When a hippopotamus opens its mouth, the large, elongated structures visible often raise a common question: are these tusks or teeth? While visually imposing, these are not true tusks. Understanding a hippo’s unique dental features requires a closer look at their anatomy and function.
Hippo’s Unique Dental Anatomy
What often appears to be a hippo’s “tusks” are, in fact, highly specialized and enlarged teeth. Hippos possess a complete set of heterodont teeth, meaning they have different types of teeth, including incisors, canines, premolars, and molars. An adult common hippopotamus typically has 36 teeth. The most striking are the large, curving lower canines and the prominent incisors, which can grow continuously.
The lower canine teeth can reach impressive lengths, sometimes exceeding 50 centimeters (20 inches), while incisors can grow up to 40 centimeters (16 inches) long. These large teeth are primarily composed of dentin, a bone-like tissue, with an outer layer of enamel. Unlike the flat, grinding molars found further back in the mouth, these elongated front teeth are not primarily used for consuming their herbivorous diet. Their continuous growth is balanced by constant wear as the hippo grinds them together, maintaining their sharpness.
Functions and Growth of Hippo Teeth
These specialized teeth serve multiple functions beyond just processing food. While hippos are herbivores, feeding on grasses and aquatic vegetation, their large canines and incisors are not used for grazing. Instead, they play a significant role in defense against predators and during territorial disputes. The powerful jaws and sharp teeth allow hippos to inflict serious wounds when threatened.
Within hippo social structures, these teeth are also important for dominance displays and ritualized combat among males. Male hippos often engage in fierce battles over mating rights or territory, using their elongated canines to challenge rivals. The size and prominence of these teeth can signal an individual’s strength and dominance. The continuous growth of these teeth ensures they remain functional despite the considerable wear and tear from such aggressive interactions and daily use.
Distinguishing Hippo Teeth from True Tusks
The distinction between a hippo’s enlarged teeth and what are scientifically classified as “true tusks” lies in their biological origin and structural characteristics. True tusks, such as those found in elephants and walruses, are specialized, continuously growing teeth that protrude significantly from the mouth. Elephant tusks, for example, are elongated incisors, while walrus tusks are elongated canines. A defining characteristic of true tusks is that they often lack a complete enamel covering, being primarily made of dentin, and grow continuously from a pulp cavity that extends far down into the tusk.
While hippo canines and incisors are large and continuously growing, they are structurally more akin to typical teeth that happen to be greatly enlarged. They maintain a more complete enamel layer and are rooted within the jaw in a manner consistent with other teeth, even though they project prominently. True tusks are typically extra-oral, meaning they extend well beyond the mouth and are often used for purposes like digging, lifting, or specialized combat, which differs from the primary function of hippo canines within the oral cavity. Therefore, while visually imposing and often referred to colloquially as tusks, a hippo’s formidable dental structures are technically specialized teeth.