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Elephant
From
Wikipedia, the free encyclopedia
African Bush (Savannah) Elephant in Kenya.
Scientific classification
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Kingdom: |
Animalia |
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Phylum: |
Chordata |
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Subphylum: |
Vertebrata |
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Class: |
Mammalia |
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Order: |
Proboscidea |
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Superfamily: |
Elephantoidea |
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Family: |
Elephantidae |
Elephantidae (the elephants) is a family
of pachyderm, and the only remaining family in the order Proboscidea in the
class Mammalia. Elephantidae has three living species: the African Bush
Elephant, the African Forest Elephant (until recently known collectively as the
African Elephant), and the Asian Elephant (also known as the Indian Elephant).
Other species have become extinct since the last ice age, which ended about
10,000 years ago.
Elephants are mammals, and
the largest land animals alive today. The elephant's gestation period is 22
months, the longest of any land animal. At birth it is common for an elephant
calf to weigh 120 kg (265 lb). An elephant may live as long as 70 years,
sometimes longer. The largest elephant ever recorded was shot in Angola in
1956. It was male and weighed about 12,000 kg (26,400 lb),[1] with a
shoulder height of 4.2m, a metre taller than the average male African elephant.[2]
The smallest elephants, about the size of a calf or a large pig, were a
prehistoric variant that lived on the island of Crete until 5000 BC, possibly
3000 BC.
Elephants are increasingly
threatened by human intrusion. Between 1970 and 1989, the African elephant
population plunged from 1.3 million to about 600,000 in 1989; the current
population is estimated to be between 400,000 and 660,000.[3] The
elephant is now a protected species worldwide, placing restrictions on capture,
domestic use, and trade in products such as ivory.
Zoology
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. 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 is also
a potential danger in that if the forest elephant is not 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 at Chester Zoo, 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. 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 are said to have been
deformed and did not survive.
Comparative
view of the human and elephant frames, c1860.
African Elephant
The mammals of the genus Loxodonta,
often known collectively as African elephants, are currently found in 37
countries in sub-Saharan Africa.
African elephants are
distinguished from Asian elephants 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.
African elephants have
traditionally been classified as a single species composed of two distinct
subspecies, namely the savanna elephant (Loxodonta africana africana)
and the forest elephant (Loxodonta africana cyclotis), but recent DNA
analysis suggests that these may actually constitute distinct species.[4]
While this split is not universally accepted by experts[5] a third
species of African elephant has also been proposed.[6]
Under the two species
classification, 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 up to 13 ft (4 m) at the shoulder and weighing
approximately 15,400 lb (7,000 kg). The average male stands about 3 m (10 ft)
high at the shoulder and weighs about 5500–6000 kg, female being much smaller.
Most often, Savanna Elephants are found in open grasslands, marshes, and
lakeshores. They range over much of the savanna zone south of the Sahara.
The other postulated
species is the Forest Elephant (Loxodonta cyclotis). Compared with the
Savanna Elephant, its ears are usually smaller and rounder, and its tusks are
also thinner and straighter and are not directed outwards so much. The Forest
Elephant can weigh up to 10,000 lb (4,500 kg) and stand about 10 ft (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 African rain forests of central and western
Africa, though occasionally they do inhabit the edges of forests and overlap
territories and hybridize with bush elephants.
In 1979, Iain
Douglas-Hamilton estimated the continental population of African elephants at
around 1.3 million animals.[7] Although the estimate was
controversial due to the large dose of guesswork it contained,[8] it
is very widely cited and has become a de facto baseline that continues
to be incorrectly used to quantify downward population trends in the species.
Through the 1980s, Loxodonta received worldwide attention due to the
dwindling numbers of major populations in East Africa, largely as a result of
poaching. Today, according to IUCN’s African Elephant Status Report 2002[9]
there are approximately between 400,000 and 650,000 African elephants in the
wild. Although this estimate only covers approximately half of the total
elephant range, experts do not believe the true figure to be much higher, as it
is unlikely that large populations remain to be discovered.[10] By
far the largest populations are now found in Southern and Eastern Africa, which
together account for the majority of the continental population. According to a
recent analysis by IUCN experts, most major populations in Eastern and Southern
Africa are stable or have been steadily increasing since the mid-1990s, at an
average rate of 4.5% per annum.[11]
Elephant populations in
West Africa, on the other hand, are generally small and fragmented, and only
account for a small proportion of the continental total.[12] Much
uncertainty remains as to the size of the elephant population in Central
Africa, where the prevalence of forest makes population surveys logistically
difficult, but poaching for ivory and bushmeat is believed to be intense
through much of the region[13]
Asian Elephant
Today
scientists estimate the world population of Asian elephants, also called Indian
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.
Elephant In
Sri Lanka
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 Elephant (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 only an estimated 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 lb 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 in protecting the Sri Lankan Elephant from extinction.
Another subspecies, the
Indian 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 lb but are as tall as the Sri Lankan.
The mainland Asian can be found in 11 Asian countries, from India to Indonesia.
They prefer forested areas and transitional zones, between forests and
grasslands, where greater food variety is available.
The smallest of all the
elephants is the Sumatran Elephant (Elephas maximus sumatranus).
Population estimates for this group range from 2,100 to 3,000 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 1.7-2.6m at
the shoulder and weigh less than 3,000 kg (6,600 lb). 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.
In 2003 a further
subspecies was identified on Borneo. Named the Borneo pygmy elephant, it is
smaller and tamer than other Asian elephants. It also has relatively larger
ears, longer tail and straighter tusks.
Wikipedia
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