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unlike most mammals, which grow baby teeth and then replace them with a permanent set of adult teeth, elephants have cycles of tooth rotation throughout their entire life. the tusks have milk precursors, which fall out quickly and the adult tusks are in place by one year of age, but the chewing teeth are replaced five[35] or ,very rarely, six[36] times in an elephant's lifetime.
only four chewing teeth (pre-molars and/or molars), one on each side of each jaw, are in primary use at any given time. adult teeth do not replace milk teeth by emerging from the jaws vertically as human teeth do. instead, new teeth grow in at the back of the mouth, pushing older teeth toward the front. in african elephants, the first two sets of chewing teeth (pre-molars) are in place when an elephant is born. the first chewing tooth on each side in each jaw falls out when the elephant is about two years old. the second set of chewing teeth falls out when the elephant is about six years old. the third set is lost at 13 to 15 years of age, and set four lasts to 28 years of age. the fifth set of chewing teeth (molars) lasts until the elephant is about 43. the sixth (and usually final) set must last the elephant the rest of its life. when an elephant becomes more than 60 years old, the last set of molars is worn to stumps, and it can no longer feed properly and eventually dies. moss reports an observation of an elephant in her sixties whose molars were worn smooth and about one-quarter of their original size who survived "with extra chewing and longer feeding bouts." abcesses of chewing teeth, as well as of tusks and jaws, are common in elephants, and may lead to premature death.[37]
were it not for their teeth wearing out, their metabolism would allow them to live for much longer. however, as more habitat is destroyed, the elephants' living space becomes smaller and smaller; the elderly no longer have the opportunity to roam in search of more appropriate food and will, consequently, die of starvation at an earlier age.[citation needed]
tusks in the lower jaw are also second incisors. these grew out large in deinotherium and some mastodons, but in modern elephants they disappear early without erupting.
skin
skin of an african (left) and asian (right) elephant.
african elephant bathing
elephants are colloquially called pachyderms (from their original scientific classification), which means thick-skinned animals. an elephant's skin is extremely tough around most parts of its body and measures about 2.5 centimetres (1.0 in) thick. however, the skin around the mouth and inside of the ear is paper-thin. normally, the skin of an asian is covered with more hair than its african counterpart. this is most noticeable in the young. asian calves are usually covered with a thick coat of brownish red fuzz. as they get older, this hair darkens and becomes more sparse, but it will always remain on their heads and tails.
the species of elephants are typically greyish in colour, but the africans very often appear brown or reddish from wallowing in mud holes of coloured soil. wallowing is an important behaviour in elephant society. not only is it important for socialization, but the mud acts as a sunscreen, protecting their 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 earth on its body to help dry and bake on its new protective coat. as elephants are limited to smaller and smaller areas, there is less water available, and local herds will often come too close over the right to use these limited resources.
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. since wild elephants live in very hot climates, they must have other means of getting rid of excess heat.
legs and feet
elephant using its feet to crush a watermelon before eating it.
an elephant's legs are great straight pillars, as they must be to support its bulk. the elephant needs less muscular power to stand because of its straight legs and large pad-like feet. for this reason an elephant can stand for very long periods of time without tiring. in fact, african elephants rarely lie down unless they are sick or wounded. indian elephants, in contrast, lie down frequently.
the feet of an elephant are nearly round. african elephants have three nails on each hind foot, and four on each front foot. indian elephants have four nails on each hind foot and five on each front foot. beneath the bones of the foot is a tough, gelatinous material that acts as a cushion or shock absorber. under the elephant's weight the foot swells, but it gets smaller when the weight is removed. an elephant can sink deep into mud, but can pull its legs out readily because its feet become smaller when they are lifted.[citation needed]
elephants swim well, but cannot trot, jump, or gallop. they do have two gaits: a walk and a faster gait that is similar to running.
in walking, the legs act as pendulums, with the hips and shoulders rising and falling while the foot is planted on the ground. with no "aerial phase", the faster gait does not meet all the criteria of running, as elephants always have at least one foot on the ground. however, an elephant moving fast uses its legs much like a running animal, with the hips and shoulders falling and then rising while the feet are on the ground. in this gait, an elephant will have three feet off the ground at one time. as both of the hind feet and both of the front feet are off the ground at the same time, this gait has been likened to the hind legs and the front legs taking turns running.[38] tests at the thai elephant conservation centre are reported to show that fast-moving elephants 'run' with their front legs, but 'walk' with their hind legs.[39]
although they start this "run" at only 8 km/h,[40] elephants have been reported to reach speeds up to 40 km/h (25 mph),[41] all the while using the same gait. in tests at the thai elephant conservation centre the fastest elephants reached a top speed of 18 km/h (11 mph).[39] at this speed, most other four-legged creatures are well into a gallop, even accounting for leg length. spring-like kinetics could explain the difference between the motion of elephants and other animals.[42]
ears
difference between asian (left) and african (right) elephant ears.
the large flapping ears of an elephant are also very important for temperature regulation. elephant ears are made of a very thin layer of skin stretched over cartilage and a rich network of blood vessels. on hot days, elephants will flap their ears constantly, creating a slight breeze. this breeze cools the surface blood vessels, and then the cooler blood gets circulated to the rest of the animal's body. the hot blood entering the ears can be cooled as much as ten degrees fahrenheit before returning to the body. differences in the ear sizes of african and asian elephants can be explained, in part, by their geographical distribution. africans originated and stayed near the equator, where it is warmer. therefore, they have bigger ears. asians live farther north, in slightly cooler climates, and thus have smaller ears.
the ears are also used in certain displays of aggression and during the males' mating period. if an elephant wants to intimidate a predator or rival, it will spread its ears out wide to make itself look more massive and imposing. during the breeding season, males give off an odour from the musth gland located behind their eyes. joyce poole, a well-known elephant researcher, has theorized that the males will fan their ears in an effort to help propel this "elephant cologne" great distances.[43]
biology and behavior
