Bones

• The whole skeleton of the elephant weighs about 16.5% of its total body weight.
• An adult female Asian elephant is reported to have 282 bones (Shoshani et al. 1982).
• Weighing on an average 52 kilos, the head, which looks dimensionally massive, is not as heavy as it appears because of the large number of sinuses present. It is made up of 51 bones, all aerated by sinuses (Van-der-Merve et al. 1995).
• The vertebral column is made of 61 bones and the longest rib may reach 96.5 cm in length.
• The cervical bone is very short in the elephant. This is why an elephant cannot turn its neck and look backwards and this makes the elephant nervous about anything approaching from behind.
• The almost vertical limbs enable them to stand for long periods of time, as well as support the enormous body weight. The bones are arranged in direct line with one another, like a pillar providing rigid support for the enormous body. But the vertical nature of the foot does not allow the elephants to jump, but they can hop and leap. They can also walk forward and backward on very narrow stretches of land.
• The thigh bone is the largest bone in the body. An adult animal has a 114.3-cm long femur (thigh bone).

Trunk

• Trunk is the modified upper lip.
• It is used to drink, dress the food as well as used as a snorkel. The trunk also grasps the food and conveys it to the mouth for mastication. Since the tongue cannot be protruded, the dextrous trunk places the food on the tongue.
• The trunk also acts as an olfactory organ, which is a well-developed means of communication in elephants. It is used to test different smells by touching the object and placing the tip inside the mouth.
• The trunk is also used in threatening gestures and play fighting. During mock charges, it stretches its trunk outward, but if it holds its trunk tucked down, it is a real charge.
• With the trunk, an elephant-calf can lift about 4.5% of its bodyweight while an adult elephant can lift around 270 kg.

Digestion and defecation

• The elephant is a non-ruminant mega herbivore and its digestive system is compared to that of a horse or a zebra.
• Elephants while grazing, pull out grass from the ground, remove the dust and mud by beating on the forelimb, and then eat the dressed food. They spend considerable time dressing palm fronds. The animal eats only the inner portion.
• Healthy elephants thoroughly masticate edible portions of the food.
• The maximum capacity of the stomach in an adult female elephant was found to be 76.6 litres (Shoshani 1982). In herbivores many of the complex carbohydrates that cannot be digested by the mammalian enzymes are digested by fermentation with the help of symbiotic microbes present in the anterior or posterior portions of the gastrointestinal tract. Anaerobic microbes inhabit the caecum and colon of elephants, similar to those seen in the rumen and reticulum of ruminants. The highly specialised anaerobic bacteria act on fragmented particles of cellulose, chromatophores and other partially degraded substances digesting these plant materials. Volatile fatty acids (VFA) is a major source of energy for elephants as in other herbivores, but the proportion of propionic acid is less. Probably this is compensated by absorption of carbohydrates from the foregut. Hence, the proportion of soluble carbohydrates available for fermentation in the caecum is much less than that of rumen in cattle.
• On an average, elephants excreted 3.9-kg faeces per 100 kg of body mass a day. Elephants defecate 14-18 times in a day passing 5-6 boluses of 1-1.5 kg, each time.
• Elephants void urine 10-14 times a day. Volume discharged at one time varies from 5-11 litres with a total 24-hour discharge of about 50 litres (Benedict Sikes 71, Wallach Boever 83).
• Elephants use the digestive strategy of passing large amounts of low quality forage through their gut within a short period of time (Loehlein et al. 2001). The passage time of food materials through the gastrointestinal tract ranges from 18 to 24 hours.

Teeth

• Elephants have six sets of molars in their lifetime.
• A total of four teeth are present at a time, two in the lower and upper jaw respectively.
• If two teeth are seen at a time in the same alveolar pocket, the anterior one is the worn out old tooth and the posterior is the new tooth. This movement of teeth is unique to elephants, as in other animals the milk teeth are shed when the permanent teeth erupt.
• The last (sixth) set of teeth appears at the age of around 40 years and is almost worn out by the age of 60. Old elephants with their worn out tooth often confine themselves to an area where succulent food to the tune of 200-250 kg and water to an extent of 125-150 litres are available daily, until their probable death due to starvation. Hence in the wild, elephants that feed exclusively on fibrous food, the longevity is almost limited to 60 plus.
• In captivity, when high calorie, easily digestible, soft foods are given, elephants may live up to 70 years or even more.

