Elephant

From Wikipedia, the free encyclopedia

Jump to navigationJump to search
This article is about the living species. For extinct relatives also known as elephants,
see Elephantidae. For other uses, see Elephant (disambiguation).

Elephants

Temporal range: Pliocene–Present 

PreꞒ

Pg

From top left to right: the African

bush elephant, the Asian

 elephant and African forest elephant.

Scientific classification

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Proboscidea

Family: Elephantidae

Subfamily: Elephantinae

Groups included

 Loxodonta Anonymous,

1827

 Elephas Linnaeus, 1758

 †Palaeoloxodon Matsu

moto, 1925

Cladistically included but

traditionally excluded taxa

 †Mammuthus Brookes,

1828

 †Primelephas Maglio,

1970

Elephants are the largest existing land animals. Three species are currently

recognised: the African bush elephant, the African forest elephant, and the Asian
elephant. Elephantidae is the only surviving family of the order Proboscidea; extinct
members include the mastodons. The family Elephantidae also contains several extinct
groups, including the mammoths and straight-tusked elephants. African elephants have
larger ears and concave backs, whereas Asian elephants have smaller ears, and
convex or level backs. Distinctive features of all elephants include a
long proboscis called a trunk, tusks, large ear flaps, massive legs, and tough but
 sensitive skin. The trunk is used for breathing, bringing food and water to the mouth,
and grasping objects. Tusks, which are derived from the incisor teeth, serve both as
weapons and as tools for moving objects and digging. The large ear flaps assist in
maintaining a constant body temperature as well as in communication. The pillar-like
legs carry their great weight.
Elephants are scattered throughout sub-Saharan Africa, South Asia, and Southeast
Asia and are found in different habitats, including savannahs, forests, deserts,
and marshes. They are herbivorous, and they stay near water when it is accessible.
They are considered to be keystone species, due to their impact on their environments.
Elephants have a fission–fusion society, in which multiple family groups come together
to socialise. Females (cows) tend to live in family groups, which can consist of one
female with her calves or several related females with offspring. The groups, which do
not include bulls, are usually led by the oldest cow, known as the matriarch.
Males (bulls) leave their family groups when they reach puberty and may live alone or
with other males. Adult bulls mostly interact with family groups when looking for a mate.
They enter a state of increased testosterone and aggression known as musth, which
helps them gain dominance over other males as well as reproductive success. Calves
are the centre of attention in their family groups and rely on their mothers for as long as
three years. Elephants can live up to 70 years in the wild. They communicate by touch,
sight, smell, and sound; elephants use infrasound, and seismic communication over
long distances. Elephant intelligence has been compared with that
of primates and cetaceans. They appear to have self-awareness, and appear to
show empathy for dying and dead family members.
African bush elephants and Asian elephants are listed as endangered and African forest
elephants as critically endangered by the International Union for Conservation of
Nature (IUCN). One of the biggest threats to elephant populations is the ivory trade, as
the animals are poached for their ivory tusks. Other threats to wild elephants
include habitat destruction and conflicts with local people. Elephants are used
as working animals in Asia. In the past, they were used in war; today, they are often
controversially put on display in zoos, or exploited for entertainment in circuses.
Elephants are highly recognisable and have been featured in art, folklore, religion,
literature, and popular culture.

Contents

 1Etymology
 2Taxonomy and phylogeny
o 2.1Evolution and extinct relatives
 3Anatomy and morphology
o 3.1Size
o 3.2Bones
o 3.3Head
o 3.4Ears
o 3.5Trunk
o 3.6Teeth
 3.6.1Tusks
 o 3.7Skin
o 3.8Legs, locomotion, and posture
o 3.9Organs
o 3.10Body temperature
 4Behaviour and life history
o 4.1Ecology and activities
o 4.2Social organisation
o 4.3Sexual behaviour
 4.3.1Musth
 4.3.2Mating
o 4.4Birth and development
o 4.5Communication
o 4.6Intelligence and cognition
 5Conservation
o 5.1Status
o 5.2Threats
 6Association with humans
o 6.1Working animal
o 6.2Warfare
o 6.3Zoos and circuses
o 6.4Attacks
o 6.5Cultural depictions
 7See also
 8References
o 8.1Bibliography
 9Further reading
 10External links

Etymology
The word "elephant" is based on the Latin elephas (genitive elephantis) ("elephant"),
which is the Latinised form of the Greek ἐλέφας (elephas) (genitive ἐλέφαντος
(elephantos ), probably from a non-Indo-European language, likely Phoenician.  It is
[1] [2]

attested in Mycenaean Greek as e-re-pa (genitive e-re-pa-to) in Linear B syllabic script.

