The massive, pointed structures protruding from a hippopotamus’s mouth often cause confusion, leading many to wonder if they possess horns. The direct answer is that hippos do not have horns. Understanding why requires examining the anatomical definition of a true horn.
Defining True Horns
True horns are permanent, unbranched anatomical structures found almost exclusively on members of the family Bovidae (cattle, sheep, goats, and antelopes). A true horn is composed of two distinct, fused layers. The innermost layer is a core of living bone, which is an extension of the skull’s frontal bone.
This bony core is covered by a dense, protective outer sheath made of keratin. Keratin is the same fibrous structural protein that forms human fingernails, hair, and the outer layer of skin. Unlike antlers, true horns are never shed and continue to grow throughout the animal’s life.
Hippo Dental Anatomy
The large, pointed growths on a hippopotamus often mistaken for horns are actually highly specialized teeth, accurately described as tusks. These structures are the hippo’s enlarged canine and incisor teeth. The lower canine tusks are the most noticeable and are the longest teeth of any terrestrial animal.
These lower canines can grow to impressive lengths, reaching up to 72 centimeters (about 28 inches) in males. The tusks are composed primarily of dentine, also known as ivory, which is the same material found in elephant tusks. Unlike typical teeth, hippo tusks grow continuously throughout their lives. They function as weapons for defense and in aggressive displays between males establishing dominance, rather than for grazing.
Tusks Versus Horns
The fundamental difference between the hippo’s tusks and a true horn lies in their composition and origin. A tusk is a modified tooth, rooted in the jawbone and composed of dentine or ivory. A true horn, in contrast, is a projection of the skull’s frontal bone covered in a keratin sheath.
The continuous growth of a hippo tusk originates from the dental pulp cavity within the jaw. Conversely, a true horn grows from the skin surrounding the bony core on the head. Since the hippo’s pointed structures are composed of ivory and emerge from the jaw, they are classified exclusively as tusks. The absence of the bony core and keratin sheath confirms the hippopotamus does not possess true horns.