"As far as we know, the blue whale is the largest animal ever to have existed on the planet. Weights up to 190,000 kg (as much as 30-40 African elephants) have been recorded. They are also among the fastest swimmers, reaching a speed of 48 km per hour when chased. They eat 6-7 tons of krill, a small, shrimp-like crustacean, per day, by gulp-feeding. With each gulp, the whale's throat stretches along a series of grooves, enlarging the mouth’s capacity, then the water is expelled and the krill remain, trapped by baleen plates. The blue whale's voice is the deepest of any animal's, and their vocalizations carry for thousands of miles underwater, at frequencies below the range of human hearing. This may enable them to communicate across oceans, and may be a sonar-like imaging system that helps a whale map its location relative to distant landmasses or deep underwater terrain. They can live for 80-90 years, and for centuries, blues whale were safe from humans because of their sheer size, but whalers on modern ships armed with harpoon guns drove them almost to extinction. They are protected now, but there is no sign yet that they are recovering from over-exploitation."

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Mammal Species of the World
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