Elephant: Encyclopedia II - Elephant - Zoology

Elephant - Zoology

Elephant - African Elephant

Main articles: Savanna Elephant and Forest elephant

The mammals of the genus Loxodonta, often known collectively as African elephants, are found in several regions throughout the continent after which they are named. In recent years, Loxodonta has received the attention of the world because of its dwindling numbers. Today there are approximately 600,000 African elephants in the world. Some believe this represents a stable population and that measures to protect them are unnecessary. Others argue that while elephants are locally overabundant in certain areas, it is impossible to ignore the fact that the overall population has dropped by a staggering amount. As recently as 1979 there were an estimated 1.3 million African elephants. This decline is attributed primarily to poaching, or illegal hunting, and habitat loss.

African elephants are distinguished from Asians in several ways. The most noticeable difference is the ears. Africans' ears are much larger and are shaped like the continent of their origin. The African elephant is typically larger than the Asian and has a concave back. Both males and females have external tusks and are usually less hairy than their Asian cousins.

Until the late 20th century, scientists recognized one species of African elephants, Loxodonta africana, and two subspecies, or races, within the species. Recent DNA analysis has led scientists to reclassify the two races as distinct species.

Today, Loxodonta africana refers specifically to the Savanna Elephant, the largest of all the elephants. In fact, it is the largest land animal in the world, standing on average 13 feet (4 meters) at the shoulder and weighing approximately 15,400 pounds (7,000 kilograms). Most often, Savanna Elephants are found in open grasslands, marshes, and lakeshores. They range over most of Africa south of the Sahara Desert.

The other, less numerous species is the Forest Elephant, recently reclassified as Loxodonta cyclotis. Compared with the Savanna Elephant, its ears are usually smaller and rounder, and its tusks are also thinner and straighter. The Forest Elephant can weigh up to 10,000 lb (4,500 kg) and stand about 10 feet (3 m) tall. Much less is known about these animals than their savanna cousins because environmental and political obstacles make them very difficult to study. Normally they inhabit the dense forests of central and western Africa, though occasionally they do inhabit the edges of forests and overlap territories with bush elephants.

Elephant - Asian Elephant

Today scientists estimate the world population of Asian elephants, or Elephas maximus, to be approximately 40,000, less than one-tenth the number of African elephants. Perhaps the Asian elephants' decline has been less noticeable because it has been more gradual. The causes of this decline are much the same as that of the African.

As with the Loxodonta, there are distinct subspecies of Elephas maximus. In general, the Asian elephant is smaller than the African. It has smaller ears, shaped like the subcontinent of India, and typically only the males have large external tusks. An Asian elephant can also be distinguished by the large bulges of depigmentation on the skin.

The first subspecies is the Sri Lankan Asian elephant [www.geocities.com/RainForest/8298] (Elephas maximus maximus). Found only on the island of Sri Lanka, a small country off the southeast coast of India, it is the largest of the Asians. There are an estimated total of only 3,000-4,500 members of this subspecies left today in the wild, although no accurate census has been carried out in the recent past. Large males can weigh upward to 12,000 pounds and stand over 11 feet tall. Sri Lankan males have very large cranial bulges, and both sexes have more areas of depigmentation than are found in the other Asians. typically their ears, face, trunk, and belly have large concentrations of pink-speckled skin. There is an Orphanage for Elephants in Pinnawala Sri Lanka, which gives shelter to disabled, injured Elephants. This program plays a large role to protect the Sri Lankan Elephant from extinction.

Another subspecies, the mainland Asian elephant (Elephas maximus indicus) makes up the bulk of the Asian elephant population. Numbering approximately 36,000, these elephants are lighter gray in colour, with depigmentation only on the ears and trunk. Large males will ordinarily weigh only about 11,000 pounds but are as tall as the Sri Lankan. The mainland Asian can be found in 12 Asian countries, from india to Indonesia. It prefers forested areas and transitional zones, between forests and grasslands, where greater food variety is available.

