Giraffe calves are born with ossicones, but these small boney cores surrounded by cartilage lie flat and unattached to the skull to prevent injury during birth. Shortly after, the ossicones begin to grow and ossify, transforming from cartilage to bone. This is called ossification. By the time giraffe reach sexual maturity, usually between 3-5 years, their ossicones are fully composed of bone and firmly attached to the skull.
Both male and female giraffe have a primary pair of ossicones on top of their heads. Female ossicones tend to be thin and often have tufts of hair, while male ossicones are generally thicker and often become bald on top due to frequent necking behavior.
In some giraffe species, particularly males, a second pair of ossicones may grow behind the first pair on the back of the skull, along with a prominent median ossicone on the forehead. The size of this median ossicone varies across species, with the northern and reticulated giraffe having considerably larger median ossicones compared to the Masai and southern giraffe. This variation serves as a key morphological feature for distinguishing between giraffe species.
Male giraffe regularly engage in necking contests to ascertain dominance using their ossicones. The bones of the ossicones and skull accumulate boney deposits or ossifications over time, increasing their weight. This allows them to deliver more powerful blows during necking contests. While fatal combat is rare, it can occur.
