The giraffe is one of Africa’s most immediately recognizable mammals, characterized by its towering height and distinctive spotted coat. This striking animal belongs to the biological family Giraffidae, a small group of hoofed mammals that possess a unique combination of physical traits. The Giraffidae family contains only two living members today.
Placing Giraffes in the Animal Kingdom
Giraffes are classified into the Class Mammalia, as they are warm-blooded, hair-covered animals that nurse their young. They belong to the Order Artiodactyla, which encompasses all even-toed ungulates. This order includes diverse groups such as pigs, hippopotamuses, camels, cattle, and deer, all sharing the characteristic of having an even number of toes on each foot.
The Artiodactyla order places giraffes within the Suborder Ruminantia. Ruminants are defined by their specialized digestive system, which involves a four-chambered stomach. This system allows them to ferment and efficiently digest tough plant matter through regurgitation and re-chewing (cud). This places them alongside animals like cattle, sheep, goats, and antelopes.
Within the Ruminantia suborder, Giraffidae stands as its own distinct family, separate from families like Cervidae (deer) or Bovidae (cattle). Although these groups share the digestive process of rumination, the physical and skeletal features of giraffids set them apart. Their closest living relatives among the ruminants are the pronghorn and the members of the deer family.
Shared Biological Traits of Giraffidae
The family Giraffidae is defined by unique morphological characteristics that distinguish its members from all other ruminants. The most prominent shared feature is the presence of ossicones, which are permanent, bone-cored, skin-covered structures projecting from the skull. Unlike the antlers of deer, which are shed annually, ossicones develop from cartilage and fuse to the parietal bones of the skull, remaining throughout the animal’s life.
Ossicones are present in both male and female giraffids, though they are larger and more pronounced in males. These structures serve various purposes, including thermoregulation and use during intraspecific combat, particularly among males establishing dominance. The bony core is covered in skin and hair, not velvet.
Another defining trait is their specialized dental structure, adapted for browsing on leaves and buds. Like other ruminants, giraffids lack upper incisors, instead possessing a hardened dental pad against which the lower incisors and canines shear vegetation. The lower canines are lobed and form a broad, rake-like structure for stripping leaves from branches.
The locomotion of giraffids is also distinctive, primarily characterized by a pacing gait at slower speeds. During a pace, both legs on one side of the body move forward simultaneously. This is an unusual pattern among large ungulates and contrasts with the diagonal trot used by many other four-legged animals.
The giraffe’s towering stature necessitates a highly specialized cardiovascular system. To pump blood effectively up the long neck to the brain, giraffids have a powerful heart that generates high blood pressure. They also possess complex valves and thick-walled blood vessels to regulate blood flow and prevent blood pooling when the animal lowers its head to drink.
The Two Surviving Genera: Giraffe and Okapi
The family Giraffidae contains two living genera: Giraffa (the giraffe) and Okapia (the okapi). The genus Giraffa is immediately recognizable by its extreme height, which allows it to browse on vegetation inaccessible to most other herbivores on the African savanna. The giraffe’s neck is supported by seven highly elongated cervical vertebrae, the same number found in most mammals.
Giraffes are social animals that inhabit the open woodlands and savannas across sub-Saharan Africa. The genus Giraffa is further subdivided into several distinct species and subspecies across its range.
The okapi (Okapia johnstoni), often called the “forest giraffe,” occupies a vastly different ecological niche. Okapis are restricted to the dense, equatorial rainforests of the Democratic Republic of Congo. Their appearance features a reddish-brown coat and striking horizontal black and white stripes on their legs and hindquarters.
The okapi possesses the family’s defining ossicones, though they are much smaller than those of the giraffe and are typically only present in males. Unlike the giraffe, the okapi has a much shorter neck, proportionate to its smaller body size, making it resemble a zebra or a horse. The okapi also exhibits solitary and elusive behavior, contrasting with the social herds of the giraffe.
Evolutionary History of the Giraffids
The Giraffidae family originated in Asia during the Miocene epoch, approximately 25 to 5 million years ago. From this ancient center, the family diversified and spread across parts of Europe and into Africa. The fossil record indicates that early giraffids were far more widespread and diverse than the two surviving genera are today.
Many ancient giraffids had much shorter necks than the modern giraffe, and some possessed highly complex, branched ossicones. These extinct forms demonstrate that the family experimented with various body plans and head ornamentation. This diversity included large, robust relatives such as Sivatherium, which had massive, elaborate, shovel-like ossicones.
The lineage leading to the modern giraffe and okapi began to diverge as they adapted to different environments. The long-necked form arose later, likely driven by feeding competition for high-level vegetation in the expanding African grasslands. The okapi lineage retained more primitive features, adapting to the closed-canopy forest environment.