The smallest of all the elephants is the Sumatran Asian elephant (Elephas maximus sumatranus). Population estimates for this group range from 33,000 to 53,000 individuals. It is very light gray and has less depigmentation than the other Asians, with pink spots only on the ears. Mature Sumatrans will usually only measure about 10 feet at the shoulder and weigh less than nine thousand pounds. An enormous animal nonetheless, it is considerably smaller than its other Asian (and African) cousins and exists only on the island of Sumatra, usually in forested regions and partially wooded habitats.

Elephant - Body characteristics

Elephant social life, in many ways, revolves around breeding and raising of the calves. A female will usually be ready to breed around the age of thirteen, at which time she will seek out the most "fit" male to mate with. The word fitness, in an ecological sense, means the animal best suited to survive in its environment and pass on its genes. Females want to breed with the bigger, stronger, and, most importantly, older males. In this way, they are assuring that their offspring will have the best possible chance of survival. After a twenty-two-month pregnancy, the mother will give birth to a calf that will weigh about 250 lbs. and stand over 2½ feet tall. Elephants have a very long childhood. They are born with fewer survival instincts than many other animals. Instead, they must rely on their elders to teach them the things they need to know. The ability to pass on information and knowledge to their young has always been a major asset in the elephant's struggle to survive. Today, however, the pressures humans have put on the wild elephant populations, from poaching to habitat destruction, mean that the elderly often die at a younger age, leaving fewer teachers for the young. All members of the tightly knit female group participate in the care and protection of the young. Since everyone in these herds is related, there is never a shortage of baby-sitters. In fact, a new calf is usually the center of attention for all herd members. All the adults and most of the other young will gather around the newborn, touching and caressing it with their trunks. The baby is born nearly blind and at first relies, almost completely, on its trunk to discover the world around it.

After the initial excitement dies down, the mother will usually select several full-time baby-sitters, or "allomothers", from her group. According to Cynthia Moss, a well-known researcher, these allomothes will help in all aspects of raising the calf. They walk with the young as the herd travels, helping the calves along if they fall or get stuck in the mud. The more allomothers a baby has, the more free time its mother has to feed herself. Providing a calf with nutritious milk means the mother has to eat more nutritious food herself. So, the more allomothers, the better the calf's chances of survival.

The proboscis, or trunk, is perhaps the elephant's most distinctive feature. It is a fusion of the nose and upper lip, elongated and specialized to become the elephant's most important and versatile appendage. The trunk is basically used to manipulate objects. To facilitate this, African elephants are equipped with two fingerlike projections at the tip of their trunk, while Asians have only one. According to biologists, the elephant's trunk is said to have over forty thousand individual muscles in it, making it sensitive enough to pick up a single blade of grass, yet strong enough to rip the branches off a tree. Most herbivores (plant eaters, like the elephant) are adapted with teeth for cutting and tearing off plant materials. However, except for the very young or infirm, elephants always use their trunks to tear up their food and then place it in their mouth. They will graze on grass or reach up into trees to grasp leaves, fruit, or entire branches. If the desired food item is too high up, the elephant will wrap its trunk around the tree or branch and shake its food loose or sometimes simply knock the tree down altogether. The trunk is also used for drinking. Elephants suck water up into the trunk (up to fifteen quarts [14.2 liters] at a time) and then blow it into their mouth. Elephants also inhale water to spray on their body during bathing. On top of this watery coating, the animal will then spray dirt and mud, which act as a protective sunscreen. This appendage also plays a key role in many social interactions. Familiar elephants will greet each other by entwining their trunks, much like a handshake. They also use them while play-wrestling, caressing during courtship, and for dominance displays - a raised trunk can be a warning or threat, while a lowered trunk can be a sign of submission. Elephants can defend themselves very well by flailing their trunk at unwanted intruders or by grasping and flinging them. An elephant also relies on its trunk for its highly developed sense of smell. Raising the trunk up in the air and swiveling it from side to side, like a periscope, it can determine the location of friends, enemies, and food sources.

