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While many scientists believe that tool use among dolphins is a relatively new phenomenon, a 2017 study published in Biology Letters suggests that otters may have been using tools for millions of years. Sea otters frequently use rocks to break open well-armored prey, such as snails.

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If you thought your cat was sleepy, just wait until you hear about koalas. According to the Australian Koala Foundation, these cuties sleep between 18 and 22 hours a day. The koalas' diets require a lot of energy to digest, which is why they've got to nap so much.