Elephant anatomy: trunk, tusks, ears, teeth, skin and feet

The trunk

The trunk is a fusion of the nose and upper lip. It contains no bones; cartilage is found only at its base, where it divides the nostrils. Instead it is made of muscle, blood and lymph vessels, nerves, connective tissue and skin. San Diego Zoo Wildlife Alliance describes eight major muscles on each side and about 150,000 muscle fascicles in total, arranged so that they can work against each other and move the trunk in any direction.

That arrangement makes the trunk both strong and precise. It can lift heavy logs and also pick up a single piece of straw. Elephants use it to breathe, smell, eat, drink, spray water and dust over themselves, snorkel while swimming, greet and caress other elephants, and make sounds. To drink, an elephant draws water part way up the trunk, curls it to the mouth and pours it in; the Smithsonian says an Asian elephant's trunk holds about 7.5 liters. The tip differs between species: African elephants have two finger like projections and Asian elephants one.

Tusks and ivory

Tusks are modified upper incisor teeth, the only incisors an elephant has. They are made mostly of dentine (ivory) with a cap of enamel that wears away, and they contain a pulp cavity with nerve tissue. About one third of a tusk sits inside the skull. Calves have small milk tusks that fall out at about a year old; permanent tusks appear beyond the lip at two to three years and keep growing throughout life.

Elephants use tusks to dig for water, salt and roots, strip bark, lever and move objects, defend themselves and display to rivals, and even to rest the trunk on. Like people who are left or right handed, elephants tend to favor one tusk, which is usually more worn. In both African species, males and females usually have tusks; in Asian elephants, usually only males grow large tusks, and females have small tushes. Ivory demand drives poaching, which is covered on the conservation page.

Teeth: six sets of molars

An elephant usually has four working molars at a time, one on each side of the upper and lower jaw. Each can be the size of a brick and weigh about 2.3 kg. Instead of erupting from below, new molars grow in from the back of the jaw and push the worn ones forward until they break off and fall out or are swallowed. An elephant goes through up to six sets in its life, each larger than the last, and scientists can estimate an elephant's age from which molars it has and how worn they are.

When the last set wears down, very old elephants struggle to chew tough plants and may stay near swamps with soft vegetation. San Diego Zoo Wildlife Alliance notes that this habit is probably the origin of the myth of elephant "graveyards."

Ears that work like radiators

Elephant ears are thin and packed with blood vessels. When an elephant flaps its ears, blood flowing through them cools down before returning to the body; the Smithsonian says this can lower body temperature by several degrees. African elephants, which often live in hotter, more open habitats, have much larger ears than Asian elephants. Ears are also used in communication: spreading them wide makes an elephant look bigger. Read more in why elephants have such big ears.

Skin: thick but sensitive

Elephant skin can be about 2.5 cm thick on parts of the back yet paper thin inside the ears. Despite its thickness it is very sensitive, with a rich nerve supply; San Diego Zoo Wildlife Alliance says an elephant can feel a fly land on it. The deep wrinkles, especially in African elephants, trap moisture that evaporates slowly and helps cooling. Elephants protect their skin from sun and insects by spraying themselves with water and coating themselves in mud, sand or dust. Calves are born quite hairy and lose much of that hair with age.

Legs and feet

An elephant's legs are stacked almost vertically under the body like pillars, which supports enormous weight and lets the animal stand for long periods with little effort; elephants can even sleep standing up. The Smithsonian notes that elephant long bones lack the open marrow cavity of most mammals and are instead filled with dense, spongy bone, making them stronger. Elephants actually walk on their toes, which rest on a thick, fibrous pad that acts as a shock absorber with every step.

Brain

The elephant brain weighs about 4 to 6 kg, the largest of any land animal. A 2014 study led by Suzana Herculano-Houzel counted about 257 billion neurons in an African elephant brain, roughly three times as many as a human, but found that about 98% of them sit in the cerebellum, which is involved in movement and coordination, including fine control of the trunk. What elephants do with that brain is covered on the intelligence page.