The tusks of an elephant are upper incisors that are continuously growing. An adult male's tusks will grow about seven inches a year. Tusks are indispensable to an elephant. They are used primarily to dig for water, salt, and roots; to debark trees, in order to get at the tasty pulp inside; and to move downed trees and branches when clearing a path. In addition, they are used for marking trees to establish territory and occasionally as weapons. Like humans who are typically right- or left-handed, elephants are usually right- and left-tusked. The dominant tusk, called the master tusk, is generally shorter and more rounded at the tip from wear. Both male and female African elephants have large, impressive tusks that can reach over ten feet in length and weigh over two hundred pounds. In the Asian species, only the males have large tusks. Female Asians have tusks which are very small or absent altogether. Asian males can have tusks as long as the much larger Africans, but they are usually much slimmer and lighter (the heaviest recorded was only 86 pounds). the tusk of both species is mostly made of calcium and phosphate. As a piece of living tissue, it is relatively soft (compared with other minerals such as rock), and the tusk, also known as ivory, is strongly favoured by artisans for its carvability. The desire for elephant ivory has been one of the major factors in the dramatic decline of the world's elephant population.

Elephants' teeth are very different from those of most other mammals. Over their lives they have 26 teeth, including two upper incisors (tusks), 12 premolars, and 12 molars. Unlike most mammals, which grow baby teeth and then replace them with a permanent set of adult teeth, elephants have cycles of tooth rotation throughout their entire life. After one year the tusks are permanent, but the other teeth are replaced six times in an elephant's life. The teeth don't emerge from the jaws vertically like humans' do with new teeth replacing old ones from above or below. Instead, they have a horizontal progression, like a conveyor belt. New teeth grow in at the back of the mouth, pushing older teeth toward the front, where they become brittle and fall out, making room for more teeth. When an elephant becomes very old, the last set of teeth become brittle, and it must rely on softer foods to chew. Very elderly elephants often spend their final years exclusively in marshy areas where they can feed on soft wet grasses. Eventually, when the final teeth fall out, the animal will be unable to eat and will die. However, as more habitat is destroyed, the elephants' living space becomes smaller and smaller; the elderly no longer have the opportunity to roam in search of more appropriate food and will, consequently, die of starvation at an earlier age.

Another name for an elephant is pachyderm, which means "thick skin". An elephant's skin is extremely tough around most parts of its body. However, the skin around the mouth and inside of the ear is paper thin. Normally, the skin of an Asian is covered with more hair than its African counterpart. This is most noticeable in the young. Asian calves are usually covered with a thick coat of brownish red fuzz. As they get older, this hair darkens and becomes more sparse, but it will always remain on their heads and tails.

Both species of elephants are typically grayish in colour, but the Africans very often appear brown or reddish from wallowing in mud holes of coloured soil. Wallowing is actually a very important behaviour in elephant society. Not only is it important for socialization, but the mud acts as a sunscreen, protecting their skin from harsh ultraviolet radiation. Though tough, an elephant's skin is very sensitive. Without regular mud baths to protect it from burning, as well as from insect bites and moisture loss, an elephant's skin would suffer serious damage. After bathing, the elephant will usually use its trunk to blow dirt on its body to help dry and bake on its new protective coat. As elephants are limited to smaller and smaller areas, there is less water available, and local herds will often come too close over the right to use these limited resources.

Wallowing also aids the skin in regulating body temperatures. Elephants spend every day fighting an uphill battle to stay cool. They have a very difficult time releasing heat through the skin because, in proportion to their body size, they have very little of it. The ratio of an elephant's mass to the surface area of its skin is many times that of a human. Elephants have even been observed lifting up their legs to expose the soles of their feet, presumably in an effort to expose more skin to the air. Since wild elephants live in very hot climates, they must have other means of getting rid of excess heat.

The large flapping ears of an elephant are also very important for temperature regulation. Elephant ears are made of a very thin layer of skin stretched over cartilage and a rich network of blood vessels. On hot days, elephants will flap their ears constantly, creating a slight breeze. This breeze cools the surface blood vessels, and then the cooler blood gets circulated to the rest of the animal's body. The hot blood entering the ears can be cooled as much as ten degrees Fahrenheit before returning to the body. Differences in the ear sizes of African and Asian elephants can be explained, in part, by their geographical distribution. Africans originated and stayed near the equator, where it is warmer. Therefore, they have bigger ears. Asians live farther north, in slightly cooler climates, and thus have smaller ears.

