Elephants

This category contains all animals that are elephants or elephant-like creatures.

Elephants are the largest living land animals. Three living speciesare currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantidae and the order Proboscidea; extinct relatives include mammoths and mastodons. Distinctive features of elephants include a long proboscis called a trunk, tusks, large ear flaps, pillar-like legs, and tough but sensitive grey skin. The trunk is prehensile, 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. African elephants have larger ears and concave backs, whereas Asian elephants have smaller ears and convex or level backs.

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 leader of a female group, usually the oldest cow, is 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 possibly show concern for dying and dead individuals of their kind.

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 employed for entertainment in circuses. Elephants have an iconic status in human culture and have been featured in art, folklore, religion, literature, and popular culture.

Etymology[]

The word elephant is based on the Latin elephas (genitive elephantis) 'elephant', which is the Latinised form of the ancient Greek ἐλέφας (elephas) (genitive ἐλέφαντος (elephantos)), probably from a non-Indo-European language, likely Phoenician. It is attested in Mycenaean Greek as e-re-pa (genitive e-re-pa-to) in Linear B syllabic script. As in Mycenaean Greek, Homer used the Greek word to mean ivory, but after the time of Herodotus, it also referred to the animal. The word elephant appears in Middle English as olyfaunt(c. 1300) and was borrowed from Old French oliphant (12th century).

Taxonomy[]

Elephants belong to the family Elephantidae, the sole remaining family within the order Proboscidea. 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 and sirenians are further grouped in the clade Tethytheria.

Three species of living elephants are recognised; the African bush elephant (Loxodonta africana), forest elephant (Loxodonta cyclotis) and Asian elephant (Elephas maximus). African elephantswere traditionally considered a single species, Loxodonta africana, but molecular studies have affirmed their status as separate species.Mammoths (Mammuthus) are nested within living elephants as they are more closely related to Asian elephants than to African elephants. Another extinct genus of elephant, Palaeoloxodon, is also recognised, which appears to have close affinities with and to have hybridised with African elephants.

Evolution[]

Over 180 extinct members of order Proboscidea have been described. The earliest proboscideans, the African Eritherium and Phosphatherium are known from the late Paleocene. The Eocene included Numidotherium, Moeritherium and Barytherium from Africa. These animals were relatively small and, some, like Moeritherium and Barytherium were probably amphibious. Later on, genera such as Phiomia and Palaeomastodon arose; the latter likely inhabited more forested areas. Proboscidean diversification changed little during the Oligocene. One notable species of this epoch was Eritreum melakeghebrekristosi of the Horn of Africa, which may have been an ancestor to several later species.

A major event in proboscidean evolution was the collision of Afro-Arabia with Eurasia, during the Early Miocene, around 18–19 million years ago, allowing proboscideans to disperse from their African homeland across Eurasia and later, around 16–15 million years ago into North America across the Bering Land Bridge. Proboscidean groups prominent during the Miocene include the deinotheres, along with the more advanced elephantimorphs, including mammutids (mastodons), gomphotheres, amebelodontids (which includes the "shovel tuskers" like Platybelodon), choerolophodontidsand stegodontids. Around 10 million years ago, the earliest members of the family Elephantidae emerged in Africa, having originated from gomphotheres.

Elephantids are distinguished from earlier proboscideans by a major shift in the molar morphology to parallel lophs rather than the cusps of earlier proboscideans, allowing them to become higher-crowned (hypsodont) and more efficient in consuming grass. The Late Miocene saw major climactic changes, which resulted in the decline and extinction of many proboscidean groups. The earliest members of the modern genera of Elephantidae appeared during the latest Miocene–early Pliocene around 5 million years ago. The elephantid genera Elephas (which includes the living Asian elephant) and Mammuthus (mammoths) migrated out of Africa during the late Pliocene, around 3.6 to 3.2 million years ago.

Over the course of the Early Pleistocene, all non-elephantid probobscidean genera outside of the Americas became extinct with the exception of Stegodon, with gomphotheres dispersing into South America as part of the Great American interchange, and mammoths migrating into North America around 1.5 million years ago. At the end of the Early Pleistocene, around 800,000 years ago the elephantid genus Palaeoloxodondispersed outside of Africa, becoming widely distributed in Eurasia. Proboscideans underwent a dramatic decline during the Late Pleistocene, with all remaining non-elephantid proboscideans (including Stegodon, mastodons, and the gomphotheres Cuvieronius and Notiomastodon) and Palaeoloxodon becoming extinct, with mammoths only surviving in relict populations on islands around the Bering Strait into the Holocene, with their latest survival being on Wrangel Island around 4,000 years ago.

Over the course of their evolution, probobscideans grew in size. With that came longer limbs and wider feet with a more digitigrade stance, along with a larger head and shorter neck. The trunk evolved and grew longer to provide reach. The number of premolars, incisors, and canines decreased, and the cheek teeth (molars and premolars) became longer and more specialised. The incisors developed into tusks of different shapes and sizes. Several species of proboscideans became isolated on islands and experienced insular dwarfism, some dramatically reducing in body size, such as the 1 metre (3.3 ft) tall dwarf elephant species Palaeoloxodon falconeri.

