African elephant


African elephants are members of the genus Loxodonta comprising two living elephant species, the African bush elephant and the smaller African forest elephant. Both are social herbivores with grey skin. However, they differ in the size and colour of their tusks as well as the shape and size of their ears and skulls.
Both species are at a pertinent risk of extinction according to the IUCN Red List; as of 2021, the bush elephant is considered endangered while the forest elephant is considered critically endangered. They are threatened by habitat loss and fragmentation, along with poaching for the illegal ivory trade in several range countries.
Loxodonta is one of two extant genera in the family Elephantidae. The name refers to the lozenge-shaped enamel of their molar teeth. Fossil remains of Loxodonta species have been found in Africa, spanning from the Late Miocene onwards.

Etymology

The name Loxodonta comes from the Ancient Greek words λοξός and ὀδούς, referring to the lozenge-shaped enamel of the molar teeth, which differs significantly from the rounded shape of the Asian elephant's molar enamel.
Taxonomy and evolution
The first scientific description of the African elephant was written in 1797 by Johann Friedrich Blumenbach, who proposed the scientific name Elephas africanus.
Loxodonte was proposed as a generic name for the African elephant by Frédéric Cuvier in 1825.
An anonymous author used the Latinized spelling Loxodonta in 1827. This author was recognized as authority by the International Code of Zoological Nomenclature in 1999.
Elephas ''cyclotis'' was proposed by Paul Matschie in 1900, who described three African elephant zoological specimens from Cameroon whose skulls differed in shape from those of elephant skulls collected elsewhere in Africa. In 1936, Glover Morrill Allen considered this elephant to be a distinct species and called it the 'forest elephant'; later authors considered it to be a subspecies. Morphological and genetic analyses have since provided evidence for species-level differences between the African bush elephant and the African forest elephant.
In 1907, Richard Lydekker proposed six African elephant subspecies based on the different sizes and shapes of their ears. They are all considered synonymous with the African bush elephant.
A third species, the West African elephant, has also been proposed but needs confirmation. It is thought that this lineage has been isolated from the others for 2.4 million years.

Extinct African elephants

Between the late 18th and 21st centuries, the following extinct African elephants were described on the basis of fossil remains:
Relationships of living and extinct elephants based on DNA, after Palkopoulou et al. 2018.
The oldest species of Loxodonta known is Loxodonta cookei, with remains of the species known from around 7–5 million years ago, from remains found in Chad, Kenya, Uganda, and South Africa.
Analysis of nuclear DNA sequences indicates that the genetic divergence between African bush and forest elephants dates 2.6 – 5.6 million years ago. The African forest elephant was found to have a high degree of genetic diversity, likely reflecting periodic fragmentation of their habitat during the changes in the Pleistocene.
Gene flow between the two African elephant species was examined at 21 locations. The analysis revealed that several African bush elephants carried mitochondrial DNA of African forest elephants, indicating they hybridised in the savanna-forest transition zone in ancient times. However, despite the hybridisation at the contact zone between the two species, there appears to have been little effective gene flow between the two species since their initial split.
File:Palaeoloxodon_phylogeny.svg|thumb|243x243px|Phylogeny showing the placement of straight-tusked elephant in relation to other elephantids based on nuclear genomes, after Palkopoulou et al. 2018, showing introgression from African forest elephants
DNA from the European straight-tusked elephant indicates that the extinct elephant genus Palaeoloxodon is more closely related to African elephants than to Asian elephants or mammoths. Analysis of the genome of P. antiquus also shows that Palaeloxodon extensively hybridised with African forest elephants, with the mitochondrial genome and over 30% of the nuclear genome of P. antiquus deriving from L. cyclotis. This ancestry is closer to modern west African populations than to central African populations of forest elephants. Analysis of Chinese Palaeoloxodon mitogenomes suggests that this forest elephant ancestry was widely shared among Palaeoloxodon species.

