African bush elephant

The African bush elephant or African savanna elephant (Loxodonta africana) is the larger of the two species of African elephant. Both it and the African forest elephant have usually been classified as a single species, known simply as the African elephant, but recent evidence has seen the forest elephant classified as a distinct species. Some authorities still consider the currently available evidence as insufficient for splitting African elephants into two species.

Description
African bush elephants are the largest living terrestrial animals, being up to 3.96 m tall at the shoulders (a male shot in 1974), on average, males are 3.3 m tall at the shoulders and 5.5 tonnes in weight, while females are much smaller at 2.8 m tall and 3.7 tonnes in weight. The most characteristic features of African elephants are their very large ears, which they use to radiate excess heat, and their trunk, an extension of the upper lip and nose with two opposing extensions at its end, different from the Asian elephant, which only has one. The trunk is used for communication and handling objects and food. African elephants also have bigger tusks, large modified incisors that grow throughout an elephant's lifetime. They occur in both males and females and are used in fights and for marking, feeding, and digging.

Diet
The African bush elephant is herbivorous. Its diet varies according to its habitat; elephants living in forests, partial deserts, and grasslands all eat different proportions of herbs and tree or shrubbery leaves. Elephants inhabiting the shores of Lake Kariba have been recorded eating underwater plant life. To break down the plants it consumes, the African bush elephant has four large molars, two in each mandible of the jaw. Each of these molars is 10 cm wide and 30 cm long. Over time, these molars are worn away, and new ones are grown to replace them as the elephant ages. Around the age of 15, the milk teeth are replaced by new ones that last until the age of 30, and then by another set which wear off past the age of 40, being replaced by the last set of teeth that last until about the age of 65–70. Not much later, the animal dies of starvation from not being able to feed correctly. Specimens over 80 years old are known in captivity.

This species typically ingests an average of 225 kg of vegetable matter daily, which is defecated without being fully digested. That, combined with the long distances it can cover daily in search of more food, contributes notably to the dispersion of many plant seeds that germinate in the middle of a nutrient-filled feces mound. Elephants rip apart all kind of plants, and knock down trees with the tusks if they are not able to reach the tree leaves. Elephants also drink great quantities of water, over 190 l per day.

Social behavior
Herds are made up of related females and their young, directed by the eldest female, called the matriarch. Infrequently, an adult male goes with them, but those usually leave the herd when reaching adolescence to form bachelor herds with other elephants of the same age. Later, they lead a solitary life, approaching the female herds only during the mating season. Nevertheless, elephants do not get too far from their families and recognize them when re-encountered. Sometimes, several female herds can blend for a period of time, reaching even hundreds of individuals. The matriarch decides the route and has shown the other members of the herd all the water sources she knows, which the rest can memorize for the future. The relations among the members of the herd are very tight; when a female has given birth to a baby, the rest have acknowledged it by touching her with the trunk; when an old elephant has died, the rest of the herd have stayed by the corpse for a while. The famous elephant graveyards are false, but these animals have recognized a carcass of their species when they found one during their trips, and even if it was a stranger, they formed around it, and sometimes they even touched its forehead with their trunks.

Mating happens when the female becomes receptive, an event that can occur anytime during the year. When she is ready, she starts emitting infrasounds to attract the males, sometimes from kilometers away. The adult males start arriving at the herd during the following days and begin fighting, causing some injuries and even broken tusks. The female shows her acceptance of the victor by rubbing her body against his. They mate, and then both go their own way. After 22 months of gestation (the longest among mammals), the female gives birth to a single 90-cm-high calf which weighs more than 100 kg. The baby feeds on the mother's milk until the age of five, but also eats solid food from as early as six months old. Just a few days after birth, the calf can follow the herd by foot.

Like all species of elephant, the male African bush elephant experiences musth, a period of extreme aggression accompanied with high testosterone levels. A bull in musth has been known to attack anything which disturbs him including his family members, humans, and other passive animals such as giraffes and rhinoceros. In one case a young male African bush elephant has been witnessed killing a rhinoceros during musth.

Predators
The adult African bush elephant generally has no natural predators (other than humans) due to its great size, but the calves (especially the newborns) are vulnerable to lion and crocodile attacks, and (rarely) to leopard and hyena attacks. Some prides of lions prey on both infants and juveniles, especially in the drought months. Lions in Chobe National Park in Botswana have been observed for some time taking both infants (23% of elephant kills) and juveniles. Predation, as well as drought, contribute significantly to infant mortality.

Humans are the elephant's major predator. They have been hunted for meat, skin, bones, and tusks. Trophy hunting increased in the 19th and 20th centuries, when tourism and plantations increasingly attracted sport hunters. In 1989, hunting of the African bush elephant for ivory trading was forbidden, after the elephant population fell from several million at the beginning of the 20th century to fewer than 700,000. Trophy hunting continues today. The population of African bush elephants was halved during the 1980s. Scientists then estimated, if no protective measures were taken, the wild elephant would be extinct by 1995. The protection the elephant now receives has been partially successful, but despite increasingly severe penalties imposed by governments against illegal hunting, poaching is still common. CITES still considers this species as threatened with extinction.

Species differences
A 2010 genetic study confirmed the African bush elephant and the African forest elephant are distinct species. By sequencing DNA of 375 nuclear genes, scientists determined the two species diverged around the same time as the Asian elephant and the woolly mammoth, and are as distinct from one another as those two species. , conservation organizations, such as the United Nations Environment Programme's World Conservation Monitoring Centre and the International Union for Conservation of Nature (IUCN), had not distinguished between the two species of African elephants for purposes of assessing their conservation status. , the IUCN Red List classified African elephants as a whole as vulnerable species and the Central African elephant population (forest elephants) as Endangered.

Another possible species or subspecies formerly existed; although formally described it has not been widely recognized by the scientific community. The North African elephant (L. a. pharaohensis), also known as the Carthaginian elephant or Atlas elephant, was the animal famously used as a war elephant by Carthage in its long struggle against Rome.

Conservation
While the species is designated as vulnerable, conditions vary somewhat by region within East and Southern Africa.

In 2006, an elephant slaughter was documented in southeastern Chad by aerial surveys. A series of poaching incidents, resulting in the killing of over 100 elephants, was carried out during the late spring and summer of 2006 in the vicinity of Zakouma National Park. This region has a decades-old history of poaching of elephants, which has caused the population of the region, which exceeded 300,000 in 1970, to drop to about 10,000 today. The African bush elephant officially is protected by Chadian government, but the resources and manpower provided by the government (with some European Union assistance) have proven insufficient to stop the poaching.

Human encroachment into or adjacent to natural areas where the African bush elephant occurs has led to recent research into methods of safely driving groups of elephants away from humans, including the discovery that playback of the recorded sounds of angry honey bees are remarkably effective at prompting elephants to flee an area.