[3]

 As in Mycenaean Greek, Homer used the Greek word to mean ivory, but after the time
[4]

of Herodotus, it also referred to the animal.  The word "elephant" appears in Middle
[1]

English as olyfaunt (c.1300) and was borrowed from Old French oliphant (12th century).

[2]

Taxonomy and phylogeny

Afrotheria AfroinsectipTubulident
  hilia ata
   
Afroinsecti Macrosce
vora lidea
   
Afrosoric  
ida  
   
 
Paenungulat Hyracoi
a dea
   
Tethythe Probosci
ria dea
   
Sirenia  
   
 
 
A cladogram of the elephants within Afrotheria based on molecular
evidence[5]

Proboscidea  
   

early proboscideans, e.g. Moeritherium 

   
   

Deinotheriidae 

Elephantif  
ormes  
 

Mammutidae 

   
   

Gomphotheriidae 

   
    Stegodontidae 

Elephan  
tidae   Loxodonta 
 

   
    Mammuthus

 
  Elephas 

Proboscidea phylogeny based on upper molars.[6]

Elephantimorpha Elepha      
  ntidae      
   
 
 
 
     
     
 
 
 
 
 
 
 Phylogeny of modern elephants and close extinct relatives based on
molecular evidence[7]

See also: List of elephant species

Elephants belong to the family Elephantidae, the sole remaining family within the
order Proboscidea which belongs to the superorder Afrotheria. Their
closest extant relatives are the sirenians (dugongs and manatees) and the hyraxes, with
which they share the clade Paenungulata within the superorder Afrotheria.  Elephants [8]

and sirenians are further grouped in the clade Tethytheria. [9]

Three species of elephants are recognised; the African bush

elephant (Loxodonta africana) and forest elephant (Loxodonta cyclotis) of sub-Saharan
Africa, and the Asian elephant (Elephas maximus) of South and Southeast Asia.
 African elephants have larger ears, a concave back, more wrinkled skin, a sloping
[10]

abdomen, and two finger-like extensions at the tip of the trunk. Asian elephants have
smaller ears, a convex or level back, smoother skin, a horizontal abdomen that
occasionally sags in the middle and one extension at the tip of the trunk. The looped
ridges on the molars are narrower in the Asian elephant while those of the African are
more diamond-shaped. The Asian elephant also has dorsal bumps on its head and
some patches of depigmentation on its skin. [11]

Among African elephants, forest elephants have smaller and more rounded ears and
thinner and straighter tusks than bush elephants and are limited in range to the forested
areas of western and Central Africa.  Both were traditionally considered a single [12]

species, Loxodonta africana, but molecular studies have affirmed their status as

separate species.  In 2017, DNA sequence analysis showed that L. cyclotis is more
[13][14][15]

closely related to the extinct Palaeoloxodon antiquus, than it is to L. africana, possibly

undermining the genus Loxodonta as a whole. [16]

Evolution and extinct relatives

Over 180 extinct members and three major evolutionary radiations of the order
Proboscidea have been recorded.  The earliest proboscids, the [17]

African Eritherium and Phosphatherium of the late Paleocene, heralded the first

radiation.  The Eocene included Numidotherium, Moeritherium, and Barytherium from
[18]

Africa. These animals were relatively small and aquatic. Later on, genera such
as Phiomia and Palaeomastodon arose; the latter likely inhabited forests and open
woodlands. Proboscidean diversity declined during the Oligocene.  One notable [19]

species of this epoch was Eritreum melakeghebrekristosi of the Horn of Africa, which

may have been an ancestor to several later species.  The beginning of [20]

the Miocene saw the second diversification, with the appearance of the deinotheres and

the mammutids. The former were related to Barytherium and lived in Africa and Eurasia,
 while the latter may have descended from Eritreum  and spread to North America.
[21] [20] [21]

