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ELEPHANT,
largest living land mammal, and the only remaining representative
of the order Proboscidae, which during the Pleistocene period roamed
every landmass except Australia and Antarctica. Two extant species,
the Indian elephant, Elephas maximus, of India
and Southeast Asia, and the African elephant, Loxodonta
africana, ranging south of the Sahara, are now limited
to tropical forests, savannas, and river valleys. The Indian elephant
reaches heights of 3 m (10 ft), and the African elephant, 4 m (13
ft). Earlier proboscideans—the mammoths, with some reaching
4.5 m (15 ft), and the smaller mastodons as well—survived
up to the time of the Paleolithic humans, whose cave drawings depicted
woolly mammoths.
The boneless, muscular trunk, the most distinctive feature
of proboscideans, is actually a greatly elongated upper lip and
nose used to convey grasses, leaves, and water to the mouth. Present-day
elephants consume as much as 225 kg (495 lb) of forage a day in
this manner and drink as much as 190 liters (50 gal) of water, drawing
it through their nostrils and squirting it into the mouth. An extremely versatile
organ, the trunk is also used to trumpet calls, pull down trees,
rip off foliage, and draw up dust for dust bathing. It is also a
highly sensitive organ, which the animals raise into the air to
detect the faintest wind-borne scents. By means of fingerlike lobes
on the end of the trunk and by the sucking action of the two nostrils,
elephants can pick up and examine small objects.
The tusks, which are deeply embedded in the skull, are actually enormously
enlarged incisors. Record tusks of the male African elephant have
measured 3.5 m (10.5 ft) long. Elephants have only four molar or
grinding teeth, one to each side of the upper and lower jaws; each
is a massive plate about 30 cm (about 12 in) long and 10 cm (4 in)
wide. When worn down by the coarse vegetation elephants eat, these
teeth are replaced by larger ones that shift forward from the rear
of the jaws. At about 40 years of age, the animal’s final
and largest molars come into position and last for about 20 years. Elephants
have the same longevity as humans.
In addition to its greater size, L. africana can
be quickly distinguished from E. maximus by its
larger ears, which may reach a length of 1.5 m (about 5 ft) from
top to bottom. The African elephant is tallest at the shoulder,
has more wrinkled skin, and bears tusks in both male and female.
The Indian elephant is tallest at the arch of the back, bears tusks
in the male only, and has one lobe instead of two on its trunk.
Despite their great weight, which in African elephants reaches 7000
kg (15,400 lb) and in Indian elephants reaches 5000 kg (11,000 lb),
elephants walk almost noiselessly and with exceptional grace, their
columnar legs keeping their bulk moving forward in smooth, rhythmic strides.
A thick cushion of resilient tissue grows on the base of the foot,
absorbing the shock of the weight and enabling the animal to walk
high on its hooflike toes. Elephants normally walk about 6.4 km/hr
(about 4 mph) and can charge at up to 40 km/hr (25 mph).
They cannot gallop or jump over ditches, but they readily take to rivers
and lakes where the water supports them and enables them to swim
for long distances without tiring.
The elephant’s hearing is poor, and the great ears
of the African elephant are probably used as much for ventilation
and making threatening gestures as for hearing. The eyesight is
equally poor, the eyes being comparatively small and fixed on the
animal’s large and relatively immobile head. The most sensitive
organ is the trunk, which is frequently at work, picking up scents
of food and danger from the ground and the air. Observers first
noted in the 1980s that elephants produce, with their nasal passages,
rumbling sounds below the range of human hearing. Because such sounds
travel well and because elephant hearing is better at low frequencies,
the animals very likely use these sounds to communicate with one
another.
Elephants are gregarious and keenly sensitive to one another’s
calls and movements. They associate in herds of 15 to 30 or more
usually related members led by an old female. Herds of Indian elephants
are usually made up of females, immature elephants, and one old
bull; those of African elephants also include mature bulls. Bulls
driven from herds live alone or in bachelor herds. Elephants commonly
feed in the morning, evening, and at night, and rest during the
middle of the day. When migrating, they often trek single file.
Cow elephants mate by their 18th year, usually with a bull
that is able to contend with other bulls in the herd. A mating pair
often separates from the herd for several weeks. After a gestation
period of 21 to 22 months, usually one calf is born and is able
to follow the herd within a few days. Calves are vunerable to leopards
and tigers, which are among the few predators of elephants. The
calves suckle the female’s teats, which are just behind
the forelegs, for nearly five years before weaning. Cows give birth
to from 5 to 12 calves in a lifetime.
Although African elephants can be trained, the Indian elephant
has by far the longer tradition of service to humans. Indian elephants
are still used for logging, especially in mountainous terrain, and
were probably employed as work animals as early as 2000 bc.
They were used in war in 326 bc against Alexander the Great;
and 37 elephants accompanied the Carthaginian general Hannibal and
his army across the Alps in 218 bc. Since elephants rarely
bear young in captivity, they are corralled in the wild, often with
the use of domestic elephants and mahouts (professional elephant
handlers). A captured calf is assigned a keeper, who remains with
it for life, training it when it reaches 14 years of age and putting
it to hard labor at 25 years.
The earliest ancestor of elephants was the moeritherium, a
pig-sized animal with a tapirlike snout, found in Upper Eocene deposits
(about 60 million years old). Present-day elephants can be traced
to two families in the Pleistocene period: the mastodons (Mastodontidae),
which became extinct; and the elephants (Elephantidae), which also
included the mammoths. Of the Elephantidae, only the African and
Indian species remain. They are of relatively recent origin, no
fossils of them having been found in the late Pliocene, about 12
to 2 million years ago.
African elephant populations have been severely reduced in
recent decades because of ivory hunting and the expansion of cattle-grazing
lands. Although herds are thriving in parks, their overbrowsing
is causing serious ecological damage that threatens many other African
species.