Tusks

• Tusks are lateral incisors that grow continuously throughout the animal’s lifetime. They emerge on the sides of the base of the trunk. Almost half of the tusk from its base is hollow with tusk pulp inside. It is made up of dentine and the surface is covered with shiny white enamel. The tusks are used for digging, carrying loads, debarking trees, in combat as well as in behavioural display.
• Asian elephant females do not have tusks but have a very small growth known as tushes, which are usually harder than the tusks.
• Some male Asian elephants also do not have tusks and are known as makhnas.
• External appearance of tusks varies with almost all elephants.
• They grow at an average of 15-20 cm in length each year.

Brain

Elephants possess the largest brain among land mammals (Cozzi et al. 2001), four times the size of a human brain.

Ear

• The elephant ear is very large and peculiar in shape.
• Ears are used for auditory purposes, balancing the body, thermoregulation and for signalling.
• Elephants have difficulty in losing excess body heat through the skin surface. An elephant’s ear will shed almost 100% of the total heat when maximally vasodilated and flapped gently.
• Since the size and shape of the ear is different in different elephants it is used in identification.
• Whenever an elephant perceives threat, it opens its ears wide.
• The fold on the dorsal aspect of the ear is an indication of the age of elephant.
• Elephants cannot hear above 10.5 kHz at an intensity level of 60 dB, but can hear low frequency sounds.
• Elephants communicate by producing deep growling or rumbling noises. When alarmed they let out an ear splitting trumpet.

Body surface

• Irregular surface of the elephant’s body cools it better than a smooth surface as the irregular surface retains more water.
• Elephants take dust-baths even after spending a great deal of time in the water. Apart from cooling the body, dust baths protect the elephants from insects and radiation (Rees 2002).

Eyes

• Eyes in elephants are 1.5-2 inches long and 1 inch wide.
• The area of vision is limited to only up to 30-50 metres because of the position of the eyeball, presence of trunk and ear as well as the short neck. When the elephant senses trouble, it moves its body alternatively from side to side in order to see behind, instead of walking straight ahead. But this is compensated by extremely well developed olfactory and auditory capacities.

Skin

• Pachyderm, derived from the Greek word Pachydermose (thick skinned).
• The skin of an elephant is as thick as 2.5-4 cm on the head and back.
• The colour of the skin is greyish black.
• De-pigmentation is noticed on the fore head, upper portion of the trunk and the ears.
• Although the skin is dry due to the absence of sweat gland, it is soft and supple.
• The highly wrinkled skin helps absorb water and helps retain surface moisture to compensate for evaporative heat loss. This is highly useful during periods of drought.

Communication

• Chemical communication relates to signalling between opposite sexes for mating. Secretions at the base of the toes, temporal gland and urogenital tract as well as saliva and mucus lining of the trunk produce chemical signals. Olfactory communication is achieved by pheromones. Urine of a cow elephant in oestrus produce pheromones to attract bulls, while the strong smell of the temporal gland secretion advertises musth in bulls.
• Tactile communication happens through sight and touch. When elephants meet, they vocalise, rub their bodies, press each other’s foreheads, intertwine trunks or put trunks in each other's mouths. These tactile contacts reinforce their bonds.
• Acoustic communication happens both in the audible and inaudible (subsonic) range. Extensive studies have confirmed that elephants produce low frequency sounds to interact in thick vegetation and among separated groups. In nature, infrasonic sounds are produced by ocean waves, volcanoes, earthquakes, thunderstorms, whales, etc. Elephants are the first terrestrial mammals reported to produce infrasound. The intensity of sounds produced is strongest at 18 hertz compared to 100 Hz in humans and 2500 Hz in mice. Infrasonic calls produced by elephants can travel 1-5 km or even more.
• Seismic waves in the ground are also used for communication.

Musth

• The word musth is derived from the Hindi or Persian word ‘mast’ meaning intoxicated or angry.
• It is a physiological phenomenon seen in all adult healthy male elephants, usually every year, when the elephant shows aggressive behaviour and secretion is seen from the swollen temporal gland.
• Some of the other signs seen during this time are unusual alertness, spreading of ears, staring eyes with roving eyeballs, stiff and tense body, extended blowing of trunk and unusual vocalisation.
• Musth bulls are extremely dominant and try to keep the non-musth males away from the females.
• In many cases, successful mating in the wild happens in a bull in musth or one that is about to enter the musth period.
• The duration of musth may vary between 3-80 days.