Giraffe - The Facts
One of the distinguishing characteristics of the giraffe is its long neck.
With the aid of its long neck, a giraffe is able to reach leaves, fruit and flowers high up in Acacia's and other sought after tree species. It is thus equipped to exploit a 6 foot band of foliage beyond the reach of all other terrestrial browsers except the elephant. The 18 inch (45 cm) tongue and a modified atlas-axis joint that lets the head extend vertically further increase the height advantage. Giraffe can browse the crowns of small trees; big bulls can reach 19 feet, a yard higher than cows. They feed mainly on broad leaved deciduous foliage in the rains and on evergreen species in other seasons.
The giraffe's height also helps it to keep a sharp lookout for predators across the wide expanse of the African savanna, essentially a tall 'sentinel'.
Bulls, although also cows have been observed, have developed an elaborate ritualized fight called 'necking' that helps to most likely establish dominance. They repeatedly swing their long neck to deliver powerful head-butts to their rival's body and underbelly. A reinforced skull usually absorbs the impact of these blows, but occasionally an animal is knocked unconscious and very rarely even dies during such a fight.
4. Blood Supply
A giraffe's heart, which can weigh up to 11 kg, has to generate around double the normal blood pressure for a large mammal in order to maintain blood flow to the brain against gravity. In the upper neck, a complex pressure-regulation system called the the rete miribale prevents excess blood flow to the brain, when the giraffe lowers its head to drink. Conversely, the blood vessels in the lower legs are under great pressure (because of the weight of fluid pressing down on them). In other animals, such pressure would force the blood out through the capillary walls. Giraffe, however, have a very tight sheath of thick skin over their lower limbs which maintains high extravascular pressure in exactly the same way as a pilot's g-suit.
Surprisingly, even with its long neck, the giraffe has the same number of vertebrae in its neck as humans do. Giraffe have seven cervical vertebrae, but each one can be about 10 inches long.