Proboscidea

Elephants

(Elephantidae)

Class Mammalia

Order Proboscidea

Family Elephantidae

Number of families 1

Thumbnail description
The largest living land animals, entirely herbivorous, characterized by the presence of a proboscis (trunk) and greatly elongated incisor teeth (tusks)

Size
Height at shoulder 6.5–13 ft (2–4 m); weight 2.2–7.7 tons (2–7 tonnes)

Number of genera, species
2 genera; 2 species (3 according to some authorities)

Habitat
Forest, savanna, and semi-desert

Conservation status
Endangered: 2 species

Distribution
Southern and Southeast Asia; Africa south of the Sahara

Evolution and systematics

The living elephant species are contained within a single family, the Elephantidae, and are the sole remaining representatives of the mammalian order Proboscidea. The name Proboscidea derives from the proboscis, or trunk; the name elephant derives from the Greek words for a large arch, referring to the elephant's arched back supported by pillar-like legs.

Both DNA and anatomical data indicate that the closest living relatives of elephants are the Sirenia—dugongs and seacows. Recently, it has become clear that elephants and sirenians fall within a larger grouping, including hyraxes, tenrecs, golden moles, elephant shrews (whose long nose is, however, independently acquired from that of the elephant), and the aardvark. Together, this diverse assemblage of mammals has been named "Afrotheria," since all are believed to have arisen in Africa from a common ancestor, 70 million or more years ago.

Approximately 165 fossil species of Proboscidea have been identified. The majority of early proboscidean fossils, 60–40 million years old, have been found in North Africa, and several of them appear to have been amphibious in habit. Moeritherium probably lived on a diet of aquatic plants, rather like a small modern day hippopotamus, which it resembled in build. Recent research has suggested that elephants retain some features reflecting a distant semi-aquatic ancestry. These include internal testicles, primitive embryonic kidney structures called nephrostomes, and the arrangement of the embryonic respiratory system. However, the suggestion that the trunk arose as a snorkeling device is probably not correct, as no living aquatic mammal has developed a "snorkel," and the trunk was only fully developed in later, fully terrestrial proboscideans.

In early Oligocene times, about 36–30 million years ago (mya), Palaeomastoden and Phiomia show the beginnings of an elephant-like appearance, with enlarged body size (up to about 6.5 ft [2m] shoulder height), distinct upper and lower tusks, and a short trunk. They may have been woodland browsers. The peculiar adaptive complex of features characterizing elephants developed during the course of proboscidean evolution. The increase in body size to massive proportions supported a huge gut for fermentation of large quantities of poor-quality forage. The massive molar teeth and heavy tusks are supported within a very large head and held on a very short neck, easing the task of raising and lowering it. But with a head high above the ground, short neck, and cumbersome tusks, feeding with the mouth (especially on low-growing plants) would be difficult; hence, the evolution of the trunk.

Among the diverse fossil proboscidean groups that evolved from about 25 million years onwards, the stegodons are the best known and regarded as the sister-group (closest relatives) of the elephants. Common fossils of Africa and Asia from

about 7–0.5 mya, the stegodon achieved tremendous size (11.5 ft; 3.5 m shoulder height) and sported extremely long, parallel, closely-spaced tusks.

True elephants (Elephantidae) are differentiated from their ancestors by detailed skull characters as well as by the loss of enamel covering the tusks, multiplication of enamel ridges on the molars, and heightening of the molar tooth crown. Since the earliest fossil representatives, 7–4 million years old, are found almost exclusively in Africa, it is reasonable to assume that the group originated there. Primelephas was the earliest member of the subfamily Elephantinae. It stood about as tall as a female Asian elephant, had upper and lower tusks, and is believed to have lived in an open wooded savanna.

Three great branches of the elephant family can be recognized in the fossil record of the last 4 million years or so. These are Elephas and its relatives (including the living Asian elephant), Loxodonta (including the living African elephants), and Mammuthus (including the woolly mammoth, not to be confused with the very distantly related but similarly named proboscidean Mammut, the American mastodont).

The earliest Loxodonta appears at 7.3–5.4 mya in Kenya and Uganda. It subsequently divided into two apparently coexisting species, L. adaurora and L. exoptata. The living species, L. africana presumably derived from one of these forms, and initially coexisted with a further species, L. atlantica, with grazing-adapted dentition and small tusks. The relationships among all these forms are unclear, but recent genetic evidence has cast new light on the history of the African elephant. The ancestors of the living species almost certainly lived in the forests of central Africa. Between about 3.5 and 2.5 mya, drying of the climate led to the development of savanna-adapted populations in the south and east. This division led to the modern subspecies, L. africana cyclotis (the forest elephant) and L. africana africana (savanna elephant). L. a. cyclotis is today the more primitive of the subspecies; its skull is similar to that of L. adaurora.

Today, the bush or savanna elephant, L. a. africana, is distributed in eastern and southern Africa, while the forest elephant, L. a. cyclotis, occupies much of central and western Africa. The physical differences between them are very marked. In L. a. africana, the body size is larger and rangier, the ears are very large and triangular, the tusks are massive and curve outwards

and forwards, and the back is distinctly saddle-shaped. In L. africana cyclotis, the body is distinctly smaller and more compact, the ears are smaller and rounded, the tusks are narrow, long, and downward-pointing, and the back is straighter.