The second radiation was represented by the emergence of the gomphotheres in the

Miocene,  which likely evolved from Eritreum  and originated in Africa, spreading to
[21] [20]

every continent except Australia and Antarctica. Members of this group

included Gomphotherium and Platybelodon.  The third radiation started in the late [21]

Miocene and led to the arrival of the elephantids, which descended from, and slowly
replaced, the gomphotheres.  The African Primelephas gomphotheroides gave rise
[22]
to Loxodonta, Mammuthus, and Elephas. Loxodonta branched off earliest around the
Miocene and Pliocene boundary while Mammuthus and Elephas diverged later during
the early Pliocene. Loxodonta remained in Africa
while Mammuthus and Elephas spread to Eurasia, and the former reached North
America. At the same time, the stegodontids, another proboscidean group descended
from gomphotheres, spread throughout Asia, including the Indian subcontinent, China,
southeast Asia, and Japan. Mammutids continued to evolve into new species, such as
the American mastodon. [23]

At the beginning of the Pleistocene, elephantids experienced a high rate of speciation.

 The Pleistocene also saw the arrival of Palaeoloxodon namadicus, the largest
[24]

terrestrial mammal of all time.  Loxodonta atlantica became the most common species
[25]

in northern and southern Africa but was replaced by Elephas iolensis later in the
Pleistocene. Only when Elephas disappeared from Africa did Loxodonta become
dominant once again, this time in the form of the modern species. Elephas diversified
into new species in Asia, such as E. hysudricus and E. platycephus;  the latter the
[26]

likely ancestor of the modern Asian elephant.  Mammuthus evolved into several

[24]

species, including the well-known woolly mammoth.  Interbreeding appears to have

[26]

been common among elephantid species, which in some cases led to species with
three ancestral genetic components, such as the Palaeoloxodon antiquus.  In the Late [7]

Pleistocene, most proboscidean species vanished during the Quaternary

glaciation which killed off 50% of genera weighing over 5 kg (11 lb) worldwide. [27]

Proboscideans experienced several evolutionary trends, such as an increase in size,

which led to many giant species that stood up to 500 cm (16 ft 5 in) tall.  As with [25]

other megaherbivores, including the extinct sauropod dinosaurs, the large size of

elephants likely developed to allow them to survive on vegetation with low nutritional
value.  Their limbs grew longer and the feet shorter and broader.  The feet were
[28] [6]

originally plantigrade and developed into a digitigrade stance with cushion pads and

the sesamoid bone providing support.  Early proboscideans developed
[29]

longer mandibles and smaller craniums while more derived ones developed shorter

mandibles, which shifted the head's centre of gravity. The skull grew larger, especially
the cranium, while the neck shortened to provide better support for the skull. The
increase in size led to the development and elongation of the mobile trunk to provide
reach. The number of premolars, incisors and canines decreased. [6]

The cheek teeth (molars and premolars) of proboscideans became larger and more
specialized, especially after elephants started to switch from C3-plants to C4-grasses,
which caused their teeth to undergo a three-fold increase in teeth height as well as
substantial multiplication of lamellae after about five million years ago. Only in the last
million years or so did they return to a diet mainly consisting of C3 trees and shrubs. [30]

 The upper second incisors grew into tusks, which varied in shape from straight, to
[31]

curved (either upward or downward), to spiralled, depending on the species. Some

proboscideans developed tusks from their lower incisors.  Elephants retain certain
[6]

features from their aquatic ancestry, such as their middle ear anatomy. [32]

Several species of proboscideans lived on islands and experienced insular dwarfism.

This occurred primarily during the Pleistocene when some elephant populations
became isolated by fluctuating sea levels, although dwarf elephants did exist earlier in
the Pliocene. These elephants likely grew smaller on islands due to a lack of large or
viable predator populations and limited resources. By contrast, small mammals such as
rodents develop gigantism in these conditions. Dwarf elephants are known to have lived
in Indonesia, the Channel Islands of California, and several islands of
the Mediterranean.[33]