Elephant Museum - Part 2

External biology -continued

Head and neck

An elephant's skull needs to be physically large in order to support the heavy tusks and powerful trunk To minimize weight, the huge skull has a thick wall but contains large honey-comb like spaces. Male African elephants have a curved forehead. Females are more square in profile. Elephants have short necks and cannot turn their heads completely sideways. Legs

The leg bones are placed vertically above each other forming a rigid column when at rest. This helps to support the animal's enormous weight without the risk of its legs buckling but means elephants are unable to run or jump. Their normal walking rate is 6-8 km/h. The whole mass of the huge head, the trunk and the tusks, is carried by the forelimbs. This image shows how weight is distributed across the animal. Skin The skin thickness varies from paper thin on the inside of the ears, around the mouth and anus to about 2.5cm on the back and parts of the head.

Wallowing protects against ultraviolet radiation, parasites and moisture loss. Scratching and bathing are also important behaviours in skin care. The skin colour is usually gray although often seems brown or reddish from wallowing in mud holes. Feet

Elephants walk on tip-toe. The animal's weight rests on the tip of each toe and on a fibrous 'cushion' of fatty and connective tissues which acts as a shock absorber. This material absorbs sound, enabling these massive creatures to walk almost silently.

The front feet are larger and more rounded than the hind feet, which are smaller and oval.

The surface of the foot is very flexible and sensitive, adapting naturally to any irregularities of terrain. The soles of the feet are very thick, horny and superficially cracked. Trackers can use these unique 'footprint' markings to help identify individual animals.

Tusks

Elephant tusks are upper incisor teeth which grow very long. They are similar to human teeth, consisting of a central core of pulp which is covered in dentine and encased in bone-like cementum. The internal dentine, making up 95% of the tusk, is the substance commonly referred to as 'ivory'.

It is a combination of mineral-based connective tissue and collagen proteins, making it very strong. Young elephants also have a layer of enamel at the very tip of their tusks but this is soon worn off and not replaced.

Tusks grow throughout an elephant's life although they may wear down or even break due to extensive use or major clashes. Many elephants favour one tusk over the other (effectively they are left- or right- tusked just as you are left- or right-handed). The most-used, or ‘master' tusk is usually shorter than the ‘servant' as it is worn-down by regular use. Often the most gentle bull elephants have the largest tusks in a population, as they are less likely to break them in a fierce clash.

About one quarter of the tusk is housed within the elephant's skull, which has developed in order to be able to bear the weight of these huge teeth.

Toes

The forefeet have 4 or 5 toes, while the hind feet have 3-5. The toenails are made of the same substance found in human toenails (keratin) and are attached to the skin.

Eyes

Elephant eyes are almost identical in size to those of a human. They are normally green or hazel in colour and are protected by long eyelashes. Elephants do not have tear ducts. In bright sunlight, elephants have poor eyesight. They can see best in dim light.

Trunk

An elephant's trunk is extremely versatile. 70% of the air that elephants breathe is inhaled through the trunk. Like our noses, it can smell the surrounding environment. It can be used to touch and feel objects and other elephants. It can create trumpeting sounds and give physical communication signals. It can be used to break branches from trees, pluck bundles of grass, and suck up and spray water or dust over the body or into the mouth.

Trunks can be over 1.5m long and weigh more than 150 kg. They contain eight major muscles but have 150,000 fascicles (or portions of muscles) which provide amazing dexterity and strength. A trunk can lift more than 250 kg in weight and hold over 8 litres of water.

African Elephants have two prehensile 'fingers' at the end of the trunk which enable them to grasp objects.

Ears

An African elephant's impressive ears are not just used for hearing. They help regulate the animal's body temperature and may also be spread out wide in threat displays. Elephant ears contain a large number of blood vessels which are covered by very thin skin. When the ears are flapped, air flows over the blood vessels and the animal loses heat from them. Measuring up to 2m high and over 1m wide, 12 litres of blood can flow through each ear every minute and the animal's body temperature can be reduced by three degrees. An elephant's average body temperature is 35.9 degrees Celsius, just below that of a human (37 degrees). Elephants have excellent hearing and are thought to be able to communicate with other individuals several kilometres away. They can hear very low frequency sounds (their hearing range is 1-20,000Hz) which are not audible to humans (who have a hearing range of 20-20,000Hz).

The distinctive tears and nicks in elephants' ears are used by scientists to help identify individual animals in the wild.

Tail An elephant's tail can be up to 1.5 m long. It is used to swat flies away.

Adult elephants may grab a young animal's tail with its trunk in order to guide it. Older calves may also sometimes hold their mothers' tails as they walk.

Information supplied by: http://www.sanparks.org/parks/kruger/elephants/default.php