These forms have been treated as subspecies of L. africana, but recent research has raised the possibility that they are separate species, L. africana and L. cyclotis. There are pronounced differences in skull and mandible anatomy, while DNA sequence studies found that forest elephants from central Africa were genetically quite distinct from those of the east and south African savannas, the genetic distance between the two groups being more than half as great as that between them and the Asian elephant. Finally, there are clear differences in habitat, feeding, social behavior, and communication. Hybridization, if it occurs at all, is limited and has not destroyed the integrity of the two forms.

However, the precise geographical limits of the two forms have yet to be established. Moreover, the forest elephants of West Africa, although they appear visually similar to L. a. cyclotis of central Africa, have been found to differ from them genetically. For these reasons, the IUCN's African Elephant Specialist Group decided in 2002 to provisionally retain the designations at subspecies level, pending further research, and this policy will be followed here. Thus, the elephants are named L. africana africana for the savanna elephants of southern and eastern Africa and the West African sahel, and L.

africana cyclotis for the forest elephants of central and West Africa. Records of the so-called pygmy elephant, L. pumilio, are almost certainly L. a. cyclotis.

The genus Elephas, leading ultimately to the E. maximus, the living Asian elephant, first appears as a fossil in Ethiopia 6.7–5.2 mya. This lineage produced a diversity of species in Africa, Europe, and Asia. The African Elephas ekorensis, from around 4.5–4 mya, appears to be close to the common ancestry of this radiation. Elephants entered Asia about 3 mya. One species, Elephas hysudricus, inhabited northern India and Myanmar between about 2 and 1 mya, and is believed to be close to the ancestry of E. maximus. E. hysudricus was of large size, massive tusks, and, like E. maximus, had a well-developed double head dome. There are remains of the hysudricus-maximus lineage about half a million years old in the Middle East, and by 120,000 years ago, E. maximus is recorded on Java. An earlier form on Java, E. hysudrindicus, lived from about 1 to 0.5 mya, but its skull and dental anatomy appear too specialized to have given rise to the living species.

A recent study of DNA sequences has identified two main genetic groups among Asian elephants. Although now widely dispersed and co-occurring in many areas, these may have originated in separate populations, one in Indonesia, and one on the mainland of Asia, which subsequently intermingled. Since the two genotypes are different enough to have separated a million or more years ago, researchers speculate that these two populations may be those identified in the fossil record as E. hysudricus (continental) and E. hysudrindicus (island Indonesia). This interesting theory must, however, be weighed against the anatomical differences between E. hysudrindicus and E. maximus as well as the observation that maximus replaced hysudrindicus on Java as part of a wave of colonization from the mainland.

There are three currently recognized subspecies of Elephas maximus: E. m. maximus of Sri Lanka and southern India, E. m. sumatrensis of Sumatra, and E. m. indicus throughout the rest of the range. The differences are a matter of degree and are expressed as gradual changes across the range. Elephants from Sri Lanka are the largest, have the darkest skin color, the largest ears, and are most prone to pink depigmentation of the skin on the face, trunk, and ears. Animals from Sumatra are the smallest, lightest in color, and least prone to depigmentation. Those in-between generally show

intermediate characters. However, there are exceptions: for example, elephants from western Nepal are perhaps the largest living anywhere today. And there are other particularities of the populations: most male elephants in Sri Lanka today are tusk-less, while the Sumatran subspecies is said to possess an extra pair of ribs (20 instead of 19 in the other subspecies).

Studies of Asian elephant genetics have not so far provided much insight into the systematics of the modern subspecies, probably due to genetic mixing resulting from the extensive historical movements of animals in captivity. In mitochondrial DNA, at least, there appears to be nothing distinctive about E. m. maximus of Sri Lanka, although the current population of Sumatra is genetically distinctive and may have been isolated for a hundred thousand years or more.

The mammoth was an elephant, and not the ancestor of living elephants but their cousin: the earliest mammoth fossils date from 4.5 to 4 mya in southern Africa and Ethiopia. Some time after that date, populations migrated north, arriving in Europe about 3 mya. They ultimately spread throughout northern Eurasia and North America, producing several species. The woolly mammoth, M. primigenius, probably arose in northern Siberia about 750,000 years ago in response to ice age conditions, later spreading to Europe and North America. Its adaptations included a furry coat, small ears and tail to prevent heat loss and frostbite, and teeth adapted to a grass-dominated diet.

There has been debate over the relationships among Elephas, Loxodonta, and Mammuthus. Anatomical studies of the skulls and other features initially suggested that Elephas and Mammuthus were more closely related to each other, and this was supported by some DNA sequence data. However, further studies of anatomy and DNA have cast doubt on this conclusion. Shared features of Elephas and Mammuthus, such as the higher skull and increased number of molar enamel bands, may have arisen independently, and the DNA data suggest that all three elephants may have diverged relatively close together some time in the interval 7–5 mya, a conclusion not inconsistent with the fossil record.

