Elephas maximus Linnaeus, 1758

Size and Body Shape

The Asian elephant (Elephas maximus Linnaeus, 1758) is generally smaller than the African bush elephant, with its highest body point located on the head. Its back is either convex or level.

Ear and Skeletal Features

It has small ears with dorsal borders folded laterally, up to 20 pairs of ribs and 34 caudal vertebrae. Each forefoot has five nail-like structures, and each hind foot has four.

Head and Forehead Structure

Unlike the flat front of African elephants, the Asian elephant’s forehead has two hemispherical bulges. Its long trunk (proboscis) has only one fingerlike tip, compared to the two tips of African elephants.

Trunk Feeding Behavior

Because of this, Asian elephants rely more on wrapping around food items and squeezing them into their mouths instead of grasping with the trunk tip, and they have greater muscle coordination that allows them to perform more complex tasks.

Tusk Presence in Females

Female Asian elephants (cows) usually do not have tusks; if small tusks (called "tushes") are present, they are barely visible and only seen when the mouth is open.

Tusk Presence in Males

Some males (bulls) may also lack tusks; these tuskless individuals are called "makhnas" and are especially common among the Sri Lankan elephant population.

Recorded Tusk Sizes

Recorded tusk sizes vary: a tusk from an 11 ft (3.4 m) tall elephant killed by Sir Victor Brooke measured 8 ft (2.4 m) long, nearly 17 in (43 cm) in circumference, and weighed 90 lb (41 kg). This weight was exceeded by a shorter tusk around 6 ft (1.8 m) long that weighed 100 lb (45 kg), and there are reports of tusks weighing over 150 lb (68 kg).

Skin Color and Texture

Asian elephant skin is usually grey, and may be covered by soil from dusting and wallowing. Their wrinkled skin is movable, contains many nerve centers, and is smoother than the skin of African elephants.

Skin Depigmentation and Thickness

Depigmentation may occur on the trunk, ears, or neck. The average combined thickness of the epidermis and dermis across the body is 18 mm (0.71 in); skin on the dorsum is 30 mm (1.2 in) thick, providing protection against bites, bumps, and adverse weather.

Skin Function

Skin folds increase surface area to help with heat dissipation. Asian elephants tolerate cold better than excessive heat.

Body Temperature

Their skin temperature ranges from 24 to 32.9 °C (75.2 to 91.2 °F), and average body temperature is 35.9 °C (96.6 °F).

Global Distribution Range

Asian elephants are distributed across the Indian subcontinent and Southeast Asia, ranging from India in the west to Borneo in the east, and from Nepal in the north to Sumatra in the south.

Habitat Types

They inhabit grasslands, tropical evergreen forests, semi-evergreen forests, moist deciduous forests, dry deciduous forests, dry thorn forests, as well as cultivated areas, secondary forests, and scrublands.

Elevation Range

Across these habitat types, elephants occur from sea level up to over 3,000 m (9,800 ft). In the eastern Himalaya of northeast India, they regularly move to elevations above 3,000 m (9,800 ft) in summer at a few sites.

Bangladesh Population

In Bangladesh, some isolated populations survived in the southeast Chittagong Hills in the early 1990s.

Malaysia Population Movement

In Malaysia’s northern Johor and Terengganu National Park, two satellite-tracked Asian elephants spent most of their time in secondary or logged-over forest, and traveled 75% of the time within an area less than 1.5 km (0.93 mi) from a water source.

China Population Status

In China, Asian elephants only survive in the prefectures of Xishuangbanna, Simao, and Lincang in southern Yunnan; as of 2020, the estimated population there was around 300 individuals.

India Population Estimates

As of 2017, India’s estimated wild population made up nearly three-fourths of the world’s extant Asian elephant population, at 27,312 individuals. In 2019, India’s Asian elephant population was estimated to have increased to between 27,000 and 29,000 individuals.

Global Population Estimate

As of 2019, the global wild population was estimated at 48,323 to 51,680 individuals.

Activity Pattern

Asian elephants are crepuscular.

