The structures that resemble horns on a giraffe’s head are not classified as true horns or antlers, but are instead called ossicones. This term refers to the unique, permanent, skin-covered bony projections found exclusively on giraffids, which include the giraffe and its relative, the okapi. Both male and female giraffes possess these head ornaments, making them the only mammals born with these cranial features. The ossicones serve multiple purposes beyond mere appearance.
Ossicones: Defining the Giraffe’s Headgear
Ossicones are unique structures derived from ossified cartilage, meaning cartilage that has hardened into bone. They are permanently covered with skin and fur that blends seamlessly with the surrounding coat, distinguishing them from the headgear of other ruminants. The word “ossicone” itself is a compound term, referencing the bone composition and its conical shape.
These structures are fundamentally different from the true horns found on cattle, sheep, and goats, which consist of a bony core encased in a permanent sheath of keratin. True horns are never shed and grow continuously throughout the animal’s life. Ossicones also differ from antlers, such as those found on deer, which are pure bone, typically branched, and shed and regrown annually.
Ossicones do not protrude through the skin like horns or antlers. They are highly vascularized and innervated, containing a dense network of blood vessels and nerves that attach the bone core to the skull with specialized connective tissue. Giraffes typically have a pair of ossicones located above the parietal bones, and males often develop a third, median ossicone on the frontal bone of the forehead.
How Ossicones Grow and Develop
The development of ossicones begins while the giraffe calf is still in the womb. They start as soft, cartilaginous knobs of dense connective tissue positioned over the parietal bones. At birth, the structures lie flat against the head, which is believed to prevent injury to the mother during delivery.
Shortly after birth, the process of ossification begins, transforming the soft cartilage into a bony core. The ossicones remain separate from the underlying skull bone for the first few years of the giraffe’s life, connected only by vascularized tissue. This initial detachment allows for flexibility and continued growth as the calf matures.
Fusion of the ossicones to the skull occurs around the time the giraffe reaches sexual maturity. Once fused, they become a complete bony union with the skull, though bone deposition continues on the surface beneath the skin, increasing their size and density throughout adulthood. The ossicones of males generally grow larger and accumulate more bony deposits than those of females.
The Role of Ossicones in Giraffe Life
Ossicones serve multiple roles, with their most prominent function being as weapons in male-to-male combat known as “necking.” During necking, male giraffes swing their long necks, using the head and the heavy, bone-tipped ossicones to deliver powerful blows to an opponent’s body and legs. They are used to establish dominance and secure mating rights within the social hierarchy.
The appearance of the ossicones provides a clear visual indicator of a giraffe’s sex and social history. Male ossicones tend to be thicker and often have bald, battered tips due to the frequent rubbing and striking involved in necking combat. In contrast, female ossicones are generally thinner and retain a tuft of fur at the tips.
Beyond combat, the extensive network of blood vessels within the ossicones suggests a secondary function in thermoregulation. Scientists hypothesize that modulating blood flow through these highly vascularized structures helps the giraffe dissipate excess heat in the hot savanna environment. Ossicones also contribute to visual display and social signaling, with their size and shape communicating information about the animal’s age, maturity, and strength.