The narwhal, an Arctic whale, has long captured the human imagination, earning it the nickname “unicorn of the sea.” This reputation comes entirely from its remarkable tusk, a long, spiraled projection that extends forward from the animal’s head. While the tusk is a defining characteristic of the species, its presence leads to frequent questions regarding sexual differences within the population. It is commonly assumed the tusk is exclusive to males, yet the biological reality is more complex.
Tusk Growth in Female Narwhals
The widely accepted pattern is that the tusk is a male secondary sexual characteristic, developing predominantly in males. However, the answer to whether female narwhals grow tusks is yes for a minority of the population. Scientific observation indicates that approximately 15% of female narwhals will develop a tusk, representing a natural variation within the species.
Female tusks are generally shorter and less conspicuous than those found on adult males. While a male tusk can reach lengths exceeding 2.5 meters, a female’s tusk rarely achieves that scale. The presence of a tusk in some females confirms the genetic potential for the trait exists across both sexes. One recorded instance of a tusked female measured between 146 and 151 centimeters in length.
Anatomy of the Narwhal Tusk
The remarkable tusk is not a horn at all, but rather a tooth—specifically, the animal’s upper left canine tooth. It erupts from the jaw, piercing the upper lip to grow straight out in a distinct counter-clockwise spiral. The longest recorded tusks have been measured close to three meters in length.
The tusk is primarily composed of dentine, but its external structure sets it apart from teeth in most other mammals. It lacks the hard enamel layer typically found on the exposed portion of a tooth. Instead, the outer surface is covered in a porous cementum layer containing millions of microscopic tubules. These tubules channel directly inward toward the pulp layer, which is densely packed with nerve endings connected to the narwhal’s brain. This unique structure transforms the tooth into a highly sensitive external organ.
The Tusk’s Role in Narwhal Behavior
The highly innervated nature of the tusk suggests its primary function is sensory, allowing the narwhal to perceive its environment. By sweeping the tusk through the water, the animal can detect subtle changes in water salinity, temperature, and pressure. This capability helps the narwhal navigate the complex, icy waters of the Arctic and locate areas of open water. The tusk may also aid in finding food by sensing chemical changes associated with prey.
The tusk is also involved in male-to-male interactions. It serves as a visual display of dominance and social status, with larger tusks signaling a more powerful mate. Males engage in “tusking,” a behavior where they gently cross and rub their tusks. This behavior may be a form of social bonding, a method for sharing sensory information, or a way to clean the sensitive organ. Drone footage has also documented narwhals using their tusks to strike and stun Arctic cod before consuming them.