Feeding Rate and Diet

They are classified as megaherbivores and consume up to 150 kg (330 lb) of plant matter per day, with around 50 to 75% of each day spent eating. They are generalist feeders that act as both grazers and browsers, and have been recorded feeding on at least 112 different plant species.

Common Food Plant Groups

The most commonly consumed plants belong to the order Malvales, as well as the legume, palm, sedge, and true grass families. They browse more often in the dry season, and bark makes up a major part of their diet during the cool part of this season.

Water Requirements

They drink at least once a day and are never far from a permanent source of fresh water. They need 80 to 200 litres of water a day, and use even more for bathing.

Mineral Intake

They will sometimes scrape soil to obtain clay or minerals.

Social Group Structure

Cows and calves travel together in groups, while bulls disperse from their mothers when they reach adolescence. Bulls are either solitary or form temporary "bachelor groups".

Cow-Calf Unit Size

Cow-calf units are generally small, typically consisting of three adult (most likely related females) and their offspring, though larger groups of up to 15 adult females have also been recorded. Seasonal aggregations of 17 individuals including calves and young adults have been observed in Sri Lanka’s Uda Walawe National Park.

Social Organization Research

Until recently, Asian elephants were thought, like African elephants, to be led by older adult females called matriarchs. It is now recognized that cows form extensive, very fluid social networks with varying degrees of association between individuals, and social ties are generally weaker than those of African bush elephants.

Limb and Trunk Agility

Unlike African elephants, which rarely use their forefeet for anything other than digging or scraping soil, Asian elephants are more agile at using their feet together with the trunk to manipulate objects.

Aggressive Behavior

They can sometimes exhibit violent behavior.

Vocalization Types

Asian elephants produce three basic sounds: growls, squeaks, and snorts. Basic growls are used for short-distance communication.

Growl Variations

During mild arousal, growls resonate in the trunk and become rumbles; for long-distance communication, growls escalate into roars. Low-frequency growls are infrasonic and produced in many contexts.

Squeak Variations

Squeaks have two forms: chirpings and trumpets. Chirping consists of multiple short squeaks and signals conflict and nervousness. Trumpets are lengthened, louder squeaks produced during extreme arousal.

Snort and Boom Displays

Snorts signal changes in activity, and increase in loudness during mild or strong arousal. When an elephant bounces the tip of its trunk during strong arousal, it creates booms that serve as threat displays.

Auditory Capabilities

Elephants can distinguish low-amplitude sounds.

Tiger Predation on Calves

Rarely, tigers have been recorded attacking and killing calves, especially when calves become separated from their mothers, stranded from their herd, or orphaned.

Adult Predation Vulnerability

Adult Asian elephants are largely invulnerable to natural predation. There is a single anecdotal report of a mother Asian elephant allegedly being killed alongside her calf, but this account is contested.

Recorded Adult Elephant Predation

In 2011 and 2014, two instances of tigers successfully killing adult Asian elephants were recorded: one by a single tiger in Jim Corbett National Park that killed a 20-year-old young adult cow, and another that killed a 28-year-old sick adult bull in Kaziranga National Park further east, which was taken down and eaten by several tigers hunting cooperatively.

Predator Growl Recognition

Asian elephants can distinguish between the growls of larger predators like tigers and smaller predators like leopards; they react to leopards with less fear and more aggression.

Reproductive Pheromone Use

Reproduction in Asian elephants relies on the production and perception of signaling compounds called pheromones, which are transmitted through various bodily fluids. Pheromones are commonly released in urine, and in males they are also found in special secretions from the temporal glands.

Pheromone Function

Once these signals are integrated and perceived, they give the receiver information about the reproductive status of the sender. If both individuals are ready to breed, ritual reproductive behavior occurs and sexual reproduction proceeds.

Male Breeding Competition

Bulls will fight one another to gain access to estrus cows, but strong fights over access to females are extremely rare. Bulls reach sexual maturity around 12 to 15 years of age.

