Why do Giraffes have knobs on their heads?

[JACQUE]

The "horns" on a giraffe's head are called ossicones. They are made of bone incased in skin. They are connected to the skull in adults, but they lie flat in newborns to facilitate easier birth. When the giraffe is born, the ossicones are made of cartilage (the stuff that gives your nose and ears structure). Slowly this cartilage is replaced with bone, starting from the tip. Fusion with the skull occurs at about 4 years in males and 7 years in females. Females have two ossicones and a slight bump along the middle of their snouts. Mature males have three ossicones (two above the ears and one in the middle of their face) and many bony bumps and knobs on their skulls. Male horn growth continues throughout their lifetime. Bone originating from the giraffe's skin tissue is deposited onto the skull, a bone-growth process unique to giraffes. The male's skulls are massive, weighing up to 30 lbs. They do not use their bony heads to impress females or attract mates. Instead, they use their heads as clubs to fight other males. A well-placed blow from another male giraffe's head, sent one male giraffe sprawling on the ground and left him unconscious for 20 minutes.