Roger Hanson: A few facts about camels
Climate change has increased the size of the Sahara Desert by 10 per cent in the last 100 years.
This creeping desertification has affected the Masai people of Kenya. Traditionally they relied on cattle to supply their needs but climate change has meant that 30 per cent of their livestock now comprise a mammal far better adapted to deal with dry conditions – the camel.
The ancestry of camels can be traced to North America where about 45 million years ago the earliest known camel, Protylopus, lived.
Five million years ago the direct descendant of modern camels, Procamelus, crossed the Bering land bridge from North America into Asia, thrived and continued evolving.
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Modern camels were domesticated about 3,000BC in southern Arabia. Today there are three surviving species of camel, the single-humped dromedary or Arabian camel, the two-humped Bactrian camel of Central Asia and the endangered Wild Bactrian camel found only in NW China and Mongolia.
Bactrian camels can weigh up to a tonne and dromedaries weigh up to 600kgs. Male dromedaries have an inflatable pink sac, visible only during the mating season when it hangs from the side of its mouth. Called a "dulaa", it is a palate and its purpose is to warn off other males and attract females.
A common myth is that camels store water in their humps. The hump is a reservoir of fatty tissue and concentrates fat in one location ensuring that the camel minimizes the amount of fat that is distributed across its body – layers of insulating body fat are unwanted in hot desert conditions.
Camels can go for 10 days without any water and for months if they can find green plants. Camels don't store much more water than other similarly-sized mammals, the key to their desert survival is that they are superbly adapted to minimizing water loss. They lose only 1.3 litres of water per day whereas cattle can lose 30 litres a day.
A camel has the obvious adaptations to desert conditions: long legs to keep its body away from the hot ground and two-toed feet which have been described as resembling tyres filled with fat. The undersides of its feet are leathery, enabling its feet to splay, preventing it from sinking in the soft sand.
In the summer a camel's coat becomes lighter in colour to reflect the desert sun. Camels have long eyelashes and ear hair which, along with closable nostrils, keeps the sand at bay in windy conditions. They have a "nictitating membrane" that can be drawn across the eye to protect and moisten it.
When a camel exhales, the water vapour is trapped by its nostrils and reabsorbed into the body. Dromedaries have a thick pad of tissue over their sternum, called a pedestal, which, when they are sitting, leaves a gap between the hot ground and their bodies allowing them to keep cool.
The gestation period of camels is 14 months. They have a life expectancy of about 50 years and they can run up to 65kms/hr.
Camels have some less obvious adaptations. The red blood vessels of a camel are oval, not circular. This allows the blood to flow more easily even during extreme dehydration and also prevents rupturing of cells when dehydration produces high concentration differences in the body.
Camels have a complex of arteries and veins close to each other called the rete mirabile or "wonderful net", that cools blood flowing to the camel's brain, preventing it from overheating.
The kidney and intestines of a camel have adaptations that enable it to conserve water and limit the volume of urine. A camel's urine is a thick syrup and its faeces are so dry that they can be used immediately to fuel fires.
In the 1860s camels were exported to Australia since they were the only means by which supplies could be transported into the Outback by early explorers.
Today Australia is home to more than one million feral dromedary camels which have become a pest because they drain water sources vital to native wildlife.
In many parts of the world however, as the Masai in Kenya are showing, camels, far from being a pest, are becoming the new cattle in countries most affected by climate change.
- Taranaki Daily News