The narwhal, often called the “unicorn of the sea,” is an Arctic whale distinguished by a single, long, spiraled projection extending from its head. This striking feature has fueled centuries of speculation about its purpose in the harsh, icy environment. Its defining characteristic is a fascinating example of extreme sexual dimorphism in nature. This unique structure raises immediate questions about which individuals possess it and what role it plays in the animal’s life.
Tusk Presence in Female Narwhals
The most noticeable difference between male and female narwhals is the presence of the long, spiraled tusk, which is predominantly a male characteristic. The vast majority of adult male narwhals develop this elongated tooth, making it a clear sign of sexual dimorphism within the species. However, a small but notable percentage of females also grow a tusk, directly answering the question of whether they possess one.
Approximately 15% of female narwhals will develop an elongated tusk, though these are typically shorter and have a less pronounced spiral than those found on males. This suggests that while the tusk is not exclusively male, its development in females is a biological anomaly rather than a species-wide trait. The presence of a tusk does not appear necessary for female survival or reproduction, given that the majority of the female population does not have one.
Anatomy and Misconceptions
The narwhal’s head projection is incorrectly referred to as a horn, which is a common misconception. A horn is composed of keratin and bone, but the narwhal’s projection is actually an overgrown canine tooth. This single tooth, typically the upper left canine, erupts through the lip and can grow up to 10 feet long, coiling in a consistent counter-clockwise spiral.
The structure is not a solid piece of ivory; it is a flexible, hollow tooth unlike any other in the animal kingdom. Unlike human teeth, the narwhal tusk lacks a tough enamel layer protecting the sensitive pulp core. Instead, the outer surface is covered in millions of tiny tubules—fluid-filled channels that allow direct contact between seawater and the internal nervous system. This unique anatomy essentially makes the narwhal’s tusk an “inside-out” tooth, capable of relaying external environmental information directly to the brain.
Functions of the Narwhal Tusk
The unique structure of the narwhal tusk points to two primary functions: sensory perception and sexual selection. The millions of nerve endings in the tusk allow the whale to detect subtle changes in its Arctic environment, transforming the tooth into a sophisticated sensory probe. Studies show that the tusk can sense variations in water salinity and temperature, which helps the narwhal navigate and locate feeding areas near ice formations.
The sensory information gathered by the tusk is so direct that exposing it to different salt concentrations causes a measurable change in the narwhal’s heart rate. This ability provides the whale with environmental monitoring crucial for survival in the Arctic waters. However, the tusk’s role in the male social hierarchy is equally significant, functioning as a secondary sexual characteristic.
The length and condition of a male’s tusk serve as a visual signal of his health and social status to both rivals and potential mates. Males are frequently observed engaging in “tusking,” where they cross and rub their tusks together, which is believed to be a form of dominance display or a way to maintain the tusk’s surface. Recent observations suggest the tusk is also used in foraging, with narwhals seen using it to strike and stun Arctic cod before consuming them.