Description

Skin, ears, and trunk

African elephants have grey folded skin up to thick that is covered with sparse, bristled dark-brown to black hair. Short tactile hair grows on the trunk, which has two finger-like processes at the tip, whereas Asian elephants only have one. Their large ears help to reduce body heat. Flapping them creates air currents and exposes the ears' inner sides where large blood vessels increase heat loss during hot weather. The trunk is a prehensile elongation of its upper lip and nose. This highly sensitive organ is innervated primarily by the trigeminal nerve, and is thought to be manipulated by about 40,000–60,000 muscles. Because of this muscular structure, the trunk is so strong that elephants can use it to lift about 3% of their own body weight. They use it for smelling, touching, feeding, drinking, dusting, producing sounds, loading, defending and attacking. Elephants sometimes swim underwater and use their trunks as snorkels.

Tusks and molars

Both male and female African elephants have tusks that grow from deciduous teeth called tushes, which are replaced by tusks when calves are about one year old. Tusks are composed of dentin, which forms small diamond-shaped structures in the tusk's center that become larger at its periphery. Tusks are primarily used to dig for roots and strip the bark from trees for food, for fighting each other during the mating season, and for defending themselves against predators. The tusks weigh from and can be from long. They are curved forward and continue to grow throughout the elephant's lifetime.
The dental formula of elephants is. Elephants have four molars; each weighs about and measures about long. As the front pair wears down and drops out in pieces, the back pair moves forward, and two new molars emerge in the back of the mouth. Elephants replace their teeth four to six times in their lifetimes. At around 40 to 60 years of age, the elephant loses the last of its molars and will likely die of starvation which is a common cause of death. African elephants have 24 teeth in total, six on each quadrant of the jaw. The enamel plates of the molars are fewer in number than in Asian elephants. The enamel of the molar teeth wears into a distinctive lozenge/loxodont shape characteristic to all members of the genus Loxodonta.'''' While some extinct species of Loxodonta retained permanent premolar teeth, these have been lost in both living species.

Size

The African bush elephant is the largest terrestrial animal. Under optimal conditions where individuals are capable of reaching full growth potential, mature fully grown females are tall at the shoulder and weigh, while mature fully grown bulls are tall and weigh on average. The largest recorded bull stood at the shoulder and is estimated to have weighed.
Its back is concave-shaped, while the back of the African forest elephant is nearly straight. The African forest elephant is considerably smaller. Fully grown African forest elephant males in optimal conditions where individuals are capable of reaching full growth potential are estimated to be on average tall and in weight.

Distribution and habitat

African elephants are distributed in Sub-Saharan Africa, where they inhabit Sahelian scrubland and arid regions, tropical rainforests, mopane and miombo woodlands. African forest elephant populations occur only in Central and West Africa.

Behavior and ecology

Sleeping pattern

Elephants are the animals with the lowest sleep times, especially African elephants. Research has found their average sleep to be only 2 hours in 24-hour cycles.

Family

Both African elephant species live in family units comprising several adult cows, their daughters and their subadult sons. Each family unit is led by an older cow known as the matriarch. African forest elephant groups are less cohesive than African bush elephant groups, probably due to the lack of natural predators.
When separate family units bond, they form kinship or bond groups. After puberty, male elephants tend to form close alliances with other males. While females are the most active members of African elephant groups, both male and female elephants are capable of distinguishing between hundreds of different low-frequency infrasonic calls to communicate with and identify each other.
Elephants use some vocalisations that are beyond the hearing range of humans, to communicate across large distances. Elephant mating rituals include the gentle entwining of trunks.
Bulls were believed to be solitary animals, becoming independent once reaching maturity. New research suggests that bulls maintain ecological knowledge for the herd, facilitating survival when searching for food and water, which also benefits the young bulls who associate with them. Bulls only return to the herd to breed or to socialize; they do not provide parental care to their offspring or raise them, but rather play a fatherly role in general to younger bulls to show dominance.