Physical characteristics

Elephants weigh 200–265 lb (90–120 kg) at birth. Unlike other mammals, they continue to grow well into adult life. Females cease growth at 25–30 years, males at 35–45. Adult weights range typically from 3.3 tons (3 tonnes) in a female Asian elephant, to 7.7 tons (7 tonnes) in a large African savanna bull; typical respective shoulder heights are 7.2–11.8 ft (2.2–3.6 m).

The elephant's head is proportionately very large, weighing up to half a ton/tonne; the neck is short. The body is supported on four extremely strong pillar-like legs. The elephant has five splayed toes buried within its foot, and stands on tiptoe; the first visible joint, some distance above the ground, is not the elbow or knee, but the wrist or ankle. The foot contains a pad of springy tissue that causes the elephant's foot to

swell sideways when it bears the animal's weight. The tail is long, extending to below the knee, and ends in a tuft of very coarse hairs. Otherwise, the body is sparsely covered by short hair, more pronounced in very young animals. As far as is known, there are no sweat glands. The ears are very large and thin, except for a thicker supporting ridge along the top. They are richly supplied with blood vessels for heat loss, and are flapped mainly for this purpose. The skin of both species is a uniform gray. Elephants may take on brown or other hues after wallowing in mud.

The elephant's trunk is, anatomically, a fusion between its nose and upper lip. The trunk is remarkably sensitive, flexible, and maneuverable, as well as being immensely strong. It contains no bone or cartilage, but is principally composed of muscle, in eight main sets (four on each side) comprising a total of about 150,000 separately moveable muscle units. Two nostrils run the entire length of the trunk for breathing.

The tusks are, anatomically, greatly expanded lateral incisor teeth. They are comprised almost entirely of dentine. About a third of their length is buried within a socket in the animal's skull. The tusks are solid, except the upper part within the socket, where there is a pulp cavity. The tusks grow by addition of dentine there, pushing them out by up to 6 in (15 cm) a year. The tusks of a large bull can extend 79 in (200 cm) in total length and weigh 110 lb (50 kg) each, although such figures are rare nowadays.

Distribution

The current range of the African elephant is Africa, south of the Sahara; it formerly extended into North Africa up to the Mediterranean coast. The Asian elephant currently occupies the Indian subcontinent and Southeast Asia, formerly extending from the Near East to the Pacific coast of China.

Habitat

Although occupying exclusively tropical and subtropical zones, elephants live in a wide range of habitats, including evergreen rainforests, dry deciduous forests, savannas (mixed woodland and grassland mosaics), and semi-deserts. They are essentially mixed feeders, so accessibility to a wide range of plants, and to water within one day's walk, are essential prerequisites.

Estimates of natural animal density are hard to make. The carrying capacity will also vary enormously with the environment. In general, an area of about 2 mi² (5 km²) per animal is probably typical in the wild, although the figure may be as high as 7.7 mi² (20 km²) in rainforest habitats.

In many areas where they live, elephants are the dominant mammalian species in terms of biomass, and have a major ecological role. Their massive dung production recycles nutrients back into the soil. They can disperse seeds and fruits over wide distances. Elephants seem quite resistant to the tannins present, for example, in acacia bark and, by consuming a wide variety of species, they limit the intake of toxic defensive compounds specific to particular plant types.

The elephants' habit of destroying trees has led to debate about their role in changing their own environment. In some parts of Africa, elephants have transformed wooded areas into open grassland. However, it is likely that in the formerly natural situation, such phenomena formed part of a natural cycle, with long-term balance between different habitats. If a high number of elephants in one area caused a reduction in the tree density, either the elephant population would limit its own reproduction, or the animals would migrate to another area, allowing regeneration of woodland. In some areas even today, vegetation regeneration seems to keep pace with elephant feeding; it is primarily in savanna habitats, and particularly where elephants have been constrained within the boundaries of reserves, that problems arise, and in the present situation these are certainly important issues for conservation. Many other factors such as fire and climate change also contribute to the balance between elephants and their habitats. In the severe drought of 1970–71, thousands of elephants died in Africa as a result of food and water shortage.

Behavior

The understanding of the complex social lives of elephants has been built up thanks to long-term studies over 20 or 30 years by dedicated field researchers, notably Cynthia Moss and colleagues in East Africa, and Raman Sukumar in India. By learning to recognize individual animals, much has been learned about social organization and the factors influencing the status and success of families and individuals.

Elephant society has a structure that has been termed matriarchal. The core element is the family unit, a group of 3–25 individuals, comprising related adult females and their young. Females within the family unit are closely bonded for life. By contrast, adult males tend to be solitary, or may form temporary associations of two or three unrelated bulls. They leave the family of their birth at 12–15 years of age and, after that time, although they may frequently associate with female groups for feeding or mating, they have no long-term bonds with them, or with each other.

Within the female groups, a few older individuals, and in particular the lead individual, termed the matriarch, are instrumental in deciding the group's pattern of movement, in defending the group against danger, and in monitoring and responding to other approaching elephants. Calves, especially when very young, stay close to their mother, but all females in the group will aid in its upbringing. At the approach of a predator, adult females wheel round to face the source of danger, protecting the calves that stay close behind. The members of a family unit may separate for short intervals during the day, but will soon regroup. Family units also form looser associations or "bond groups," with more distantly related families. Occasionally, very large herds of 500 or even 1,000 elephants can be seen, primarily during migration. Even then, within the mass of animals, individual family groups maintain their integrity.

