The Arctic's 'corpse-whale' uses a sensory sword to navigate the deep
Known as the 'unicorn of the sea,' the narwhal possesses a spiralled tusk that is far more than a decorative weapon. This extraordinary organ is a highly sensitive sensory tool, capable of detecting subtle shifts in the freezing waters of the Arctic.
The narwhal's name, derived from the Old Norse 'nárhval' (corpse-whale), likely refers to its mottled grey skin and its habit of 'logging'—remaining motionless at the water's surface during summer. While the iconic spiralled tusk is most prominent in males, reaching lengths of up to 3.0 metres (9.8 ft), it is actually a protruding left canine. This tusk is highly innervated with millions of nerve endings and covered in tiny holes, allowing seawater to enter. This enables the animal to sense environmental changes such as water salinity, temperature, and pressure.
Beyond sensing, the tusk may serve social and survival functions. While scientists debate whether it is used for fighting or mating displays, recent drone footage from 2016 in Nunavut suggests a more practical use: narwhals may use their tusks to tap and stun Arctic cod during feeding. Interestingly, the species' evolutionary history is complex; while they are closely related to belugas, a 2019 DNA analysis confirmed that a hybrid specimen found in West Greenland around 1990 was indeed a 'narluga,' a mix of the two species.
Survival in the extreme Arctic requires specialized biology. Narwhals are among the deepest-diving cetaceans, reaching depths of 2,370 metres. To support this, they possess slow-twitch muscles and high levels of myoglobin to manage oxygen during prolonged dives. They also exhibit a rare evolutionary trait: menopause. A 2024 study suggests that post-menopausal females may live longer to provide essential assistance in rearing calves, which are particularly difficult for a single female to raise alone.
Source: Narwhal
