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Friday, July 9, 2010
CHARACTERICS AND BEHAVIOR
Not Just a Flash in the Pan: A zebra can travel at a top speed of fifty-five kilometers per hour, slower than a horse. However, it has much greater stamina. During the course of a day the plains zebra can walk around forty kilometers (from its herd, and back again in the evening)
Family Ties: There are four species, as well as several subspecies. Zebra populations vary a great deal, and the relationships between and the taxonomic status of several of the subspecies are unclear.
The Plains zebra (Equus quagga, formerly Equus burchelli) is the most common, and has or had about five 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 burchelli), 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 endangered.
Grevy's Zebra (Equus grevyi) is the largest type, with an erect mane, and a long, narrow head making it appear rather mule-like. It is an inhabitant of the semi-arid grasslands of Ethiopia, Somalia, and northern Kenya. The Grevy's zebra is one of the rarest species of zebra around today, and is classified as endangered.
Plains Zebras are mid-sized and thick-bodied with relatively short legs. Adults of both sexes stand about 1.4 meters high at the shoulder, are approximately 2.3 meters long, and weigh about 230 kg. Like all zebras, they are boldly striped in black and white and no two individuals look exactly alike. All have vertical stripes on the forepart of the body, which tend towards the horizontal on the hindquarters. The northern species have narrower and more defined striping; southern populations have varied but lesser amounts of striping on the underparts, the legs and the hindquarters.
Striped and Social: Plains zebras are highly social and usually form small family groups consisting of a single stallion, one, two, or several mares, and their recent offspring. Groups are permanent, and group size tends to vary with habitat: in poor country the groups are small. From time to time, Plains zebra families group together into large herds, both with one another and with other grazing species, notably Blue wildebeests. Unlike many of the large ungulates of Africa, Plains zebras prefer but do not require short grass to graze on. In consequence, they range more widely than many other species, even into woodlands, and they are often the first grazing species to appear in a well-vegetated area.
Only after zebras have cropped and trampled the long grasses do wildebeests and gazelles move in. Nevertheless, for protection from predators, Plains zebras retreat into open areas with good visibility at night time, and take it in turns standing watch. They eat a wide range of different grasses, preferring young, fresh growth where available, and also browse on leaves and shoots from time to time.
Mountain Zebras are native to South West Africa and are found in dry, stony, mountain and hill habitats. Its diet is tufted grass, bark, leaves, fruit and roots. Zebras' dazzling stripes may be a signaling system for the herd and may also be useful in confusing predators
The Grevy's Zebra (Equus grevyi), sometimes known as the Imperial Zebra, is the largest species of zebra. It is found in the wild in Kenya, Somalia, and Ethiopia, and is considered endangered, partly due to hunting for its skin, which fetches a high price on the world market. Compared to other zebras, it is tall, has large ears, and its stripes are narrower. The species is named after Jules Grévy, a president of France, who, in the 1880s, was given one by the government of Abyssinia.
Sizes and Scales: The Grevy's zebra is the largest of all wild equines. It is 2.5-3 m from head to tail with a 38-75 cm tail, and stands 1.25-1.6 m high at the shoulder. Males weigh 380-450 kg, and females 350-400 kg. The stripes are narrow and close-set, being broader on the neck, and they extend to the hooves. The belly and the area around the base of the tail lack stripes.
The ears are very large, rounded, and conical. The head is large, long, and narrow, particularly mule-like in appearance. The mane is tall and erect; juveniles having a mane extending the length of the back.
The Donkey Connection: Grevy's zebra is similar to the asses in many ways. Behaviorally, for example, it has a social system characterized by small groups of adults associated for short time periods of a few months. Adult males spend their time mostly alone in territories of 2-12 km², which is considerably smaller than the territories of the wild asses.
The territories are marked by dung piles and females within the territory mate solely with the resident male. Small bachelor herds are known. This social structure is well-adapted for the dry and arid scrubland and plains that Grevy's zebra primarily inhabits, less for the more lush habitats used by the other zebras.
Fighting for Females: Like all zebras and asses, Grevy's zebra males fight amongst themselves over territory and females. The Grevy's is vocal during fights (an asinine characteristic), braying loudly. Otherwise, the Grevy's communicates over long distances.