Elephants are highly intelligent animals with a complex repertoire of social interactions. Within a family group, individuals of all ages greet, and maintain bonding, by touching their trunk tips to each other's bodies, rubbing together, and with sound communication and scent. In calves, play is a dominant behavior. They mock charge, chase each other, or wrestle with their trunks. Males, from an early age, engage in mock sparring matches. They are also more independent of their mothers than the females, a trend that increases as they get older.

There is a dominance hierarchy among bulls, generally related to their age, size, and power. If two bulls of roughly equal size meet, they may assess each other through intertwining trunks, pushing and pulling, or lightly engaging their tusks. Rarely, sparring may lead to a full-scale fight, sometimes (but not always) for access to an oestrus female. The combatants will charge each other with ears outstretched, or cross tusks and attempt to twist the opponent off-balance, all accompanied by loud vocalizations. Each tries ultimately to gore the other with his tusks, sometimes resulting in fatal wounds by deep penetration of the head or chest. Broken tusks may result from twisting with the full body weight. The fight

will end either by withdrawal of the weaker animal, or with death.

Male elephants enter a periodic state called "musth." The temporal gland, located on the side of the head between the ear and the eye, produces a dark musky fluid (temporin) with a strong, musky odor. Musth males also intermittently dribble urine. A male elephant generally enters musth once a year, for a period of anything up to a month, the time of year varying with the animal. Musth bulls have heightened levels of testosterone and are very aggressive, especially toward other bulls. Musth is associated with heightened sexual activity, although non-musth bulls also mate. Females also have a temporal gland, which can occasionally be seen to ooze secretion, and elephants have been observed rubbing their cheeks against trees, so temporin may have broader communication functions. Recent research has indicated that subordinate bulls produce a different chemical signal, with a sweet aroma, which may be used to signal submissiveness to the dominant bulls and so avoid attack.

Elephants have relatively poor vision, but highly developed senses of taste and smell. They obtain chemical cues by using their trunks to touch each other's genitals, mouths, temporal glands, dung, and urine. They also often lift their trunks and rotate the open tips, testing the air for the scent of other animals in the vicinity. It is very likely that they can identify different individual elephants from these cues.

Elephants also have acute hearing and communicate through a wide variety of vocalizations. At least 25 different calls, audible to the human ear, have been identified in African elephants, 15 of them in a low-frequency group termed rumbles. Some of them are known to be associated with different events such as musth in a bull and oestrus or copulation in a female. In addition, a range of infrasound vocalizations extends down to 5 Hz, well below the frequency of human hearing. Low-frequency sound is less subject to environmental attenuation, and elephant rumbles and infrasound are audible to other elephants over a range of up to 3 mi (5 km). It has also been suggested that elephants may communicate over even longer distances as they stamp their feet on the ground; this theory remains to be tested.

An elephant can live to around 60 years; many die before this age, from disease, injury, starvation, drought, or predation (though the latter is rare for healthy adult animals). A remarkable aspect of elephant behavior is their response to injured, sick, and dead members of their species. Many accounts have been recorded: adult females immediately circling around a wounded animal to prevent further attack; lifting a wounded animal to its feet and shouldering it away to safety; jumping into water where a wounded animal has fallen, and heaving it out again; pulling and pushing a calf out of mud where it had become stuck; standing guard over a stricken, but living, animal lying on the ground; covering the body of the relative with grass and leaves as soon as it had died; returning to the carcass or even skeleton of a dead relative; and tasting, picking up, and moving the remains with their trunks.

The idea of an elephant graveyard, a place where elephants go to die, is a myth. Sick and dying elephants often go to a lakeside or river, where there is a ready supply of food and water within easy reach, and several might die in one area for that reason. In times of drought, animals congregate around water holes and many may die there.

Elephants are not territorial. Although individuals or family units have home ranges, those of different animals overlap and are not defended as such. There are daily and seasonal activity patterns within the home range. They sleep lying down, usually for two to four hours in the early morning. They may also, in the hottest part of the day, stand motionless in the shade, but even when the eyes are closed, they are most likely dozing rather than sleeping.

Seasonal movements, especially in open country, may see large aggregations of hundreds of animals. In other situations, particularly in forest environments, matriarchs lead their families along the same paths that have been used for generations; these elephant trails, trampled, barren ground 3–6 ft (1–2 m) wide, can extend for tens of miles (kilometers).

Elephants walk or amble, but cannot canter or gallop. A charging animal can attain 16 ft (5 m) per second, or 12.4 mph (20 kph), while walking speed ranges 1.6–8.2 ft (0.5–2.5 m) per second, or 1.2–6.2 mph (2–10 kph). Elephants walk cautiously, appearing to place each foot with care to avoid ground that is too soft or cobbled, for example. Even so, they can maneuver very dense terrain and can climb up and down remarkably steep, slippery slopes. They are also adept swimmers, paddling with all four feet and using the trunk as a snorkel.

Feeding ecology and diet

Elephants consume a huge range of plant types, including grasses, herbs (forbs), shrubs, broadleaved trees, palms, and vines. Depending on the plant, they can take every conceivable part, including leaves, shoots, twigs, branches, bark, flowers, fruit, pods, roots, tubers, and bulbs. The range of plants taken by an elephant can be anything between 100–500 species, although in a given time and place the animals may concentrate on a few species.

