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Camels can survive for days in deserts with little food and no water due to their unique physiology. Contrary to the common belief, a camel does not store water in its stomach or its hump. Instead the hump stores fat which serves as a reserve for energy and a source of water when in need. When the fat is utilized by the camel’s body, hydrogen is released which combines with oxygen to form water. Camels also use water from other body tissues in a similar way. As body tissues dehydrate, it can lose as much as 25 per cent of its body weight without suffering any permanent damage. But when it does find water, a thirsty camel may drink up to 150 litres in 15 minutes. The water passes rapidly into its body tissues, making the animal fit for another desert crossing.

Electricity in fish is generated by the normal functions of nerves and muscles together with a chemical reaction. The electricity is produced in modified muscle tissue called electric organs. The nerves from these organs are joined to the brain. The electricity is produced by the passage of a stimulus along a nerve and a contraction in a muscle. The discharge goes from the belly to the back. It is a defensive mechanism in most cases, but is also used to kill the prey. Fishes are immune to their own shocks because of the insulating layers of fat.

Bats navigate by making use of sounds that they emit. The way these sounds bounce off from nearby objects and obstacles and return to the bats’ ears enables it to gauge distances and avoid obstacles. Being in the range of 100,000 Hertz, these sounds are inaudible to human ears which can hear only upto 20,000 Hertz. Bats can discriminate between faint echoes of their own sound in the presence of other sounds.

Interestingly, large bats such as the flying fox do not use sound for navigating but rely on vision instead. They fly and feed by day and become disoriented if forced to fly in the dark.

It is not quite correct to say that a chameleon can change its colour to match coloured surroundings. A chameleon merely lightens or darkens its body colour in response to changes in the surrounding temperature and brightness. Its colour darkens in dim, cool surroundings and lightens when conditions are reversed. Chameleons also show lightened body colour if suddenly frightened or excited in which case the body colour may not blend with the environment.

The quick-change ability of the chameleon is due to the pigment containing cells located just under the skin surface. When the pigments in the cells are concentrated at the centre, the skin is light in colour. When the pigments disperse throughout the cells, the skin colour darkens. This ability to change colour possibly helps the chameleon to regulate body temperature as well as to camouflage themselves as a protective measure.

All dogs have keenly developed senses of smell and hearing. Dogs naturally depend on their sense of smell to identify friends and foes. They also mark off their territory with their own urine which is individually recognizable to themselves and other dogs. Human beings also have individual ‘smells’ although they are usually unable to identify it. Each individual has a unique odour -the product of diet and subtle differences in metabolism.

Dogs can ‘read’ these individual odour signatures and distinguish between different individuals and follow the scent-trail for long distances even in the absence of other clues.

Breeds such as the Blood hound, German shepherd and Beagle are famous for their tracking skills. 

Many methods, not all fail-safe seem to be used by the animals in identifying their young. Some animals lick their babies at birth, anointing them with a chemical tag they can identify. Others rely on voice identification with the chicks learning to respond to parental calls. Still others rely on visual identification, with the babies responding to the first large moving object (usually the mother) they see and following it everywhere.

Many animals, especially the social ones, do not discriminate between babies in the herd.