Just the Facts: The Grevy's zebra lives 10-25 years and eats grasses and other plants. Gestation lasts 350-400 days, with a single foal being born. Predators of Grevy's zebra include hunters and wild dogs native to the area. Most captive zebras in zoos are Grevy's Zebras.
Why Stripes? Originally, most zoologists assumed that zebras' stripes acted as a camouflage mechanism, while others believed them to play a role in social interactions, with slight variations of the pattern allowing the animals to distinguish between individuals. A more recent theory, supported by experiment, posits that the disruptive coloration is an effective means of confusing the visual system of the blood-sucking tsetse fly.
ARTICLE AFRICAN ELEPHANTS
Loxodonta is a genus in Elephantidae, the family of elephants and is divided into two species.
The African Bush Elephant (Loxodonta africana) is the better-known and larger of the two species of African elephants. Both it and the African Forest Elephant were previously classified as a single species, known simply as the African Elephant. It is also known as the Bush Elephant or Savanna Elephant.
Sizes and Scales: The African Bush Elephant is the largest land dwelling animal, normally reaches 6 to 7.3 m (20 to 24 ft) in length and 3 to 3.5 meters in height, although a 4-meter elephant, the body of which is mounted in the rotunda of the National Museum of Natural History in Washington, D.C., was discovered in Angola in 1955.
Big and Brisk: Weighing between 7,000 and 10,000 kg (15,000-22,000 lb), it is the largest land animal in the world. It moves at a rate of 6 km/h, but it can reach a top speed of 40 km/h when scared or upset.
Thick Skinned: The animal is protected by a heavy but flexible layer of gray-brown skin, dotted with mostly undeveloped patches of hair and long, black hair at the tip of its tail. Its back feet have three toes that form a hoof, while the number of toes on the front feet have varied between four and five, in different instances. The front is smoother and less convex than that of the Asian Elephant.
Nose + Lip = Trunk: The trunk is the most characteristic feature of the African Bush Elephant. It is formed by the fusion and elongation of the nose and upper lip, forming a flexible and strong organ made purely of muscle.
Intellectual Giants? A recent report states that African elephants are able to use seismic vibrations at infrasound frequencies for communication. The African Bush Elephant is a notably intelligent animal. In fact, experiments about reasoning and learning applied on them show that they are the smartest ungulates together with their Asian cousins. This is mostly due to their large brain.
African & Asian: Differences between the African Bush Elephant and the African Forest Elephant include the Forest Elephant's long, narrow mandible (the African Bush Elephant's is short and wide), its rounded ears (an African Bush Elephant's ears are more pointed), different tusks, and considerably smaller size. The Male African Forest Elephant rarely exceed 2.5 meters (8 feet) in height, while the African Bush Elephant is usually over 3 meters (just under 10 feet) and sometimes almost 4 meters (13 feet) tall.
What's on the menu? African elephants are herbivorous. The diet of the African Bush Elephant varies according to its habitat; elephants living in forests, partial deserts, and grasslands all eat different proportions of herbs and tree or shrubbery leaves.
Chew on this! In order to break down the plants they consume, the African Bush Elephant has four large molars, two in each mandible of the jaw. Each of these molars is 10 cm wide and 30 cm long. Over time, these molars are worn away and new ones are grown to replace them as the elephant ages. Around the age of 15 their milk teeth are replaced by new ones that last until the age of 30, and then by another set which wear off past the age of 40, being replaced by the last set of teeth that last approximately until the age of 65–70. Not much later, the animal dies of starvation from not being able to feed correctly. There are known cases of over 80 year old specimens in captivity.
Big Appetite: These animals typically ingest an average of 225 kg of vegetable matter daily, which is defecated without being fully digested. That, combined with the long distances that they can cover daily in search of more food, contributes notably to the dispersion of many plant seeds that germinate in the middle of a nutrient-filled feces mound. In their feeding-oriented whereabouts, elephants rip apart all kind of plants, and knock down trees with the tusks if they are not able to reach the tree leaves not even standing up straight, as actual living bulldozers. It can be said that they carry devastation with them. That causes deep trouble for other species and to the elephants themselves in national parks where there is overpopulation, so that managers of overpopulated parks often contact other parks with fewer specimens to transfer excess individuals.