Patterns of consumption change with the seasons. In the savanna-woodland habitats of Africa, and in the dry forests of Asia, new growth grasses are favored in the rainy season, comprising 50–60% of the diet, but as these become tough in the dry season, the elephants switch to browse, so that the leaves and fruit of trees and shrubs now comprise 70% of the intake. In the forests of Asia, bamboo is an important component throughout the year. For elephants in rainforest habitats such as those of central Africa and Malaysia, for example, the

year-round supply of succulent leaves and fruits ensures that grass plays a lesser part in their diet.

Tree bark is eaten because it provides essential minerals and fatty acids, as well as roughage. Elephants also frequent salt licks, those patches of soil or exposed rock high in minerals such as sodium.

Food consumption is 220–660 lb (100–300 kg) per day. Elephants spend 12–18 hours per day eating, most intensively in the morning and in the late afternoon to evening. In food-rich forest areas, elephants will typically move slowly through the day, browsing on a variety of plants, and eventually covering several miles (kilometers). In many areas, there are daily rhythms: where both woodland and open grassland are available, for example, the elephants may spend the morning and early afternoon browsing in the woodland, emerging in the cool of the late afternoon to graze. Fluid consumption can be 53 gal (200 l) of water per day in hot weather. When water is scarce, elephants will dig holes in dry stream or lake beds, using their feet, trunk, and tusks, until water seeps in and can be sucked up.

When plants become ready at particular times of year, such as fruits or new shoots, elephants will gravitate towards them, using both smell and a memory from past years. Generally speaking, the poorer the quality, abundance, or predictability of food and water, the greater the distances elephants must travel to find it. Home ranges, measured by radio-collaring individuals, vary from 23 mi² (60 km²) in a rich rainforest habitat in Malaysia, to 1,158 mi² (3,000 km²) in the Namib Desert, where individuals can easily walk 50 mi (80 km) in a day. In many areas, migrations are seasonal. Where water is a key issue, elephants tend to accumulate in the dry season in areas it can be found, dispersing more widely when this constraint is lifted during the wet season.

Small items can be plucked or picked up with the terminal "fingers" of the trunk, the larger items, such as branches, by curling the trunk around them and pulling or twisting. Elephants are highly inventive and can be seen, for example, kicking up sods of dry turf with their feet, picking up the resulting grassy clump with the trunk, banging it against their leg to shake off the earth, and putting in the mouth. To reach high branches where young, succulent leaves are to be found or up in acacia trees, which have fewer thorns, they can rear up on their back legs, giving a total reach of up to 26 ft (8 m). They will also uproot or push over trees. Finally, the trunk is important in drinking; water is not sucked all the way up into the nose like a drinking straw, but is sucked into the lower part of the trunk, then the trunk is arched and water squirted into the mouth. The capacity of an Asian elephant's trunk has been measured at 2.2 gal (8.5 l). The only time in its life when an elephant feeds directly with its mouth is when suckling, the mouth being pressed directly against the breast with the trunk curled up out of the way.

The tusks are used to strip bark from trees, which is then eaten; to dig for roots or for water in the dry season; and to scrape or hack salt and other minerals from the soil or exposed rock.

The molar teeth display a series of long, thin enamel ridges running side to side; for this reason, an elephant chews by swinging its lower jaw fore and aft, so that the enamel ridges on the upper and lower teeth cut past each other, shearing the food. The tremendous wear caused by feeding long hours every day on abrasive food causes the teeth to grind down to the root, and elephants not only have high-crowned teeth, but replace their teeth five time through their life, making six sets in all. Each set, however, comprises only four massive teeth, lower and upper, left and right. As one tooth wears out, it moves forward in the jaw and is gradually replaced by another from behind.

The majority of an elephant's digestion is accomplished with the aid of cellulose-digesting microorganisms inhabiting its large intestine, especially a large blind sac opening from it, the cecum. This is a relatively inefficient method of digestion—only 40% or so of food, by weight, is utilized— but it does allow the animal to process large quantities of relatively low-nutrient food. The intestine is up to 115 ft (35 m) long and may weigh up to a ton (0.9 tonnes) when full of food, releasing an average of 220 lb (100 kg) of dung per day.

Reproductive biology

Elephant reproduction is slow; a female gives birth only every four to five years or so, and usually to one calf at a time, though twinning occurs in roughly one in 100 births. Growth to adulthood is also a long process. In consequence, a tremendous amount of time and energy is expended in the rearing of the young, a task that falls entirely to the females.

Elephant cows become sexually mature at the age of 12–14, and begin to reproduce soon after that date. Bulls start producing sperm around the same time, but in practice rarely father any calves until they are approaching 30.

