The African bush elephant
The African bush elephant (Loxodonta africana), also known as the African savanna elephant, is the largest living terrestrial animal, with bulls reaching a shoulder height of up to 3.96 m (13.0 ft) and a body mass of up to 10.4 t (11.5 short tons).
It is distributed across 37 African countries and inhabits forests, grasslands and woodlands, wetlands and agricultural land. Since 2004, it has been listed as Vulnerable on the IUCN Red List.
It is threatened foremost by habitat destruction, and in parts of its range also by poaching for meat and ivory. It is a social mammal, traveling in herds composed of cows and their offspring.
Adult bulls usually live alone or in small bachelor groups. It is a herbivore, feeding on grasses, creepers, herbs, leaves and bark.
Taxonomy
Elephas africanus was the scientific name proposed by Johann Friedrich Blumenbach in 1797. Loxodonte was proposed as generic name for African elephants by Georges Cuvier in 1825. This name refers to the lozenge-shaped enamel of the molar teeth, which differs significantly from the shape of the Asian elephant’s molar enamel.
In the 19th and 20th centuries, several zoological specimens were described by naturalists and curators of natural history museums from various parts of Africa, including:
- Elephas (Loxodonta) oxyotis and Elephas (Loxodonta) knochenhaueri by Paul Matschie in 1900. The first was a specimen from the upper Atbara River in northern Ethiopia, and the second a specimen from the Kilwa area in Tanzania.
- Elephas africanus toxotis, selousi, peeli, cavendishi, orleansi and rothschildi by Richard Lydekker in 1907 who assumed that ear size is a distinguishing character for a race. These specimens were shot in South Africa, Mashonaland in Zimbabwe, Aberdare Mountains and Lake Turkana area in Kenya, in Somaliland and in western Sudan, respectively.
- North African elephant (L. a. pharaohensis) by Paulus Edward Pieris Deraniyagala in 1948 was a specimen from Fayum in Egypt.
Today, these names are all considered synonyms.
Phylogeny
A genetic study based on mitogenomic analysis revealed that the African and Asian elephant genetically diverged about 7.6 million years ago.
Phylogenetic analysis of nuclear DNA of bush and forest elephants, Asian elephant, woolly mammoth and American mastodon revealed that the bush elephant and the African forest elephant form a sister group that genetically diverged at least 1.9 million years ago.
They are therefore considered distinct species. Gene flow between the two species however, might have occurred after the split.
Characteristics
Size
They are the largest and heaviest land animal on Earth, with a maximum recorded shoulder height of an adult bull of 3.96 m (13.0 ft) and an estimated weight of up to 10.4 t (11.5 short tons).
On average, males are about 3.20 m (10.5 ft) tall at the shoulder and weigh 6.0 t (6.6 short tons), while females are much smaller at about 2.60 m (8.53 ft) tall at the shoulder and 3.0 t (3.3 short tons) in weight.
Elephants attain their maximum stature when they complete the fusion of long-bone epiphyses, occurring in males around the age of 40 and females around the age of 25.
Skin and ears
The bush elephant has grey skin with scanty hairs. Its large ears cover the whole shoulder, and can grow as large as 2 m × 1.5 m (6.6 ft × 4.9 ft).
Large ears help to reduce body heat; flapping them creates air currents and exposes large blood vessels on the inner sides to increase heat loss during hot weather.
There ears are pointed and triangular shaped. Its occipital plane slopes forward. Its back is shaped markedly concave. Its sturdy tusks are curved out and point forward.
Trunk
The trunk is a prehensile elongation of the upper lip and nose. Short tactile hair grows on the trunk, which has two finger-like processes on the tip.
This highly sensitive organ is innervated primarily by the trigeminal nerve, and 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 for lifting about 3% of their own body weight.
They use it for smelling, touching, feeding, drinking, dusting, sound production, loading, defending and attacking. Functional loss of the trunk due to floppy trunk syndrome sometimes forces elephants to carry their trunks over their tusks and walk into deep water in order to drink.
Tusks
Both sexes have tusks, which erupt when they are 1–3 years old and grow throughout life. Tusks grow from deciduous teeth known as tushes that develop in the upper jaw and consist of a crown, root and pulpal cavity, which are completely formed soon after birth.
