Explain why giraffes have a long neck?

Dietary adaptation and access to high leaves

Giraffes have a long neck that allows them to easily reach leaves located several meters off the ground, where other animals cannot go. This advantage gives them access to a relatively untapped food resource, particularly fresh acacia leaves, rich in essential nutrients. Thanks to this adaptation, they can graze freely at height, thus avoiding competition with most other herbivores for food. They take advantage of this specialization to easily survive during dry periods or when low-growing vegetation becomes scarce.

Evolutionary advantages related to natural selection

A long neck offers giraffes quite a few advantages in terms of survival. Giraffes that can easily access leaves high in the trees had a better chance of survival during droughts or when low food was too contested. As a result, these better-fed individuals were stronger, lived longer, and had more offspring. Gradually, their genes that favored a longer neck spread. A long neck is also practical for scanning the surroundings. The giraffe can spot potential predators like lions from a great distance, which increases its chances of escaping danger. In summary, individuals with long necks adapted better to their environment: more efficient at feeding, more vigilant in detecting predators, and therefore better equipped to pass their genes to future generations.

Alternative theories on the evolution of giraffe necks

Some scientists suggest that the long necks of giraffes are linked to male competition rather than their feeding habits. Essentially, males with longer necks would have had an advantage in fighting and impressing their opponents during battles known as "necking." Another hypothesis proposes that it is an adaptation for better vigilance against predators, as giraffes can detect dangers from afar due to their greater height. These alternative theories remind us that the evolution of giraffes is more complex than simply reaching for leaves high up.

Anatomical comparison with other animal species

The giraffe's neck has seven cervical vertebrae, exactly like almost all other mammals, including humans and cats. However, unlike ours, their vertebrae are indeed huge: each vertebra can reach over 25 centimeters, far from our small vertebrae. In other animals like the whale, even though their neck appears short and massive, the number of cervical vertebrae remains constant at seven. In contrast, some birds, like the swan, have more cervical vertebrae, sometimes exceeding twenty, which allows them great flexibility, unlike the giraffe's rigid but very effective neck.

Physiological effects related to the elongated neck in giraffes

The long necks of giraffes impose unusual constraints: their hearts must work very hard to send blood all the way up. Giraffes therefore have an enormous hyper-muscular heart (almost 11 kg!) capable of generating blood pressure twice that of a human. Naturally, with such pressure, their bodies had to adapt: they have a special network of blood vessels in their necks equipped with valves that prevent blood from pooling in the head when they lower their heads to drink. Without these adaptations, they would risk fainting or even a brain hemorrhage every time they want to hydrate. Another crazy thing is that their lungs function differently because breathing efficiently with an extremely long trachea requires significant respiratory adaptation.