Female elephants come into estrus about every 16 weeks, and are sexually receptive for only a day or so during this period, so male and female behavior must be tightly attuned. A male, especially when in musth, will visit female groups, testing for estrus females by touching their vulvas with the tip of his trunk. He then touches his trunk tip on a specialized taste gland, the Jacobson's organ, on the roof of his mouth. It has recently been discovered that the females' urine contains a pheromone indicating that she is in oestrus. She will also signal her readiness by behavioral cues. Copulation begins when the male reaches over the female's shoulder with his trunk from behind. The female exerts some choice in the matter, and may run off even at this stage. Otherwise, the bull mounts, placing most of his weight on his back legs. The penis is S-shaped, up to 3.2 ft (1 m) long, and highly muscular, finding and entering the vulva without pelvic movement. The testes are internal (unusual in mammals) and situated near the kidneys; up to 1 qt (1 l) of ejaculate is produced. The bull will remain with the female for anything from a few hours to a few days, mating with her occasionally and guarding her from the advances of rival males.

Pregnancy lasts about 22 months, and birth, accomplished with the mother squatting or lying, is assisted by other females of the group. The two mammary glands are situated between the front legs (unusual for quadrupedal mammals). Calves suckle until the second or third year or even longer, depending on when the next calf is born. Male calves suckle more frequently than females and, after the first few years, the difference in size between them becomes apparent. Female calves will remain in their family unit for life, eventually taking over its leadership, while males leave at sexual maturity, often aided by increasing impatience of the mother.

In drought years, cows are unlikely to come into oestrus, naturally regulating their reproduction. Otherwise, they can conceive at any time of year, but in seasonal environments, a definite peak has been observed some weeks after the onset of the rains. With a 22-month gestation, this ensures that the calf will be born when rainy-season greening has begun two years later, providing the mother with a rich food supply for lactation.

Conservation status

Elephants are faced with a dual threat to their survival: the destruction of their habitat, and hunting. The former is common to many species; the latter is due to the elephant's possession of a precious commodity: ivory.

Habitat destruction has both reduced the total range of elephants, and has greatly fragmented it within human settlement and agriculture. The principal cause is human population growth, but also activities such as logging for financial gain. Over much of the range, the remaining habitats correspond to national parks, nature reserves, and the like. Many of these fragments retain less than 100 individuals and prospects for their long-term survival are not good. If there is no exchange of individuals with other populations, inbreeding reduces the genetic health of the population. If climatic fluctuations produce a series of stressful years, the population will suffer increased mortality and reduced birth rate, and may not recover. In West Africa through the 1980s, elephant populations in habitat fragments of less than 96 mi² (250 km²) had only a 20% chance of surviving the decade, while those in areas of more than 290 mi² (750 km²) had almost a 100% chance of survival.

The hunting of elephants for meat has been practiced since prehistoric times, but only with the use of firearms has the thirst for ivory posed a threat to the very survival of the species. By 1800, the elephant populations of southern and West Africa had already been seriously depleted. A century later, the trade from Africa alone had increased to 1,100 tons (1,000 tonnes) per year. The 1970s and 1980s proved critical: the total African population fell from an estimated 1.3 million animals in 1979, to just over 400,000 in 1987. Asian elephant populations have also suffered at the hand of humans, both through ivory hunting and the gathering of wild animals for domestic use. The effect of ivory hunting on the two species is somewhat different, since in the African elephant both males and females carry tusks and are hunted, while in the Asian species only the males have ivory. This has led to

a situation in some parts of Asia where the natural female-to-male ratio of 2:1 has risen to anything from 5:1 in the best-protected areas, to 100:1 in the worst; in the latter cases, the survival of even sizeable populations is threatened because of lowered reproductive rate.

From its foundation in the 1970s, CITES placed Asian elephants on its Appendix I and African elephants on Appendix II. In 1989, however, the African elephant was raised to Appendix I, effectively banning all trade in elephant ivory. The policy worked: ivory prices fell, and many countries reported a drastic reduction in poaching. However, in 1997, some southern African countries with healthy elephant populations won from CITES the permission to sell ivory stocks. The market was stimulated, and in subsequent years, increased poaching has been reported by a number of African countries. Nonetheless, in 2002, CITES agreed to allow further sales of stockpiled ivory by these countries, despite almost universal opposition from conservation organizations. Combating the ivory trade is a complex issue that requires the enforcement not only of bans against hunting, but international action to trace both the organizers of poaching, the middle men, and the ultimate consumers.

The management and protection of elephant habitats is also a major goal, especially in Asia. International support enabling poor countries to maintain existing wildlife reserves, or to create new ones, is crucial. Properly managed ecotourism can be beneficial, as it provides an income underscoring the value of the reserve. Yet small reserves, even when protected, may not support enough animals to give a viable population. Raman Sukumar has suggested that 50 breeding individuals, translating into 125–150 animals, is a minimum goal, with 10 times that number an ideal. One solution to this problem is to create corridors of habitat, allowing animals to migrate between parks, so that populations are effectively merged into one, viable unit.

Elephant-human conflict is a serious issue in some areas. Elephants enter agricultural areas and can destroy the entire crop of a smallholding in a single night. They also damage buildings and annually kill dozens of villagers in Asia. Traditional countermeasures include lighting flares, throwing rocks, employing domestic elephants to chase away the marauders, or digging trenches around fields. The latter are of some use but elephants learn how to fill them with earth or logs. Electric fences are employed by rich landowners, but are too expensive to bound large national parks or small private holdings. Other measures include not planting crops favored by elephants in the area around their habitat, and relocating farms and villages (with compensation paid to the farmers). The latter may also be necessary when extending reserves or creating habitat corridors.