Tushes reach a length of 5 cm (2 in). The tusks erupt when elephants are 1–3 years old and grow throughout life. They are composed of dentin and coated with a thin layer of cementum.
Their tips bear a conical layer of enamel that is usually worn off when the elephant is five years old. Tusks of bulls grow faster than tusks of females.
Mean weight of tusks at the age of 60 years is 109 kg (240 lb) in bulls, and 17.7 kg (39.0 lb) in cows. The longest known tusk of an African bush elephant measured 3.51 m (11.5 ft) and weighed 117 kg (258 lb).
Molars
The dental formula of them is 1.0.3.30.0.3.3 × 2 = 26. It develops six molars in each jaw quadrant that erupt at different ages and differ in size.
The first molars grow to a size of 2 cm (0.79 in) wide by 4 cm (1.6 in) long, are worn by the age of one year and lost by the age of about 2.5 years.
The second molars start protruding at the age of about six months, grow to a size of 4 cm (1.6 in) wide by 7 cm (2.8 in) long and are lost by the age of 6–7 years.
The third molars protrude at the age of about one year, grow to a size of 5.2 cm (2.0 in) wide by 14 cm (5.5 in) long and are lost by the age of 8–10 years.
The fourth molars show by the age of 6–7 years, grow to a size of 6.8 cm (2.7 in) wide by 17.5 cm (6.9 in) long and are lost by the age of 22–23 years.
The dental alveoli of the fifth molars are visible by the age of 10–11 years. They grow to a size of 8.5 cm (3.3 in) wide by 22 cm (8.7 in) long and are worn by the age of 45–48 years.
The dental alveoli of the last molars are visible by the age of 26–28 years. They grow to a size of 9.4 cm (3.7 in) wide by 31 cm (1.0 ft) long and are well worn by the age of 65 years.
Distribution and habitat
The bush elephant occurs in Sub-Saharan Africa including Uganda, Kenya, Tanzania, Botswana, Zimbabwe, Namibia, Zambia, and Angola.
It moves between a variety of habitats, including subtropical and temperate forests, dry and seasonally flooded grasslands and woodlands, wetlands and agricultural land from sea level to mountain slopes. In Mali and Namibia, it also inhabits desert areas.
In Ethiopia, they has historically been recorded up to an altitude of 2,500 m (8,200 ft). By the late 1970s, the population had declined to a herd in the Dawa River valley and one close to the Kenyan border.
Predators
In Botswana’s Chobe National Park, subadult elephants are preyed upon by lions.
They attacked and fed on elephants when smaller prey species were scarce. Between 1993 and 1996, lions successfully attacked 74 elephants; 26 were older than nine, and one was a bull of over 15 years.
Most were killed at night, and hunts occurred more often during waning moon nights than during bright moon nights. In the same park, lions killed eight elephants in October 2005 that were aged between one and 11 years, two of them older than eight years.
Successful hunts took place after dark when prides exceeded 27 lions and herds were smaller than five elephants.
Status
In 1996, IUCN Red List assessors for they considered the species Endangered. Since 2004, it has been assessed Vulnerable, as the global population was estimated to be increasing at a rate of 4% per year. About 70% of its range is located outside protected areas.
In 2016, the global population was estimated at 415,428 ± 20,111 individuals distributed in a total area of 20,731,202 km2 (8,004,362 sq mi), of which 30% is protected.
42% of the total population lives in nine Southern African countries comprising 293,447 ± 16,682 individuals; Africa’s largest population lives in Botswana with 131,626 ± 12,508 individuals.
In captivity
The social behavior of elephants in captivity mimics that of those in the wild. Females are kept with other females, in groups, while males tend to be separated from their mothers at a young age, and are kept apart.
According to Schulte, in the 1990s, in North America, a few facilities allowed male interaction. Elsewhere, males were only allowed to smell each other. Males and females were allowed to interact for specific purposes such as breeding.
In that event, females were more often moved to the male than the male to the female. Females are more often kept in captivity because they are easier and less expensive to house.