There is a story of a man going to a zoo for the first time and, after staring at a giraffe in astonishment, exclaimed, ‘‘There ain’t no such animal!’’¹ Yet African giraffes have long been known to Europeans. They are the tallest living land animals in the world, and more recently have interested medical researchers. They may grow up to a height of 19 feet and live about 25 years in the wild and up to 39 years in captivity. Just as humans, they have only seven vertebrae but these are much elongated, up to ten inches each. Their necks may amount to almost half of their overall length yet unlike humans they do not suffer from degenerative joint diseases, spondylitis, or osteoporosis.

The main theory explaining their long necks is that over millions of years they adapted to reach the high branches of trees, especially acacias, and so became able to compete successfully with other herbivores. Another theory is that being tall lets them watch out for predators. Some scientists believe that having long necks helps male giraffes fight over females by striking their adversaries with armored heads and strong necks.^1,2

It is also believed that the giraffe’s unique body shape helps it regulate its temperature. By having a narrow body, the giraffe can keep most of its surface area out of direct sunlight, helping it to stay cool. Such long necks may also have developed through mutations of skeletal and cardiovascular genes over millions of years. Giraffes have excellent eyesight, and since they are so tall, they can see another animal from a mile or more away.

Giraffes have exceptionally strong hearts. A giraffe heart can weigh up to twenty-five pounds. Although their blood pressure can be twice as high as that of humans and reach figures of 280/180 mmHg and potentially rising to 350 mmHg, their arteries are elastic and have thick walls and valves that protect them from having strokes or heart failure. Their blood also contains a higher concentration of red blood cells to carry oxygen more efficiently.

The giraffe’s skin is another area of interest. Giraffes have thick, tight skin around their legs that helps maintain their high blood pressure and prevent fluid from pooling in the lower extremities. This feature could provide insights into human conditions such as chronic venous insufficiency.

Giraffes have also contributed to antibacterial research because of their impressive resistance to infections despite living in environments where diseases are prevalent. Their immune systems are highly efficient in fighting off pathogens; they have incredibly strong bones, capable of supporting their massive weight; and despite their height, they rarely suffer from bone fractures. Scientists are studying the composition of giraffe bones to understand how they achieve such strength and resilience, hoping to develop new strategies for preventing and treating osteoporosis.

Yet giraffes are also prone to develop a number of diseases. They are susceptible to developing Clostridium tetani infections and those in captivity need to be given tetanus toxoid every other year. Giraffe skin disease (GSD) is a poorly understood condition that causes wrinkled skin and incrustations as well as bloody infected lesions, affects the neck, shoulder, and limbs, and impedes mobility. It has been observed in seven sub-Saharan African countries and is particularly widespread in Tanzania. Giraffes may also develop Lumpy Skin Disease Virus (LSDV), a virus that has been isolated from a diseased giraffe in Vietnam.

Giraffes are also prone to many unsavory jokes: they are shunned in society because they are a pain in the neck; they are slow to apologize because it takes them a long time to swallow their pride; they do not make good pets because they are high maintenance; they get bad grades because they have their head in the clouds; they have long necks because their feet smell; and when you cross a giraffe and a pig you get bacon and legs.

References

1. Gregory JC. From myth to science. Science Progress 2009;92(3/4):387-99 [1922-23, XVII, 308-316].
2. Robert Simmons and Lue Scheepers. Winning by a neck: sexual selection in the evolution of giraffe. Am. Nat. 1996;148:771-86.
3. Elissa Z, Cameron EZ, and Toit JT. Natural History Miscellany. The American Naturalist January 2007;169(1).