In some African countries, elephant populations in wildlife parks have been held in check by government-approved culling. The stated rationale is to prevent the populations increasing to the point where they turn woodland into grassland, reducing biodiversity, and leading to elephant mortality when drought hits, as happened in Tsavo National Park, Kenya, in the 1960s and 1970s. Opponents counter that culling (sometimes of entire family groups) is inhumane and causes stress to surviving animals; is a temptation for illicit ivory dealing; interferes with natural cycles; and depresses tourism. Possible alternatives include relocating animals to areas of low density and subcutaneous implants of birth-control hormones.

Current estimates of world population size are between 34,000 and 54,000 wild Asian elephants, with roughly 13,000–16,000 in captivity. For the African elephant, the latest estimate is between 300,000 and 500,000 animals.

Significance to humans

Elephants, especially in Asia, have a long history of interaction with people, and an important place in many cultures. Ivory carving has been practiced since at least 30,000 years ago, when Palaeolithic people in Europe made tools and ornaments out of mammoth tusk. Ivory is hard, fine-grained, and has an elasticity that makes it excellent for carving: skilled craftspeople can produce objects of great beauty. Countless functional objects have been made throughout history: in recent centuries, piano keys and billiard balls were one of the main uses in the West, and in recent decades, the ornamental "signature seal" of Japan has become a major end-product.

The earliest evidence of elephant domestication is in the third millennium b.c. in the Indus Valley of India. The initial domestication was probably for purposes of traction, tree felling, and portage; this usage continues today in parts of Southeast Asia, although it is declining. Elephants were formerly captured from the wild, either singly in pits, or as family units in stockades; now they are bred and trained from calves. An elephant can recognize and respond to 30 or more commands issued by its mahout, or driver.

Soon after their domestication, elephants were pressed into military service. In 326 b.c., the Indian king Porus, with 200 elephants in his army, was famously defeated by Alexander. A typical battle formation of the Vedas included 45 elephants, which were the first to charge, throwing the enemy into disorder and knocking down stockades. Kings and princes hunted from elephant-back, a practice taken over with enthusiasm by European colonizers. In general, elephants came to embody royalty, largely because of the high price of their capture and maintenance.

The elephant also plays a prominent part in the Hindu pantheon. Airavata was the elephant mount of Lord Brahma, creator of the universe. Two elephants were the massive pillars of the world and bore the earth on their enormous heads. Ganesh, the elephant god, is one of the best loved of all Hindu deities: as the Remover of Obstacles and Lord of Beginnings, he is invoked at the start of any undertaking. The worship of Lord Ganesh originated in the third or fourth century a.d. and created a strong ethos against the killing of elephants. In Buddhist countries, especially in Indochina, the very rare white elephant was revered as an incarnation of the Buddha; when captured, it was ministered to with the utmost care.

The comparative rarity of domestication in African elephants appears to be for human cultural reasons rather than any innate inability of the species to be domesticated. The Carthaginians fought the Romans with them, and Hannibal's famous crossing of the Alps was probably with the African species. In modern times, Belgian colonizers domesticated elephants for traction and other uses in Central Africa.

Species accounts

List of Species

Asian elephant

Elephas maximus

subfamily

Elephantinae

taxonomy

Elephas maximus Linnaeus, 1758, Sri Lanka.

other common names

English: Indian elephant; French: Eléphant d'Asie, eléphant asiatique; German: Asiatische Elefant; Spanish: Elefante asiático.

physical characteristics

Weight 3.3–5.5 T (3–5 t), shoulder height 6.6–9.8 ft (2–3 m), back convex, high double head domes, ears smaller than African species, fold forwards at top, one finger at tip of trunk. Pigment loss with age, resulting in pink speckling of the ears and eventually of the face and trunk: particularly noticeable in E. m. maximus of Sri Lanka. Hairier than African species. Only males bear tusks, although females frequently possess tiny tusks called "tushes," which can just be seen protruding form the lip, especially when the trunk is raised. A percentage (currently increasing) of males congenitally lack tusks: known as "mukhnas," these animals are thought to compensate by being especially strongly-built, especially in the upper trunk region.

distribution

Principally in Burma, Cambodia, India, Indonesia (Sumatra), Laos, Malaysia, Sri Lanka, Thailand, and Vietnam, with small populations (fewer than 500 individuals) in Bangladesh, Bhutan, southwest China, Indonesia (Kalimantan), and Nepal. About half the world population is in India, and half of that in the southwest of the country. The principal characteristic of the global distribution is its fragmentation.

habitat

Wet evergreen forest, montane evergreen forest and grassland, semi-evergreen forest, moist deciduous forest, dry deciduous forest, savanna woodland, bamboo forest, dry scrub, and swampy floodplain grassland.

behavior

May spend as much as 18–20 hours a day feeding. Very social, with a matriarchal structure: the oldest female is instrumental in deciding the group's movements. There is a dominance hierarchy among bulls; they tend to be solitary. This species is not territorial.

feeding ecology and diet

Adult food consumption is 220–440 lb (100–200 kg) per day. In mixed habitats, averaged over the season, approximately 50/50 browse and graze taken. Molars with greater number of enamel ridges than African elephant.

reproductive biology

Pregnancy slightly less than 22 months; birth weight 198 lb (90 kg). Courtship behavior includes female standing face to face and intertwining trunks with the male. Males are competitive.

conservation status

Listed as Endangered by the IUCN, and on Appendix I of CITES.

significance to humans

Highly important in cultures of southern Asia. Revered in religion, though captured for domestic work and warfare.