Thirst Quencher: Elephants also drink great quantities of water, over 190 liters per day.
Mothers Rule: Herds are made up of related females and their younglings of assorted ages, directed by the eldest female, called the matriarch. Infrequently, an adult male goes with them, but those usually leave the pack when reaching adolescence to form herds with other elephants of the same age. Later, they spread out, carrying out a lonely life, approaching the female herds only during the mating season. Nevertheless, elephants don't get too far from their families and recognize them when re-encountered. Sometimes, several female herds can blend for a period of time, reaching even hundreds of individuals.
Herd Is Where The Heart Is:
The matriarch is the one who decides the route and shows to each other member of the herd all the water sources she knows, which the rest will memorize in the future.
The relations among the members of the herd is very tight; when a female gives birth to a baby the rest go to acknowledge it by touching her with the trunk; and when an old elephant dies the rest of the herd will stay by the corpse for a while.
The famous elephant graveyards are a myth, but it is true that these animals can recognize a carcass of its species when they find one during their trips, and even if it is a stranger, they form around it and sometimes they even touch its forehead with their trunk.
Killing Rhinos: Some African Bush Elephants will attack and kill rhinoceroses. This behavior, when it occurs, is mostly observed with younger adult male elephants who have come into musth prematurely.
Natural Predators: The adult African Bush Elephant lacks natural predators thanks to its great size, but the calves (especially the newborn) are vulnerable to lion, leopard, crocodile, and, more rarely, hyena attacks. Adult females of a group will attack approaching predators. Predation, as well as drought, contribute significantly to infant mortality.
Human Predators: Humans are the elephant's major predator. Elephants have been hunted for meat as well as the rest of the body, including skin, bones, and tusks. Elephant trophy-hunting increased in the 19th and 20th centuries, when tourism and plantations increasingly attracted sport hunters.
In 1989, hunting of the African elephant and ivory trading were forbidden, after the elephant population fell from several million at the beginning of the 20th century to fewer than 700,000. The population of African elephants was halved during the 1980s. Scientists then estimated that, if no protective measures were taken, the wild elephant would be extinct by 1995. The protection that the elephant now receives has been partially successful, but despite increasingly severe penalties imposed by governments against illegal hunting, poaching is still common. CITES still considers this species as threatened with extinction.
Birds and Bees: Mating for a African Bush Elephant happens when the female feels ready, an event that can occur anytime during the year. When she is ready, she starts emitting infrasounds that attract the males, sometimes many kilometers away.
The adult males start arriving to the herd during the following days and begin fighting head-to-head between them, causing some injuries and even broken tusks. The female shows her acceptance of the victor by rubbing her body against his. They mate, and then both go their own way.
Incredibly Long Pregnancy: After 22 months of gestation (the longest among mammals), the female gives birth to a single 90cm-high calf which weighs more than 100 kg.
The baby feeds on the mothers milk until the age of 5, but also eats solid food from as early as 6 months old. Just a few days after birth the calf can follow the herd by foot, and so the herd resumes its course.
Classification Confusion: Until recently, it was thought that the so-called African Forest Elephant (Loxodonta cyclotis) was simply a subspecies of the African Bush Elephant (Loxodonta africana).
DNA testing has now shown that there are in fact three extant elephant species: the two African types (formerly considered to be separate populations of a single species, the African Elephant) and the South Asian species, known as the Indian or Asian Elephant. The North African elephant of Hannibal fame was a now-extinct fourth species or a subspecies of the Forest Elephant (Loxodonta (africana) pharaoensis); it disappeared around the 1st or 2nd century CE.
The disputed Pygmy Elephants of the Congo basin, often assumed to be a separate species (Loxodonta pumilio) by cryptozoologists, are probably Forest Elephants whose diminutive size and/or early maturity is due to environmental conditions.
Late in the 20th century, conservation workers established a DNA identification system to trace the origin of poached ivory. It had long been known that the ivory of the African Forest Elephant was particularly hard, with a pinkish tinge, and straight (whereas that of the African Bush Elephant is curved). The DNA tests, however, indicated that the two populations were much more different than originally thought—indeed, in its genetic makeup, the African Forest Elephant is almost two-thirds as distinct from the African Bush Elephant as the Asian Elephant is.
