Eukaryota

African elephants are the species of elephants in the genus Loxodonta (Greek for 'oblique-sided tooth'^[3]), one of the two existing genera in Elephantidae. Although it is commonly believed that the genus was named by Georges Cuvier in 1825, Cuvier spelled it Loxodonte. An anonymous author romanized the spelling to Loxodonta and the ICZN recognizes this as the proper authority.^[1]

Fossil members of Loxodonta have only been found in Africa, where they developed in the middle Pliocene.

Size

African elephants are bigger than Asian elephants. Males stand 3.2–4.0 m (10–13 ft) tall at the shoulder and weigh 4,700–6,048 kg (10,000–13,330 lb), while females stand 2.2–2.6 m (7.2–8.5 ft) tall and weigh 2,160–3,232 kg (4,800–7,130 lb).^[4]

Teeth

A male African bush elephant in Namibia

Elephants have four molars; each weighs about 5 kg (11 lb) and measures about 30 cm (12 in) long. As the front pair wears down and drops out in pieces, the back pair shifts forward, and two new molars emerge in the back of the mouth. Elephants replace their teeth six times. At about 40 to 60 years of age, the elephant no longer has teeth and will likely die of starvation, a common cause of death.

Their tusks are teeth; the second set of incisors become the tusks. They are used for digging for roots and stripping the bark off trees for food, for fighting each other during mating season, and for defending themselves against predators. The tusks weigh from 23–45 kg (51–99 lb) and can be from 1.5–2.4 m (5–8 ft) long. Unlike Asian elephants, both male and female African elephants have tusks.^[5] The enamel plates of the molars are fewer in number than in Asian elephants.^[6]

Species

• African bush elephant (Loxodonta africana).^[1]
• African forest elephant (Loxodonta cyclotis).^[1]
• Loxodonta adaurora, extinct, presumed antecedent of the modern African elephants.^[3]
• Loxodonta atlantica, extinct.^[3]
• Loxodonta exaptata, extinct.^[3]

Bush and forest elephants were formerly considered subspecies^[7] of the same species Loxodonta africana. As described in the entry for the forest elephant in the third edition of Mammal Species of the World (MSW3),^[8] there is now morphological and genetic evidence they should be considered as separate species.^[9][10]

Females usually live in smaller or larger herds, here Loxodonta africana in Tanzania

Much of the evidence cited in MSW3 is morphological. The African forest elephant has a longer and narrower mandible, rounder ears, a different number of toenails, straighter and downward tusks, and considerably smaller size. With regard to the number of toenails: the African bush elephant normally has four toenails on the front foot and three on the hind feet, the African forest elephant normally has five toenails on the front foot and four on the hind foot (like the Asian elephant), but hybrids between the two species commonly occur.

MSW3 lists the two forms as full species^[1] and does not list any subspecies in its entry for Loxodonta africana.^[11] However, this approach is not taken by the United Nations Environment Programme's World Conservation Monitoring Centre nor by the International Union for Conservation of Nature (IUCN), both of which list L. cyclotis as a synonym (not even a subspecies) of L. africana.^[12][2]

A consequence of the IUCN taking this view is that the IUCN Red List makes no independent assessment of the conservation status of the two forms of African elephant. It merely assesses the two forms taken together as a unit as vulnerable.^[2]

A study of nuclear DNA sequences published in 2010 indicated that the divergence date between forest and savanna elephants is 2.6–5.6 million years ago, which is virtually the same as the divergence date estimated between the Asian elephant and woolly mammoths (2.5–5.4 million years ago), strongly supporting their status as separate species. Forest elephants were found to have a high degree of genetic diversity, perhaps reflecting periodic fragmentation of their habitat during the climatic changes of the Pleistocene.^[13]

Conservation

Men with African elephant tusks, Dar es Salaam, c. 1900

Poaching significantly reduced the population of Loxodonta in certain regions during the 20th century. An example of this poaching pressure is in the eastern region of Chad—elephant herds there were substantial as recently as 1970, with an estimated population of 400,000; however, by 2006 the number had dwindled to about 10,000. The African elephant nominally has governmental protection, but poaching is still a serious issue.^[14]

Human encroachment into or adjacent to natural areas where bush elephants occur 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 is remarkably effective at prompting elephants to flee an area.^[15] Some elephant populations have grown so large that some African communities have resorted to culling large numbers to help sustain the ecosystem.^[16]

See also

Ivory trade

References