A team of scientists has discovered the purpose of narwhal horns. Narwhals are a species of toothed whale that are most closely related to the beluga whale. The males have evolved an extra long left canine tooth that can grow up to 2.7 meters or 9 feet long, bursting through the upper lip and protruding from the head like the horn of a unicorn. In a research published in PLOS One, it was revealed that the tooth provided narwhals with the most directional sonar of any species on Earth.
Echolocation, also referred to as bio sonar, is used by many species of marine mammals. Many dolphins and whales use bio sonar to navigate the ocean without straining their eyes. A team led by Kristin Laidre, an ecologist at the University of Washington, decided to investigate the echolocation skills of narwhals by placing waterproof sound-recorders or hydrophones at 11 pack ice sites in Baffin Bay, West Greenland.
Previous theories had suggested that the "horns" of narwhals (Monodon monoceros), signalled testicle size to the females and were sometimes used in battles like a fencing foil. But given the living conditions of narwhals in the extreme Arctic waters under large blocks of ice, Laidre wondered if perhaps there was another use for the narwhal tooth. "You don't see open water for miles and miles and suddenly there's a small crack, and you'll see narwhals in it," Laidre stated in an interview with The New York Times. "I've always wondered how do these animals navigate under that, and how do they find these small openings to breathe?"
It was observed that narwhals produce clicking sounds and listen to the echoes to reconstruct their surroundings based on how those sound waves bounce off nearby objects or organisms. Laidre and her team discovered that instead of using their sonar skills like a floodlight to take in a vast array of objects all at once, narwhal clicks were extremely directional, allowing them to hone in on things like a flashlight.
Narwhals piece together more detailed snapshots of their environment with the highest resolution reconstruction of any animal on Earth by using their long, porous tooth. In 2014, researchers found that the tooth had foregone the protection of hard, external enamel to make it sensitive to even the tiniest of stimuli. "Sea water enters the horn through cementum channels, which are also present in human teeth," reported lead author Martin Nweeia, a marine mammal biologist from the Harvard School of Dental Medicine. "The liquid then travels through a network of tubules to the centre of the tooth, heading base of the tusk. There, the water excites nerve endings in the pulp of the tooth, sending signals to the brain of the animal."
Laidre and her team now have to figure out how to discover more narwhal secrets to help conserve the species in an already warming environment.
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