The ears are also used in certain displays of aggression and during the males' mating period. If an elephant wants to intimidate a predator or rival, it will spread its ears out wide to make itself look more massive and imposing. During the breeding season, males give off an odor from a gland located behind their eyes. Joyce Poole, a well-known elephant researcher, has theorized that the males will fan their ears in an effort to help propel this "elephant cologne" great distances.

Walking at a normal pace an elephant covers about 2 to 4 miles an hour (3 to 6 km/h) but they can reach 24 miles an hour (40 km/h) at full speed.

Elephant - Evolution

Although the fossil evidence is uncertain, some scientists believe there is genetic evidence that the elephant family shares distant ancestry with the Sirenians (sea cows) and the hyraxes. In the distant past, members of the hyrax family grew to large sizes, and it seems likely that the common ancestor of all three modern families was some kind of amphibious hyracoid. One theory suggests that these animals spent most of their time under water, using their trunks like snorkels for breathing. Modern elephants have retained this ability and are known to swim in that manner for up to 6 hours and 50 km.

In the past, there was a much wider variety of elephant genera, including the mammoths, stegodons and deinotheria.

Elephant - Varieties

It has long been known that the African and Asian elephants are separate species. African elephants tend to be larger than the Asian species (up to 4 m high and 7500 kg) and have bigger ears (which are rich in veins and thought to help in cooling off the blood in the hotter African climate). Male and female African elephants have long tusks, while male and female Asian Elephants have shorter tusks, with tusks in females being almost non-existent. African elephants have a dipped back, smooth forehead and two "fingers" at the tip of their trunks, as compared with the Asian species which have an arched back, two humps on the forehead and have only one "finger" at the tip of their trunks.

There are two populations of African elephants, Savannah and Forest, and recent genetic studies have led to a reclassification of these as separate species, the forest population now being called Loxodonta cyclotis, and the Savannah (or Bush) population termed Loxodonta africana. This reclassification has important implications for conservation, because it means where there were thought to be two small populations of a single endangered species, there may in fact be two separate species, each of which is even more severely endangered. There's also a potential danger in that if the forest elephant isn't explicitly listed as an endangered species, poachers and smugglers might thus be able to evade the law forbidding trade in endangered animals and their body parts.

The Forest elephant and the Savannah elephant can hybridise successfully, though their preference for different terrains reduces the opportunities to hybridise. Many captive African elephants are probably generic African elephants as the recognition of separate species has occurred relatively recently.

Although hybrids between different animal genera are usually impossible, in 1978, an Asian elephant cow gave birth to a hybrid calf sired by an African elephant bull (the old terms are used here as this pre-dates current classifications). The pair had mated several times, but pregnancy was believed to be impossible. "Motty", the resulting hybrid male calf, had an African elephant's cheek, ears (large with pointed lobes) and legs (longer and slimmer), but the toenail numbers, (5 front, 4 hind) and the single trunk finger of an Asian elephant. The wrinkled trunk was like an African elephant. The forehead was sloping with one dome and two smaller domes behind it. The body was African in type, but had an Asian-type centre hump and an African-type rear hump. Sadly the calf died of infection 12 days later. It is preserved as a mounted specimen at the British Natural History Museum, London. There are unconfirmed rumours of three other hybrid elephants born in zoos or circuses, all of were said to have been deformed and did not survive.

Elephant - Diet

Elephants are herbivores, spending 16 hours a day collecting plant food. Their diet is at least 50% grasses, supplemented with leaves, twigs, bark, roots, and small amounts of fruits, seeds and flowers. Because elephants only use 40% of what they eat they have to make up for their digestive system's lack of efficiency in volume. An adult elephant can consume 300 to 600 pounds (140 to 270 kg) of food a day. 60% of that food leaves the elephant's body undigested.

