Narwhals: what a tusk can tell us and what remains uncertain

A tooth that grows outward

The narwhal (Monodon monoceros) is an Arctic toothed whale without a tall dorsal fin. Its most conspicuous feature is usually a long tusk projecting from the head, but anatomically that structure is an elongated upper-jaw tooth, not a horn arising from the forehead. In most males, the left tooth erupts and develops into the spiral tusk while the right tooth stays embedded in the skull. [1]

That pattern is common, not universal. Most females retain embedded teeth, yet rare females grow tusks. Some males have no visible tusk, and occasional narwhals have two. A tusk seen clearly can therefore support an identification as a tusked narwhal, but it cannot by itself establish sex. A distant animal with no visible tusk might have an embedded tooth, or the view might simply fail to show the head clearly. [1]

Reading the animal, not just the tusk

Adult males average longer in body length than females, but body length excludes the protruding tusk. A measurement that adds the tooth is therefore not directly comparable with a body-length measurement. Age, sex and the measurement convention all matter when comparing animals. [1]

Color can offer another clue to life stage, though not a precise age estimate. Narwhal skin changes from darker juvenile coloration to a mottled adult pattern and may become very pale in old animals. These are broad patterns; a photograph’s lighting, distance, and water conditions can make coloration harder to judge. The pattern does not yield an exact age or lifespan. [1]

The species is associated with Arctic waters, and Canadian narwhals are assessed as distinct subpopulations rather than as one interchangeable local group. Their cultural and nutritional importance to Inuit communities is part of the species’ human context as well as its biology. Neither a visible tusk nor a general species description identifies which Canadian subpopulation an individual belongs to. [1]

What observations show the tusk doing

A 2025 study analyzed drone-recorded encounters in Creswell Bay, Nunavut, involving narwhals and Arctic char, sometimes with gulls present. The footage captured narwhals using their tusks to strike and manipulate fish and to influence fish movement. These are recorded actions in particular surface encounters: they provide evidence that the tusk can be used in interactions with prey, rather than serving only as a display feature. [2]

The researchers also described exploratory behavior and behavior they interpreted as likely play. That extends the set of plausible uses supported by observation, but “play” remains an interpretation of what the animals did; footage does not directly reveal intention. Likewise, a fish strike is evidence of an action, not proof that every strike is a successful capture or that the tusk is necessary for feeding. [2]

Consider a hypothetical evidence-reading exercise: a clip clearly shows a tusk contacting a fish, then shows the fish changing direction. The clip supports the statements “contact occurred” and “the fish moved afterward.” It does not alone show how often this happens, whether the fish was caught, or whether narwhals use the same technique while feeding at depth. Keeping those steps separate prevents an observed action from turning into a complete theory of function. [2]

Several possible functions can coexist

The footage complicates a simple account in which the tusk has one settled purpose. Fish-directed use is compatible with a feeding role, but the study’s observations do not settle the tusk’s complete function. Sensory, social, exploratory, and foraging roles need not exclude one another; evidence for one use does not erase the possibility of others. A broader sensory explanation, in particular, should not be treated as proven merely because the tusk is an unusual tooth. [2]

There is also a sampling limit. The analyzed evidence concerns a small number of surface encounters in one bay. It cannot establish how frequently all narwhals use tusks in deep-water feeding, whether different populations behave alike, or how often a particular behavior occurs across a year. The study’s publication date is separate from the dates of its field encounters; the article was published on 28 February 2025, but that reporting date should not be mistaken for the date of a specific sighting. [2]

The most defensible reading is specific: the tusk is an erupted upper-jaw tooth, most often the left tooth of a male; visible tusks have exceptions as indicators of sex; and drone footage has documented fish-directed, exploratory, and likely play behavior in a particular setting. How those uses divide across feeding, sensing, display, and social life remains open. [1] [2]