Living species[]

Anatomy[]

link=https://en.wikipedia.org/wiki/File:Elephant_skeleton.jpg|thumb|African bush elephant skeleton Elephants are the largest living terrestrial animals. The skeleton is made up of 326–351 bones. The vertebrae are connected by tight joints, which limit the backbone's flexibility. African elephants have 21 pairs of ribs, while Asian elephants have 19 or 20 pairs. The skull contains air cavities (sinuses) that reduce the weight of the skull while maintaining overall strength. These cavities give the inside of the skull a honeycomb-like appearance. By contrast, the lower jaw is dense. The cranium is particularly large and provides enough room for the attachment of muscles to support the entire head. The skull is built to withstand great stress, particularly when fighting or using the tusks. The brain is surrounded by arches in the skull, which serve as protection. Because of the size of the head, the neck is relatively short to provide better support. Elephants are homeotherms and maintain their average body temperature at ~ 36 °C (97 °F), with a minimum of 35.2 °C (95.4 °F) during the cool season, and a maximum of 38.0 °C (100.4 °F) during the hot dry season.

Behaviour and ecology[]

An Asian elephant feeding on grass in Sri Lanka

https://upload.wikimedia.org/wikipedia/commons/thumb/1/17/African_elephant_%28Loxodonta_africana%29_reaching_up_1.jpg/194px-African_elephant_%28Loxodonta_africana%29_reaching_up_1.jpg

An African bush elephant using its prehensile trunk for foraging

Elephants are herbivorous and will eat leaves, twigs, fruit, bark, grass, and roots. African elephants mostly browse, while Asian elephants mainly graze. They can eat as much as 300 kg (660 lb) of food and drink 40 L (11 US gal) of water in a day. Elephants tend to stay near water sources. They have morning, afternoon, and nighttime feeding sessions. At midday, elephants rest under trees and may doze off while standing. Sleeping occurs at night while the animal is lying down. Elephants average 3–4 hours of sleep per day. Both males and family groups typically move no more than 20 km (12 mi) a day, but distances as far as 180 km (112 mi) have been recorded in the Etosha region of Namibia. Elephants go on seasonal migrations in response to changes in environmental conditions. In northern Botswana, they travel 325 km (202 mi) to the Chobe River after the local waterholes dry up in late August. link=https://en.wikipedia.org/wiki/File:Forest_elephant_group_2_(6987537761).jpg|thumb|Forest elephants digging for minerals to consume Because of their large size, elephants have a huge impact on their environments and are considered keystone species. Their habit of uprooting trees and undergrowth can transform savannah into grasslands; smaller herbivores can access trees mowed down by elephants. When they dig for water during droughts, they create waterholes that can be used by other animals. When they use waterholes, they end up making them bigger. At Mount Elgon, elephants dig through caves and pave the way for ungulates, hyraxes, bats, birds and insects. Elephants are important seed dispersers; African forest elephants consume and deposit many seeds over great distances, with either no effect or a positive effect on germination. In Asian forests, large seeds require giant herbivores like elephants and rhinoceros for transport and dispersal. This ecological niche cannot be filled by the smaller Malayan tapir. Because most of the food elephants eat goes undigested, their dung can provide food for other animals, such as dung beetles and monkeys. Elephants can have a negative impact on ecosystems. At Murchison Falls National Park in Uganda, elephant numbers have threatened several species of small birds that depend on woodlands. Their weight causes the soil to compress, leading to runoff and erosion.

Elephants typically coexist peacefully with other herbivores, which will usually stay out of their way. Some aggressive interactions between elephants and rhinoceros have been recorded. The size of adult elephants makes them nearly invulnerable to predators. Calves may be preyed on by lions, spotted hyenas, and wild dogs in Africa and tigers in Asia. The lions of Savuti, Botswana, have adapted to hunting elephants, mostly calves, juveniles or even sub-adults. There are rare reports of adult Asian elephants falling prey to tigers. Elephants tend to have high numbers of parasites, particularly nematodes, compared to many other mammals. This is due to them being largely immune to predators, which would otherwise kill off many of the individuals with significant parasite loads.

Social organisation[]

link=https://en.wikipedia.org/wiki/File:Serengeti_Elefantenherde1.jpg|thumb|A family of African bush elephants Elephants are generally gregarious animals. African bush elephants in particular have a complex, stratified social structure. Female elephants spend their entire lives in tight-knit matrilineal family groups. They are led by the matriarch, who is often the eldest female. She remains leader of the group until death or if she no longer has the energy for the role; a study on zoo elephants found that the death of the matriarch led to greater stress in the surviving elephants. When her tenure is over, the matriarch's eldest daughter takes her place instead of her sister (if present).One study found that younger matriarchs take potential threats less seriously. Large family groups may split if they cannot be supported by local resources.

