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Narwhals use echolocation for foraging and navigation – this is the system used by bats on land. They produce pulses of sound and listen to the echoes to create an image of their surroundings.

Often dubbed the unicorns of the sea, narwhals are strange and beautiful creatures with long tusks protruding from their heads. Members of the population of more than 80,000 can weigh up to 4,200 ...