Despite the extreme long neck of the giraffe, the animal has the same number of neck (cervical) vertebrae like humans and most mammals: 7. In fact, as paradoxically as it sounds, the giraffe has the shortest neck relative to the foot length amongst all hoofed mammals! That's why they have to execute
that clumsy maneuver with the fore limbs when having to drink water or graze.
To pump the blood high to the brain, the heart of the giraffe is very large: up to 11 kg (25 pounds). The heart pushes 60 liters of blood per minute. The muscles of the neck arteries are relaxed with each heart beat, helping the propulsion of the blood to the brain. In the neck veins, special valves impede the blood to flow back too rapidly, meanwhile preventing the emergence of a syncope (fainting due to sudden lowering of the blood pressure). At the base of the feet, where pressure is low, there is a system of capillary vessels like in humans, impeding the appearance of edemas. Like humans, the giraffe is one of the few vertebrates which is taller than longer, and NASA studied blood circulation in giraffes for creating an anti-gravity garment for astronauts.
The tongue of the giraffe is 54 cm (1.8 ft) long, being the most powerful and muscular amongst all hoofed mammals. The tongue and the roof of the mouth are so tough, that the giraffes can feed on the leaves of the thorniest Acacia trees.
The giraffe female weighs one tonne; the male up to 1.5 tonnes. A kick can crash the skull of a lion, that's why lions attack only isolated giraffes. Due to their height, giraffes spot the lions from distance. Males fight for the right of mating through necking (neck fights). The noise of the fight can be heard 50 m (166 ft) away. A 15-year old bull has a 10 kg (22 pounds) heavier head than younger males, and with this difference, he can kill young bulls through necking. That's why only males of the same size use to engage in combats, which are not bloody. The defeated males retreat galloping. Sometimes, the winner mounts the defeated bull, a clear dominance sign. In fact, homosexual sex is common in giraffes and before mounting, the partners can affectionately rub their necks up to an hour. 5 % of the male giraffes are found in any moment involved in homosexual contact.
Males never use kicks in fights between them, even if using them against predators.
Both giraffe males and females wear horns, which are covered by hair tufts. Still, the horns of the males are more massive and with a hardness resembling marble.
Newborn giraffes have the height of a man. At the age of 6 months, they are already 3 m (10 ft) tall and, by the age of 7 years, they are 5 m (16.6 ft) tall. Usually, males reach 5.5 m in height, while females are 1 m shorter. That's why males eat shoots above 4 m, while females and offspring (which are 2 m at birth) are restricted to shoots at the height of 2 to 4 m.