Elephant - Social behavior

Elephants live in a very structured social order. The social lives of male and female elephants are very different. the females spend their entire lives in tightly knit family groups made up of mothers, daughters, sisters, and aunts. These groups are led by the eldest female, or matriarch. Adult males, on the other hand, live mostly solitary lives.

The social circle of the female elephant does not end with the small family unit. In addition to encountering the local males that live on the fringes of one or more groups, the female's life also involves interaction with other families, clans, and subpopulations. Most immediate family groups range from five to fifteen adults, as well as a number of immature males and females. When a group gets too big, a few of the elder daughters will break off and form their own small group. They remain very aware of which local herds are relatives and which are not.

The life of the adult male is very different. As he gets older, he begins to spend more time at the edge of the herd, gradually going off on his own for hours or days at a time. Eventually, days become weeks, and somewhere around the age of fourteen, the mature male, or bull, sets out from his natal group for good. While males do live primarily solitary, lives, they will occasionally form loose associations with other males. These groups are called bachelor herds. The males spend much more time than the females fighting for dominance with each other. Only the most dominant males will be permitted to breed with cycling females. The less dominant ones must wait their turn. It is usually the older bulls, forty to fifty years old, that do most of the breeding. The dominance battles between males can look very fierce, but typically they inflict very little injury. Most of the bouts are in the form of aggressive displays and bluffs. Ordinarily, the smaller, younger, and less confident animal will back off before any real damage can be done. However, during the breeding season, the battles can get extremely aggressive, and the occasional elephant is injured. During this season, known as musth, a bull will fight with almost any other male it encounters, and it will spend most of its time hovering around the female herds, trying to find a receptive mate.

Elephant - Reproduction

• Females (cows) reach sexual maturity at around 9-12 years of age and become pregnant for the first time, on average, around age 13. They can reproduce until ages 55-60.

• Females give birth at intervals of about every 5 years.

• An elephant's gestation period lasts about 22 months (630-660 days), the longest gestation period of any mammal, after which one calf typically is born. Twins are rare.

• Labor ranges in length from 5 minutes to 60 hours. The average length of labor is 11 hours.

• At birth, calves weigh around 90-115 kilograms (200-250 pounds), and they gain 1 kilogram (2-2.5 pounds) a day.

• In the wild, the mother is accompanied by other adult females (aunts) that protect the young.

• In the wild, baby elephants are raised and nurtured by the whole family group, practically from the moment they are born.

Elephant - Motherhood and calf rearing

• The first sound a newborn calf usually makes is a sneezing or snorting sound to clear its nasal passages of fluids. (In the first few minutes after a captive birth, the keepers must monitor the calf closely for the first sound or movement. Whichever happens first, the mother typically responds to her new baby with surprise and excitement.)

• With the help of its mother, a newborn calf usually struggles to its feet within 30 minutes of birth. For support, it will often lean on its mother's legs.

• A newborn calf usually stands within one hour and is strong enough to follow its mother in a slow-moving herd within a few days.

• Unlike most mammals, female elephants have a single pair of mammary glands located just behind the front legs. When born, a calf is about 3 feet (90 cm) high, just tall enough to reach its mother's nipples.

• A calf suckles with its mouth, not its trunk, which has no muscle tone. To clear the way to its mouth so it can suckle, the calf will flop its trunk onto its forehead.

• A newborn calf suckles for only a few minutes at a time but will suckle many times per day, consuming up to 11 litres (3 gallons) of milk in a single day.

• A calf may nurse for up to 2 years of age or older. Complete weaning depends on the disposition of the mother, the amount of available milk, and the arrival of another calf.

• Newborn calves learn primarily by observing adults, not from natural instinct. For example, a calf learns how to use its trunk by watching older elephants using their trunks.

• It takes several months for a calf to control the use of its trunk. This can be observed as the calf trips over its trunk or as the trunk wiggles like a rubbery object when the calf shakes its head.

Adapted from the Wikipedia article "Zoology", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki