesticationSony VAIO PCG-8161L battery.

[edit]Hybrid antelope

A wide variety of antelope hybrids have been recorded in zoos, game parks, and wildlife ranches. This is due to either a lack of more appropriate mates in enclosures shared with other species or a misidentification of species. The ease of hybridization shows how closely related some antelope species are. With few exceptions, most hybrid antelope occur only in captivitySony VAIO PCG-8152L battery.

Most hybrids occur between species within the same genus. All reported examples occur within the same sub-family. As with most mammal hybrids, the less closely related the parents, the more likely that the offspring will be sterile.[11]

The koala (Phascolarctos cinereus) is an arboreal herbivorous marsupial native to Australia, and the only extant representative of the family PhascolarctidaeSony VAIO PCG-8141L battery.

The koala is found in coastal regions of eastern and southern Australia, from Adelaide to the southern part of Cape York Peninsula. Populations also extend for considerable distances inland in regions with enough moisture to support suitable woodlands. The koalas of South Australia were largely exterminated during the early part of the 20th century, but the state has since been repopulated with Victorian stock. The koala is not found in Tasmania or Western AustraliaSony VAIO PCG-8131L battery.

Names

The word koala comes from the Dharuk gula. Although the vowel /u/ was originally written in the English orthography as "oo" (in spellings such as coola or koolah), it was changed to "oa" possibly due to an error.[6] The word is erroneously said to mean "doesn't drink".[6]

The scientific name of the koala's genus, Phascolarctos, is derived from Greek phaskolos "pouch" and arktos "bear". Its species name, cinereus, is Latin and means "ash-coloured".Sony VAIO PCG-81312L battery

Although the koala is not a bear, English-speaking settlers from the late 18th century first called it koala bear due to its similarity in appearance to bears. Although taxonomically incorrect, the name koala bear is still in use today outside Australia[8] – its use is discouraged because of the inaccuracy in the name. Other descriptive English names based on "bear" have included monkey bear, native bear, and tree-bear. Sony VAIO PCG-81214L battery

Variation

A Southern koala on Kangaroo Island, not native to the island

Although three subspecies have been described, these are arbitrary selections from a cline and are not generally accepted as valid. Following Bergmann's Rule, individuals from the southern cooler climates are larger.

A typical Victorian koala (formerly P. cinereus victor) has longer, thicker fur; is a darker, softer grey, often with chocolate-brown highlights on the back and forearms; and has a more prominently light-coloured ventral side and fluffy white ear tuftsSony VAIO PCG-81115L battery. Typical and New South Wales koala weights are 12 kg (26 lb) for males and 8.5 kg (19 lb) for females. In tropical and sub-tropical Queensland, however, the koala is smaller (at around 6.5 kg (14 lb) for an average male and just over 5 kg (11 lb) for an average female); a lighter often rather scruffy grey in colour; and has shorter, thinner fur. In Queensland, the koala was previously classified as the subspecies P. cinereus adustusSony VAIO PCG-81114L battery, and the intermediate forms in New South Wales as P. cinereus cinereus. A fourth variation, though not technically a subspecies, is the "golden koala", which has a slight golden tinge to the fur as a result of an absence of the melanin pigment that produces albinism in most other mammalian species. The variation from one form to another is continuous and there are substantial differences between individual koalas in any given region such as hair colourSony VAIO PCG-81113L battery. Koalas may also have white fur in rare cases due to a recessive gene.

The origins of the koala are unclear, although almost certainly they descended from terrestrial wombat-like animals. Koala fossils are quite rare, but some have been found in northern Australia dating to 20 million years ago. During this time, the northern half of Australia was rainforest. The koala did not specialise in a diet of eucalypts until the climate cooled and eucalypt forests grew in the place of rainforestsSony VAIO PCG-7142L battery. The fossil record indicates that before 50,000 years ago, giant koalas inhabited the southern regions of Australia. The koala fills the same ecological role as the sloths of South America.

Physical description

The koala is broadly similar in appearance to the wombat (its closest living relative),[1] but has a thicker coat, much larger ears, and longer limbs. The koala has large, sharp claws to assist with climbing tree trunks. Weight varies from about 14 kg (31 lb) for a large southern male, to about 5 kg (11 lb) for a small northern femaleSony VAIO PCG-7141L battery. The koala's five fingers include two opposable thumbs, providing better gripping ability. The first two fingers are positioned in apposition on the front paws, and the first three fingers for the hind paws.[13] The koala is one of the few mammals (other than primates) that have fingerprints. Koala fingerprints are similar to human fingerprints; even with an electron microscopeSony VAIO PCG-71111L battery, it can be quite difficult to distinguish between the two.[14] The teeth of the koala are adapted to their herbivorous diet, and are similar to those of other diprotodont marsupials, such as kangaroos and wombats. They have sharp incisors to clip leaves at the front of the mouth, separated from the grinding cheek teeth by a wide diastema. The dental formula for koalas is

The male koala, like many marsupials, has a bifurcated penisSony VAIO PCG-61411L battery. The female has two lateral vaginas and two separate uteri, which is common to all marsupials.[15]

Koalas walk on all four legs when walking on the ground, joey clinging to the back

The brain in the ancestors of the modern koala once filled the whole cranial cavity, but has become drastically reduced in the present species, a degeneration scientists suspect is an adaptation to a diet low in energy.[16] One of the smallest in marsupials with no more than 0.2% of its body weight,[17] about 40% of the cranial cavity is filled with cerebrospinal fluidSony VAIO PCG-61112L battery, while the brain's two cerebral hemispheres are like "a pair of shrivelled walnut halves on top of the brain stem, in contact neither with each other nor the bones of the skull. It is the only animal on Earth with such a strangely reduced brain."[18]

It is generally a silent, nocturnal animal, but males have a very loud advertising call that can be heard from almost a kilometre away during the breeding season. Sony VAIO PCG-61111L battery Females glean clues regarding a male's suitability as a mate from these calls, showing a preference for larger males.[22] When under stress, koalas may issue a loud cry, which has been reported as similar to that of a human baby.[23] There is little reliable information about the lifespan of the koala, but in captivity they have been observed to reach the age of 18 years. Sony VAIO PCG-5T4L battery

Life cycle

A young joey, preserved at Port Macquarie Koala Hospital

Baby koala on a mother's back

Females reach maturity at 2 to 3 years of age, males at 3 to 4 years. A healthy female koala can produce one young each year for about 12 years. Gestation is 35 days. Twins are very rare; the world's first confirmed identical twin koalas, named "Euca" and "Lyptus", were born at the University of Queensland in April 1999. Mating normally occurs between December and March, the Southern Hemisphere's summerSony VAIO PCG-5T3L battery.

A baby koala is referred to as a joey and is hairless, blind, and earless. At birth the joey, only 20 mm (0.79 in) long, crawls into the downward-facing pouch on the mother's belly (which is closed by a drawstring-like muscle that the mother can tighten at will) and attaches itself to one of the two teatsSony VAIO PCG-5T2L battery.

Young remain hidden in the pouch for about six months, feeding on only milk. During this time they grow ears, eyes, and fur. The joey then begins to explore outside of the pouch. At about this stage it begins to consume small quantities of the mother’s "pap" (formerly thought to be excrement, but now thought to come from the mother's cecum) in order to inoculate its gut with the microbes necessary to digest eucalypt leaves. Sony VAIO PCG-5S3L battery The joey will remain with its mother for another six months or so, riding on her back, and feeding on both milk and eucalypt leaves until weaning is complete at about 12 months of age. Young females disperse to nearby areas at that time; young males often stay in the mother's home range until they are two or three years oldSony VAIO PCG-5S2L battery.

Diet and behaviour

Koala with joey in pouch

The koala lives almost entirely on eucalypt leaves. This is likely to be an evolutionary adaptation that takes advantage of an otherwise unfilled ecological niche, since eucalypt leaves are low in protein, high in indigestible substances, and contain phenolic and terpene compounds that are toxic to most species. Like wombats and sloths, the koala has a very low metabolic rate for a mammal and rests motionless for about 16 to 18 hours a daySony VAIO PCG-5S1L battery, sleeping most of that time. Koalas can be aggressive towards each other, throwing a foreleg around their opponent and biting, though most aggressive behaviour is brief squabbles.[27] Handling koalas may cause them stress,[28] and the issue of aggression and stress from handling is a political issue in Australia. Sony VAIO PCG-5R2L battery

Koalas spend about three of their five active hours eating. Feeding occurs at any time of day, but usually at night. Koalas eat an average of 500 g (18 oz) of eucalypt leaves each day, chewing them with powerful jaws to a very fine paste before swallowing. The liver deactivates the toxic components ready for excretion, and the hind gut (especially the cecum) is greatly enlarged to extract the maximum amount of nutrient from the poor quality dietSony VAIO PCG-5R1L battery. Much of this is done through bacterial fermentation: while young are being weaned, the mother passes these essential digestive aids on to her offspring.

A koala eating eucalyptus

The koala will eat the leaves of a wide range of eucalypts, and occasionally even some non-eucalypt species such as Acacia, Leptospermum, and Melaleuca. It has firm preferences for particular varieties of eucalypt and these preferences vary from one region to anotherSony VAIO PCG-5P4L battery: in the south Manna Gum, Blue Gum, and Swamp Gum are favoured; Grey Gum and Tallowwood are important in the north, and the ubiquitous River Red Gum of the isolated seasonal swamps and watercourses that meander across the dry inland plains allows the koala to live in surprisingly arid areas. Many factors determine which of the 680 species of eucalypt trees the koala eatsSony VAIO PCG-5P2L battery. Among trees of their favourite species, however, the major factor that determines which individual trees the koala chooses is the concentration of a group of phenolic toxins called formylated phloroglucinol compounds.[31] Researches on koalas by keepers at 13 wildlife parks and zoos in New South Wales show that the most preferred group of Eucalyptus foliage had the lowest content of condensed tannins. Sony VAIO PCG-5N4L battery

Conservation status

Koala in tree, scratching & grooming

The Australian government currently lists the koala as a priority species for conservation status assessment.[33] Government estimates of the national koala population numbers in the hundreds of thousands, although other studies have estimated as few as 80,000 koalas left in the wild.[34] The Australian Koala Foundation in 2008 estimated there are around 100,000 koalas left in the wild. Sony VAIO PCG-5N2L battery

As with most native Australian animals, the koala cannot legally be kept as a pet in Australia or anywhere else. The only people who are permitted to keep koalas are wildlife carers and, occasionally, research scientists. These individuals are issued with special permits to care for koalas, but have to return them to the wild when they are either well enough or, in the case of joeys, old enough. Sony VAIO PCG-51513L battery

The IUCN lists the species as "Least Concern".[36]

In April 2012, it was announced that koalas in NSW, Queensland and the ACT will be classified as vulnerable under a protected listing by Federal Environment Minister of the Australian government Tony Burke.

The US government has declared the koala a threatened species.[41]

The koala inhabits four Australian states. Under state legislation, the species is listed asSony VAIO PCG-51511L battery:

Queensland – Listed as "vulnerable".

New South Wales – Listed as "vulnerable".

Australian Capital Territory – Listed as "vulnerable".

South Australia – classified as rare (although the population on Kangaroo Island is thriving).[42]

Victoria – The koala population in Victoria was considered large and thriving, according to an article which was last reviewed on 29 October 2007.[43]

The koala was hunted almost to extinction in the early 20th century,[44] largely for its fur. Millions of furs were traded to Europe and the United States, and the population has not fully recovered from such decimationsSony VAIO PCG-51412L battery. Extensive cullings occurred in Queensland in 1915, 1917, and again in 1919 when over one million koalas were killed with guns, poisons, and nooses.[45] The public outcry over the cullings was most likely the first wide-scale environmental issue that rallied Australians.[45] Despite the growing movement to protect native species, the poverty brought about by the drought of 1926–28 led to another 600,000 koalas being killed during a one-month open season in August 1927Sony VAIO PCG-51411L battery.

Today, habitat loss and the impacts of urbanisation (such as dog attacks and traffic accidents) are the leading threats to the survival of the koala. In recent years, some colonies have been hard hit by disease, especially chlamydia.[46] 2011 surveys in Queensland show that chlamydia has caused symptoms in at least 50 percent of the koala populationSony VAIO PCG-51312L battery. Chlamydia of koalas is not the same as the human form, but can cause blindness, respiratory infections to all koalas and infertility of female koalas. Moreover nearly all of the koalas in Queensland are infected with koala retrovirus which suppresses the koala's immune system and interferes with its ability to fight off chlamydia.[47] The koala requires large areas of healthy, connected forest and will travel long distances along tree corridors in search of new territory and matesSony VAIO PCG-51311L battery. The increasing human population of the coastal parts of the continent continues to cut these corridors through agricultural and residential development, forestry, and road-building, thereby marooning koala colonies in decreasing areas of bush. The long-term viability of the koala is therefore threatened by genetic weakness[citation needed] Sony VAIO PCG-51211L battery. The Australian Koala Foundation is the principal organisation dedicated to the conservation of the koala and its habitat, mapping 40,000 km2 (15,000 sq mi) of land for koala habitat and claiming strong evidence that wild koala populations are in serious decline throughout the species' natural range.[42] Local councils in growing urban areas with koala populations that have established or are in the process of establishing planning overlays and controls to preserve habitat for koalas include the Victorian councils of City of BallaratSony VAIO PCG-41112L battery, Macedon Ranges Shire[50] and Glenelg Hopkins Catchment Management Authority[49] as well as the Queensland councils of Moreton Bay Regional Council and Redland Shire Council.

Although the species covers a large area, only portions of koala habitat remain. Presently, many habitats are lost to weeds, clearance for agriculture, or carved up by developers. Other threats come from logging, poor management, attacks from feral and domestic animals, diseases, and roadsSony VAIO PCG-3A4L battery.

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