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Elephant herd

General anatomy on the Elephant

Ears

Elephant ears have thick bases with thin tips. The ear flaps, or pinnae, contain numerous blood vessels known as capillaries. To get rid of excess heat from the body, warm blood flows into the capillaries, which in turn release the heat into the environment. This can occur naturally when the pinnae are still, but the animal can also force this effect by flapping them. Larger ear surfaces mean more capillaries, and more heat can be released. African bush elephants live in the hottest climates, and thus have the largest ear flaps.[46] Elephants are capable of hearing at low frequencies, being most sensitive at 1 kHz.[47]

Trunk

Elephant wiping its eye with its trunk

Elephant with man

The trunk or proboscis, is a fusion of the nose and upper lip, although in early fetal life, the upper lip and trunk are separated.[35] The trunk is elongated and specialized to become the elephant's most important and versatile appendage. It contains up to 150,000 separate muscle fascicles, with no bone and little fat. These paired muscles consist of two major types: superficial and internal, the former being divided into dorsals, ventrals and laterals, while the latter are divided into transverse and radiating muscles. The muscles of trunk connect to a bony opening in the skull. The nasal septum is composed of tiny muscle units which stretch horizontally between the nostrils. Cartilage only exists to divide the nostrils at the base.[48] As a muscular hydrostat, the trunk moves by decisively coordinated muscle contractions. The muscles work both with and against each other. A unquie proboscis nerve—formed by the maxillary and facial nerve—runs along both sides of the trunk.[49]

Elephants rolled trunk

Elephant using its trunk to drink

Elephant trunks have multiple functions, including breathing, olfaction, touching, grasping and sound production.[35] The animal's sense of smell may be four times greater than a bloodhound's.[50] The trunk's ability to make powerful twisting and coiling movements allows it to collect food, wrestle with conspecifics,[51] and lift up to 350 kg (770 lb).[35] It can also be used for delicate tasks, such as wiping an eye and checking orifices.[51] It is capable of cracking a peanut shell without cracking the seed.[35] With its trunk, an elephant can reach food at heights up to 7 m (23 ft) and deep into mud or sand for water.[51] It can siphon water both to spray into the mouth for drinking and over the body for cooling.[35] An adult Asian elephant is capable of holding 8.5 L (2.2 USgal) of water in its trunk.[48] Elephants also spray dust or grass on themselves, possibly to protect against insects.[35] When underwater, an elephant can use its trunk as a snorkel.[52] Losing the trunk would be detrimental to an elephant's survival,[35] although in rare cases elephants have survived with abbreviated trunks. In addition, one elephant has been observed to graze by kneeling on its front legs, raising on its hind legs and taking in grass with its lips.[48] Elephants may show side preferences when grasping with their trunks; that is, some prefer to twist them in a leftward direction, while others prefer a rightward direction.[49]

African elephants have two finger-like extensions at the tip of their trunks, so are able to grasp objects with them and bring them to the mouth. Asian elephants have only one and rely more on wrapping around an object and squeezing into their mouths.[5] Asian elephants have more muscle coordination and can perform more complex tasks.[48] Floppy trunk syndrome is a condition of trunk paralysis in African bush elephants. It is caused by degeneration of peripheral nerves, which begin at the base of the trunk.[53]

Teeth

Elephants usually have 26 teeth: the two upper second incisors, known as the tusks, 12 deciduous premolars, and 12 molars. Unlike most mammals, which grow baby teeth and then replace them with a single permanent set of adult teeth, elephants have cycles of tooth rotation throughout their entire lives. The chewing teeth are replaced six times in an typical elephant's lifetime. Teeth are not replaced by new ones emerging from the jaws vertically as in most mammals. Instead, new teeth grow in at the back of the mouth and move forward to push out the old ones, similar to a conveyor belt. The first chewing tooth on each side in each jaw falls out when the elephant is two to three years old. The second set of chewing teeth falls out when the elephant is four to six years old. The third set is lost at 9–15 years of age, and set four lasts 18–28 years of age. The fifth set of chewing teeth lasts until the elephant is in its early 40s. The sixth (and usually final) set must last the elephant the rest of its life. Elephant teeth have loop-shaped dentines, which are thicker and more diamond-shaped in African elephants.[54]