Musth Physiology

Between 10 and 20 years old, bulls experience an annual phenomenon called "musth", a period where testosterone levels are up to 100 times higher than during non-musth periods, and bulls become aggressive. During musth, pheromone-containing secretions are produced by the paired temporal glands located on the head between the lateral edge of the eye and the base of the ear.

Frontalin Role in Musth

The aggressive behaviors seen during musth are linked to varying amounts of frontalin (1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane) throughout the maturation process of bulls. Frontalin is a pheromone first isolated in bark beetles, but it is also produced by bulls of both Asian and African elephants.

Frontalin Secretion and Function

The compound can be excreted through urine as well as the bull’s temporal glands to enable reproductive signaling. During musth, increased concentrations of frontalin in a bull’s urine communicate his reproductive status to female elephants.

Female Estrous Cycle

Like other mammals, hormone secretion in female elephants is regulated by an estrous cycle. This cycle is regulated by surges in Luteinizing hormone that occur every three weeks, an estrous cycle pattern also seen in African elephants that is not known to occur in other mammals.

Ovulation and Mating Cues

The first Luteinizing hormone surge is not followed by ovulation (egg release from the ovaries), but some female elephants still display expected mating behaviors during this surge. Female elephants give ovulatory cues using sex pheromones.

Female Sex Pheromone

A main component of these cues, (Z)-7-dodecen-1-yl acetate, is also a sex pheromone in numerous insect species. In both insects and elephants, this chemical compound acts as an attractant to assist the mating process.

Pheromone Detection

In elephants, the chemical is secreted through urination, which helps attract bulls for mating. Once detected, the chemical stimulates the bull’s vomeronasal organ, providing information about the female’s maturity.

Reproductive Signal Processing

Reproductive signaling between male and female elephants is transmitted through olfactory cues in bodily fluids. In males, increased frontalin levels during musth heighten their sensitivity to the (Z)-7-dodecen-1-yl acetate produced by female elephants.

Flehmen Response

Once the chemical is perceived by receptors in the trunk, a sequence of ritualized behaviors follows. Male responses vary based on both the stage of development and the temperament of the elephant. This process of receiving and processing signals through the trunk is called flehmen.

Male Breeding Response Cues

Differences in body movement give cues to indicate whether a male is interested in breeding with the female that produced the secretion. A bull ready to breed will move closer to the urine, and an erection response sometimes occurs. A bull not ready to breed will act timidly and try to move away from the signal.

Same-Sex Chemosensory Interactions

In addition to reproductive communication, chemosensory signaling is used to facilitate same-sex interactions. When less developed males detect pheromones from a male in musth, they often retreat to avoid contact with aggressive behavior.

Female Same-Sex Pheromone Use

Female elephants have also been observed communicating with each other through pheromones in urine. The purpose of this same-sex communication is still being investigated, but clear differences exist in signaling strength and receiver response across different stages of the estrous cycle.

Gestation Period

The gestation period for Asian elephants is 18 to 22 months, and cows usually give birth to one calf, with twins occurring only occasionally. The calf is fully developed by the 19th month, but remains in the womb to grow so that it can reach its mother to feed.

Calf Development and Weaning

At birth, a calf weighs around 100 kg (220 lb), and is suckled for up to three years. After a female gives birth, she usually does not breed again until the first calf is weaned, resulting in a four to five-year birth interval.

Mother-Calf Communication

During this period, communication between mother and calf primarily occurs through temporal means. Male calves have been recorded developing sex pheromone-producing organs at a young age.

Calf Sensory Development

Early maturity of the vomeronasal organ allows immature elephants to produce and receive pheromones. It is unlikely that integration of these pheromones produces a flehmen response in calves.

Dispersal and Sexual Maturity

Female calves stay with the herd, while mature males are chased away. Female Asian elephants reach sexual maturity around 10 to 15 years of age and continue growing until they are 30 years old.

Growth and Lifespan

Males reach full maturity after 25 years of age and grow constantly throughout their life. The average life expectancy of an Asian elephant is approximately 60 years. Some individuals have been recorded living into their late 80s. The generation length of the Asian elephant is 22 years.