At Amboseli National Park, Kenya, female groups may consist of around ten members, including four adults and their dependent offspring. Here, a cow's life involves interaction with those outside her group. Two separate families may associate and bond with each other, forming what are known as bond groups. During the dry season, elephant families may aggregate into clans. These may number around nine groups, in which clans do not form strong bonds but defend their dry-season ranges against other clans. The Amboseli elephant population is further divided into the "central" and "peripheral" subpopulations.

Female Asian elephants tend to have more fluid social associations. In Sri Lanka, there appear to be stable family units or "herds" and larger, looser "groups". They have been observed to have "nursing units" and "juvenile-care units". In southern India, elephant populations may contain family groups, bond groups and possibly clans. Family groups tend to be small, with only one or two adult females and their offspring. A group containing more than two cows and their offspring is known as a "joint family". Malay elephant populations have even smaller family units and do not reach levels above a bond group. Groups of African forest elephants typically consist of one cow with one to three offspring. These groups appear to interact with each other, especially at forest clearings. link=https://en.wikipedia.org/wiki/File:Asian_Elephant_at_Corbett_National_Park_15.jpg|thumb|Lone bull: Adult male elephants spend much of their time alone or in single-sex groups Adult males live separate lives. As he matures, a bull associates more with outside males or even other families. At Amboseli, young males may be away from their families 80% of the time by 14–15 years of age. When males permanently leave, they either live alone or with other males. The former is typical of bulls in dense forests. A dominance hierarchy exists among males, whether they are social or solitary. Dominance depends on age, size, and sexual condition.Male elephants can be quite sociable when not competing for mates and form vast and fluid social networks. Older bulls act as the leaders of these groups. The presence of older males appears to subdue the aggression and "deviant" behaviour of younger ones.The largest all-male groups can reach close to 150 individuals. Adult males and females come together to breed. Bulls will accompany family groups if a cow is in oestrous.

Communication[]

Main article: Elephant communication

https://upload.wikimedia.org/wikipedia/commons/thumb/c/cd/Three_elephant%27s_curly_kisses.jpg/200px-Three_elephant%27s_curly_kisses.jpg

Asian elephants greeting each other by inter-twining their trunks

Low frequency rumble visualised with acoustic camera

Elephants communicate in various ways. Individuals greet one another by touching each other on the mouth, temporal glands and genitals. This allows them to pick up chemical cues. Older elephants use trunk-slaps, kicks, and shoves to control younger ones. Touching is especially important for mother–calf communication. When moving, elephant mothers will touch their calves with their trunks or feet when side-by-side or with their tails if the calf is behind them. A calf will press against its mother's front legs to signal it wants to rest and will touch her breast or leg when it wants to suckle.

Visual displays mostly occur in agonistic situations. Elephants will try to appear more threatening by raising their heads and spreading their ears. They may add to the display by shaking their heads and snapping their ears, as well as tossing around dust and vegetation. They are usually bluffing when performing these actions. Excited elephants also raise their heads and spread their ears but additionally may raise their trunks. Submissive elephants will lower their heads and trunks, as well as flatten their ears against their necks, while those that are ready to fight will bend their ears in a V shape.

Elephants produce several vocalisations—some of which pass though the trunk—for both short and long range communication. This includes trumpeting, bellowing, roaring, growling, barking, snorting, and rumbling. Elephants can produce infrasonic rumbles. For Asian elephants, these calls have a frequency of 14–24 Hz, with sound pressure levels of 85–90 dB and last 10–15 seconds. For African elephants, calls range from 15 to 35 Hz with sound pressure levels as high as 117 dB, allowing communication for many kilometres, possibly over 10 km (6 mi). Elephants are known to communicate with seismics, vibrations produced by impacts on the earth's surface or acoustical waves that travel through it. An individual foot stomping or mock charging can create seismic signals that can be heard at travel distances of up to 32 km (20 mi). Seismic waveforms produced by rumbles travel 16 km (10 mi).

Intelligence and cognition[]

Main article: Elephant cognition Elephants are among the most intelligent animals. They exhibit mirror self-recognition, an indication of self-awareness and cognition that has also been demonstrated in some apes and dolphins. One study of a captive female Asian elephant suggested the animal was capable of learning and distinguishing between several visual and some acoustic discrimination pairs. This individual was even able to score a high accuracy rating when re-tested with the same visual pairs a year later. Elephants are among the species known to use tools. An Asian elephant has been observed fine-tuning branches for use as flyswatters. Tool modification by these animals is not as advanced as that of chimpanzees. Elephants are popularly thought of as having an excellent memory. This could have a factual basis; they possibly have cognitive maps which give them long lasting memories of their environment on a wide scale. Individuals may be able to remember where their family members are located.

Scientists debate the extent to which elephants feel emotion. They are attracted to the bones of their own kind, regardless of whether they are related. As with chimpanzees and dolphins, a dying or dead elephant may elicit attention and aid from others, including those from other groups. This has been interpreted as expressing "concern"; however, the Oxford Companion to Animal Behaviour (1987) said that "one is well advised to study the behaviour rather than attempting to get at any underlying emotion".