Tuesday, 12 June 2012

Sentinels of the Savannah


As we traversed through Ol Pejeta Conservancy, leaving behind herds of elephants, Thomson’s gazelles, troops of olive baboons and a few scattered warthogs, we came across an animal seen only north of the Equator in Kenya – a Somali or reticulated giraffe. What we had seen previously in the wild were Maasai giraffes, found south of the Equator in Kenya and the third kind of Kenyan giraffes, Rothschild are hardly seen in the wild. As the name suggests, a reticulated giraffe can be identified by its netted coat consisting of large chestnut coloured polygon boxes outlined by a network of bright white lines – most distinct pattern of all giraffes. By the way, every giraffe has a unique pattern - much like a human fingerprint. Aptly called “Sentinels of the Savannah” by Helen Roney Sattler (American author of non fiction children's books and young adult books), these mega herbivores (all giraffes, not just reticulated) with their staggering height (and almost half that height is neck) are objects of perpetual bewilderment. Go back a few ages and there were giant life forms roaming all over the planet, but today each peek at enormity leaves us wonder struck.
Reticulated giraffe with its netted coat
So why do the giraffes need the height? The theory about getting food from highest tree branches these days is losing its followers. Most scientists are now tending towards the belief that the giraffes need the necks to win over the maidens. Male giraffes fight for females by "necking". They stand side by side and swing the backs of their heads into each others' ribs and legs. To help with this, their skulls are unusually thick and they have horn-like growths called ossicones on the tops of their heads. Their heads, in short, are battering rams, and are quite capable of breaking their opponents' bones. The giraffes with the tallest and strongest necks come out victorious and hence pass on their genes to future generations.

Well nothing comes free - so what is the cost of this long neck? Because a giraffe's brain is around 2 metres above its heart, the heart has to be big and powerful. In fact, for the blood to reach the brain it has to be pumped at the highest pressure of any animal. Giraffes have a difficult time lowering their massive heads to the ground to drink (they do so by spreading their front legs); and this also leaves them vulnerable to predators. No wonder then that the giraffes avoid lowering their heads. Also they have alternative source of water in the form of leaves they eat, which allow them to go for days without a drink. They have very elastic blood vessels and valves to compensate for the sudden change in blood pressure when they lower their heads to drink. They might pass out were it not for a dense network of fine capillaries (the ‘rete mirabile’ - Latin for 'wonderful net') that cushions their brains against rapid changes in blood pressure.

A baby giraffe gets a feel of his mother's height right at the moment of birth when standing up she drops the baby five feet down – which is not as bad as it sounds since the baby itself is nearly six feet tall at birth! During the first week it will grow almost one inch per day - by which time the flat (against the skull) horns will also pop upright.

To maintain their gigantic bodies, giraffes need to eat continuously throughout the day. A giraffe’s front legs are longer than its rear legs—an extra advantage when stretching for leaves. For those leaves that seem just out of reach, a giraffe bridges the gap with a strong, flexible, grey, seventeen-inch-long tongue that is able to grasp leaves from even the thorniest branches. Giraffes are ruminants (just like cows and other ungulates) with a highly efficient digestive system, even by ruminant standards. This allows them to avoid the heat of the day and find a safe place before beginning digestion.

Since I had seen majority of the giraffes (out of whatever I had seen) in towers (which means herds - English language at its peculiar best!), I assumed them to be highly social animals. But in reality, these groups are very loose with no lasting bonds – giraffes seem to join and leave them at random. At any given time, the herd may consist of all males, all females, a mix of females and young, or a mix of all. Unlike most herds, the giraffe herd of 20 animals has no leader.

When I read about them further, it becomes clear enough – they really do not need to be bonded so tightly in a group. Size is on their side and they are tall enough to be able to see possible predators and other herd members that may be spread out over half a mile (they can even spot a moving person a mile away). This advanced warning, combined with good hearing, good sense of smell, sharp hooves and running speeds of 35 miles per hour (that is about as fast as a good horse), is enough to keep the giraffe relatively predator free. Often other animals, such as wildebeest and ostrich, will herd with giraffes because of their ability to detect danger early.

But then again, it is not always easy to shrug off the predators. In spite of all the defence mechanisms and in spite of the fact that mother giraffe will stay by her young to kick away predators with her powerful legs, the young giraffes (and sometimes solitary unwary adults) are hunted by lions, hyena, leopards, and African wild dogs - often as organised groups. If giraffes had somehow managed to stand up to the wild predators over the centuries, they are proving to be no match for the shrewdest predator of all – man. All over Africa, giraffes are in serious decline. Some 30% may have been lost in the past 10 years alone. Reticulated giraffes seem to have fared especially badly, with a drop in numbers of more than 80% from perhaps 30,000 a decade ago to fewer than 5,000 today. Reticulated giraffes inhabit a volatile area (northern Kenya, Ethiopia and Somalia) characterised by a growing human population, poverty, habitat degradation and drought, regional conflicts, overstretched security forces and a widespread availability of automatic weapons. Giraffes are tempting targets because they yield large amounts of meat, while some pastoral groups value them highly as trophies and for their hides, tail hair (for bracelets) and bone marrow.

Will we let the world’s largest pollinators (they transfer genetic material on their muzzles from the flowers of one tree to those of another) fade away so silently?

References:
http://www.discoverwildlife.com/animals/reticulated-giraffes-last-their-kind
http://www.reticulatedgiraffeproject.net/home.html
http://www.newscientist.com/article/dn19135-zoologger-how-did-the-giraffe-get-its-long-neck.html

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