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Dr Susanna Blackwell is a Swedish-American marine biologist who studies the effect on marine animals of man-made sounds - from ships, drilling, anything unnatural. As part of that, she has been hanging out with narwhals. They are incredible looking beasts and males have a great long tusk. That's why they are known as the 'unicorns of the sea'. (Photo credit: David Fleetham/VW PICS/UIG/Getty Images.)
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