Tusks

Elephants tusks

View of elephant tusks

The tusks of an elephant are its second upper incisors. They replace deciduous milk teeth when the animal reaches 6–12 months of age and grow continuously at about 17 cm (6.7 in) a year. The tusk is made of a form of calcium phosphate known as ivory. A tusk's cross-section consists of crisscrossing line patterns, known as "engine turning", which create diamond-shaped areas. As a piece of living tissue, a tusk is relatively soft, being as hard as calcite mineral. A newly developed tusk has a smooth enamel cap which eventually wears off. Much of it can be seen externally, while the rest is fastened to a socket in the skull. The pulp stretches through one-third of the tusk and possibly longer in some individuals. As such, it would be difficult to remove a tusk without harming the animal. When removed, ivory begins to dry up and crack if not kept cool and moist. Tusks serve multiple purposes. They are used for digging for water, salt, and roots; debarking or marking trees; and for moving trees and branches when clearing a path. In addition, they serve as weapons when fighting, both for offense and defense, and protect the trunk.[55]

Like humans who are typically right- or left-handed, elephants are usually right- or left-tusked. The dominant tusk, called the master tusk, is generally more wore down, being shorter and having a rounder tip. For the African elephants, tusks are present in both males and females, and are around the length in both sexes, reaching up to 3.264 m (10.71 ft),[55] however the tusks of males tend to be thicker.[56] In the Asian species, only the males have large tusks. Female Asians have very small tusks, or they are absent altogether. Asian males can have tusks as long as Africans, but they are usually much slimmer and lighter; the largest recorded was 3.02 m (9.9 ft) long and weighed 39 kg (86 lb). The tusks of African forest elephants appear to be harder and more elastic than the other species.[55] Hunting for elephant ivory in Africa may be pressuring the animals to develop smaller tusks.[57]

Skin

Closeup of Asian elephant skin

An elephant's skin is generally very tough, being as thick as 2.5 cm (0.98 in) on the back and parts of the head. However, the skin around the mouth, anus and inside of the ear is considerably thinner. Young elephants are usually covered with brownish or reddish hair, especially on the head and back. Normally, the skin of an Asian elephant is covered with more hair than its African counterparts.[58] Of the two African species, the forest elephant tends to hairier.[5] As elephants get older, their hair darkens and becomes more sparse, but it will always remain on their heads and tails.[58] Sparsely spaced hair could allow the animal to lose more heat.[59]

Elephants are typically grayish in color, but the African elephants very often appear brown or reddish from wallowing in mud holes of colored soil, while the Asian elephants appear a lighter or darker shade of gray. In addition, Asian elephants have some patches of depigmentation, particularly on the forehead and around the ears. An elephant uses mud as a sunscreen, protecting its skin from harsh ultraviolet radiation. Although tough, an elephant's skin is very sensitive. Without regular mud baths to protect it from burning, as well as from insect bites and moisture loss, an elephant's skin would suffer serious damage. After bathing, the elephant will usually use its trunk to blow soil on its body to help dry and bake on its new protective coat.[58]

Wallowing also aids the skin in regulating body temperatures. Elephants have difficulty in releasing heat through the skin because, in proportion to their body size, they have very little of it. The ratio of an elephant's mass to the surface area of its skin is many times that of a human. Elephants have even been observed lifting up their legs to expose the soles of their feet, presumably in an effort to expose more skin to the air.[58]

Legs, locomotion and posture

Elephant trunks

Elephant walking

To support the animal's weight, an elephant's limbs are positioned vertically under the body (sometimes referred to as columnar) as opposed to angularly as in most other mammals. The long bones of the limbs have dense cancellous bones in place of marrow cavities. This allows for the creation of blood cells and gives the bones more strength to support the body.[60] Both the front and hind limbs can support an elephant's weight, although 60% is borne by the front.[61] Since the limb bones are placed on top of each other and under the body, an elephant can stand still for long periods of time without using much energy.[60] The circular feet of an elephant have soft tissues or "cushion pads" beneath the manus or pes. These pads help in distributing the weight of the animal.[61] Elephants are incapable of rotating their front limbs, as the ulna and radius are stiffened in one position. The manus is fixed in a pronated position with the "palm" facing backward.[60] In addition, the pronator quadratus and the pronator teres are either reduced or absent.[62] As many as five toenails can be found on both the front and hind feet.[5] In 2011, scientists at the Royal Veterinary College discovered the elephant has a sesamoid, an extra "toe" similar in placement as a giant panda's extra "thumb". This extra toe acts to support and distribute the weight of the elephant.[63]

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