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Published on July 14th, 2011 | by Yellow Magpie0
The Giraffe: A Peculiar Giant
A small simian rests itself in a thick tree, secure in the knowledge that it is safe. A noise startles it but it remains confident in its choice of location. A rapidly-moving, snake-like appendage pierces through the green and the terrified monkey scuttles away.
It is the tongue of a giraffe, one of the only animals with the capabilities to reach such an awkward spot.
Giraffes’ bio-mechanical systems are incredibly adapted, perhaps too specialised. They, courtesy of natural selection, have evolved ingenious solutions to some very tricky problems posed by their unusual bodies.
It’s All In The Neck
There are two accepted reasons why giraffes have such long necks. Originally, it was thought that their necks gave them the ability to access areas that other animals could not in order to obtain food. Recently, scientists have begun to rethink this theory.
Keen observers noted that giraffes spent most of their time eating at heights that were between two and four metres, even though some could comfortably feed at six metres.
Elephants can feed at up to five metres which suggests that giraffes’ exclusivity to higher foliage is a marginal advantage. This led scientists to cast doubts on this theory and look elsewhere for a better answer.
They found a more satisfying explanation in sexual selection. Giraffes often use their heads as weapons, utilising their neck to fling themselves at each other. Long napes are especially important to the males, who fight with one another, vying for the females. The longer limb gives them a heavier head and a greater advantage.
Having long necks became very important and evolution selected animals with these preferred characteristics.
A Nape Design
The neck of a giraffe is designed to be naturally upright. It is held up by tendons. Powerful muscles are needed to enable the giraffe to lower their heads. Because the tension on a lowered neck is quite strong, giraffes can catapult their necks back up – this comes in very handy for males fighting other males (necking).
Despite the length of the giraffe’s nape, they only have seven vertebrae, the exact same number as humans and other mammals.
Giraffes also use their long necks to reach deep inside trees, places that other animals cannot reach.
Preferred Diet And Digestive Efficiency
Giraffes preferred food of choice is the Acacia tree and they get access to the leaves by using their remarkably dexterous tongue. Some tongues can be over 50 centimetres (18 inches) in length. Acacia trees are protected by thorns, it takes a highly sensitive and slender tongue to strip the leaves off the branches. Giraffes spend as much as 12 hours a day feeding on trees.
The key to giraffes ability to obtain energy from food resides in their digestive system which is incredibly efficient. Their thin, long intestines absorbs as much of the nutrients as possible.
The lungs of a giraffe are very different from human lungs. They can inflate and deflate almost instantaneously allowing the animal to take in huge quantities of oxygen as they gallop. Their galloping motion and their digestive system help to push the air out of their lungs when lots of oxygen is demanded.
The length of a giraffe’s neck means other complications need to be overcome. Such large distances require a highly powerful heart. The muscle wall of the side of the heart that pumps blood to the neck is massive, up to ten centimetres in thickness (three inches).
Giraffes are also the animal with the highest blood pressure. This creates a problem which is exacerbated when the animal is running. That of blood pooling out of the blood vessels and away from vital organs such as the brain. Blood pooling can be fatal and results in fighter pilots blacking out.
Giraffes get over this hurdle by having very thick skin which presses against the blood vessels preventing the blood from sweeping out under extreme pressure.
The final problem that such an unusual body with ultra high blood pressure faces is the danger of damaging its organs from a surge in pressure when the animal lowers its head.
Giraffes deal with this by having a network of blood vessels that alleviates the pressure when the head is lowered. Blood is also prevented from flowing back into the brain by a series of valves located in the jugular vein.
The Skeletal System
The unusual body of giraffes requires very clever adaptations. This is especially true of their skeleton. Their bones are very thick and powerful with elongated limbs. These limbs allow them to move at 50 kilometres per hour (30 miles per hour) which is fast enough for them to outrun most predators.
Even very young giraffes are able to move at these speeds. This is because young giraffes are born with very long legs, nearly one and half metres (five feet). Adults have legs that are two metres long (six and a half feet).
A Peculiar Patch
The patches on giraffes serve dual functions. The colours provide the giraffe with camouflage helping to make the animal harder to spot and therefore safer from predators.
The second function has only recently being discovered. The patches act as a cooling mechanism to help the giraffe to lose excessive body heat. Each patch is surrounded by a large blood vessel which fills the patch with a network of smaller blood vessels. The overarching theory behind these patches is that they allow the animal to spend longer periods of time eating. With this cooling system the animal is not thwarted by the hot rays of the Sun.
Giraffes are the paradigm of evolution. Their long limbs meant they have had severe engineering problems to overcome which they have done so successfully. Nonetheless, this is an animal that has become so specialised that its future is quite precarious. It is unlikely that such an animal will be around for long.
- Giraffes can be over five metres (18 feet) high.
- They can weigh 1,900 kilogrammes (4,200 lbs).
- Giraffes usually live up to 20 years but some have been known to live as long as 24 or 25 years.
- They are found in Africa.
Inside Nature’s Giants is a well-shot Channel 4 documentary. From September 2011 a book will be available covering the animals shown in the series.
You can get Inside Nature’s Giants from here.
For people living in Ireland or the United Kingdom, you can access: Inside Nature’s Giants from here.
For those who live in Canada, you can obtain: Inside Natures Giants here.
For Germany: Inside Nature’s Giants.
For France: Inside Nature’s Giants.