African elephant

Loxodonta africana

subfamily

Elephantinae

taxonomy

Loxodonta africana (Blumenbach, 1797), Orange River, South Africa. Two subspecies.

other common names

French: Eléphant d'Afrique, eléphant africain; German: Der Afrikanische Elefant; Spanish: Elefante Africano.

physical characteristics

L. a. africana: weight 4.4–7.7 T (4–7 t), shoulder height 8.2–13 ft (2.5–4 m), back concave; L. a. cyclotis: weight 2.2–4.4 T (2–4t), shoulder height 6–9.8 ft (1.8–3 m), back straighter. Head less high than Asian species and single domed, ears larger and fold back at top, two fingers at end of trunk. Both sexes possess tusks, those of the female being relatively smaller.

distribution

Occurs in about 35 African states. In West Africa, only thinly scattered, small populations remain, mostly L. a. cyclotis; northernmost Sahel population (Mali) probably a western extension of L. a. africana. Central African rainforests: still substantial, largely continuous, populations of L. a. cyclotis. East and southern African savannas down to northernmost Namibia, Botswana, Zimbabwe, and South Africa (with large hole in central Angola and neighboring areas): L. a. africana.

habitat

L. a. africana: woodland, shrub and tree savanna, floodplain grassland, and desert; L. a. cyclotis: evergreen rainforest, moist semi-deciduous forest, woodland, and forest/grassland margins.

behavior

L. a. africana, at least historically, had a tendency to aggregate in large herds, especially for seasonal migration. Social matriarchal society.

feeding ecology and diet

Daily adult food consumption 220–660 lb (100–300 kg). Molar teeth with fewer, lozenge-shaped enamel bands.

reproductive biology

Female signals oestrus by a special walk, with the head held high while looking back over her shoulder, as well as loud vocalizations. In courtship, female's movements include spinning round and leading the male on a mock chase. Males are competitive. Gestation period is 22 months. Birth weight 265 lb (120 kg).

conservation status

Listed as Endangered by the IUCN, and on CITES Appendix I, except some southern African countries; moved to Appendix II in 2002.

significance to humans

Hunted for meat and ivory. Rarely domesticated.

Resources

Books

Buss, Irven O. Elephant Life: Fifteen Years of High Population Density. Ames IA: Iowa State University Press, 1990.

Delort, Robert. The Life and Lore of the Elephant. London: Thames and Hudson; New York: Harry N. Abrams, 1992.

Eltringham, S.K., ed. The Illustrated Encyclopaedia of Elephants. New York: Crescent Books, 1991.

Lister, Adrian, and Paul Bahn. Mammoths: Giants of the Ice Age. London: Marshall Editions, 2000.

Moss, Cynthia. Elephant Memories: Thirteen Years in the Life of an Elephant Family. University of Chicago Press, 2000.

Payne, Katy. Silent Thunder: The Hidden Voice of Elephants. Phoenix: Wiedenfeld and Nicholson, 1999.

Shoshani, Jeheskel, and Pascal Tassy, eds. The Proboscidea: Evolution and Palaeoecology of Elephants and their Relatives. Oxford: Oxford University Press, 1996.

Shoshani, Jeheskel, ed. Elephants. London: Simon & Schuster, 1992.

Periodicals

Eggert, Lori S., et al. "The Evolution and Phylogeography of the African Elephant Inferred from Mitochondrial DNA Sequence and Nuclear Microsatellite markers." Proceedings of the Royal Society of London B 269 (2002): 1993–2006.

Fleischer, Robert C., et al. "Phylogeography of the Asian Elephant (Elephas maximus) Based on Mitochondrial DNA." Evolution 55 (2001): 1882–1892.

Grubb, Peter, et al. "Living African Elephants Belong to Two Species: Loxodonta africana (Blumenbach, 1797) and Loxodonta cyclotis (Matschie, 1900)." Elephant 2, no.4 (2000): 1–4.

Maglio, Vincent J. "Origin and Evolution of the Elephantidae." Transactions of the American Philosophical Society 63, no. 2 (1973): 1–149.

Thomas, M. G., et al. "Molecular and Morphological Evidence on the Phylogeny of the Elephantidae." Proceedings of the Royal Society of London B 267 (2000): 2493–2500.

Other

Elephant Information Repository. <http://elephant.elehost.com>

African Elephant Specialist Group (AfESG) of the IUCN. <http://iucn.org/themes/ssc/sgs/afesg>

African Elephant (Loxodonta africana). Eleventh Meeting of the Conference of Parties to CITES. Nairobi, 10–20 April 2000. <http://www.panda.org/resources/publications/species/cites/fs_afeleph.html>

Elefriends Campaign. Born Free Foundation. <http://www.bornfree.org.uk/elefriends>

Adrian Lister