ARTICLE AARDVARK
The Aardvark (Orycteropus afer) is a medium-sized mammal native to Africa. The name comes from the Afrikaans/Dutch for "earth pig" (aarde earth, varken pig), because early settlers from Europe thought it resembled a pig. However, the Aardvark is not closely related to pigs.
Chew on This: The most distinctive charactristic of aardvarks is their teeth. Instead of having a pulp cavities, aardvark teeth have lots of thin tubes of dentine, each containing pulp and held together by cementum. The teeth have no enamel coating and are worn away and regrow continuously. In adults, the only teeth are the molars at the back of the jaw.
Appearance: The Aardvark is only vaguely pig-like; the body is stout with an arched back; the limbs are of moderate length. The ears are disproportionately long and the tail very thick at the base with a gradual taper. The greatly elongated head is set on a short, thick neck, and at the end of the snout is a disk in which the nostrils open. The mouth is typical of species that feed on termites: small and tubular. The Aardvark has a long, thin, protrusible tongue and elaborate structures supporting a keen sense of smell. The Aardvark is a pale yellowish gray in color, often stained reddish-brown by soil. The coat is thin and the animal's primary protection is its tough skin; the Aardvark has been known to sleep in a recently excavated ant nest, so well does it protect them.
Aardvark of Africa: The Aardvark is distributed across most of sub-Saharan Africa, and although killed by humans both for its flesh and for its teeth (which are used as decorations), does not appear to be threatened.
Insects for Dinner: The Aardvark is nocturnal and a solitary creature that feeds almost exclusively on ants and termites. An Aardvark emerges from its burrow in the late afternoon or shortly after sunset, and forages over a considerable home range, swinging its long nose from side to side to pick up the scent of food. When a concentration of ants or termites is found, the Aardvark digs into it with its powerful front legs, keeping its long ears upright to listen for predators, and takes up an astonishing number of insects with its long, sticky tongue—as many as 50,000 in one night has been recorded. It is an exceptionally fast digger, but otherwise moves rather slowly.
Burrow Park: Aside from digging out ants and termites, the Aardvark also excavates burrows to live in: temporary sites scattered around the home range as refuges, and the main burrow which is used for breeding.
Burrow Basics: Main burrows can be deep and extensive, have several entrances, and can be as much as 13 meters long. The Aardvark changes the layout of its home burrow regularly, and from time to time moves on and makes a new one. Only mothers and young share burrows.
Trivia:
* Aardvark is usually considered the first noun in the English dictionary.
* Arthur Read is a fictional aardvark (despite looking more like a mouse) with human-like traits. He is a book and television character created by Marc Brown.* Cerebus the Aardvark is a comic aardvark created by Canadian artist Dave Sim.
* Jason Webley, the musician, has a song about an aardvark.
* The Raccoons, a popular Canadian animated television show in the late 1980's, featured a pink, anti-environmentalist aardvark named Cyril Snear.
* Earlham College (Richmond, Indiana) is the only American liberal arts university, outside of zoological institutes, with a comprehensive concentration in the study of aardvarks.
* In the Pink Panther cartoon there was a character named the "Blue Aardvark". The Pink Panther represented innocence and un-fortune, The Blue Aardvark was unkind and ill-polite...
After a gestation period of 7 months, a single cub weighing around 2 kg is born, and is able to leave the burrow to accompany its mother after only two weeks. At six months of age it is digging its own burrows, but it will often remain with the mother until the next mating season. The Aardvarks can grow older than 20 years in captivity.
The Aardvark is the only surviving member of the family Orycteropodidae and of the order Tubulidentata. The Aardvark was originally placed in the same genus as the South American anteaters because of superficial similarities which, it is now known, are the result of convergent evolution, not common ancestry. For the same reason, Aardvarks bear a striking first-glance resemblance to the marsupial bilbies and Bandicoots of Australasia, which are not placental mammals at all. The Aardvark is now placed in its own genus, Orycteropus.
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