Quokkas: These animals are known for their "smiles" and friendly personalities. However, their "smiles" are mainly due to the shape of their mouths.
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Dolphins: These intelligent animals are known for their friendly behavior and playful nature. When they smile, their mouths curve upwards.
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Sloths: The facial structure of a sloth can make it appear as if they are constantly smiling.
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Dogs can smile when they pick up on your happiness and respond in kind.
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Chimpanzees: Some research suggests that chimpanzees can smile in the same way as humans. However, when chimps bare both their top and bottom teeth, it may be a sign of fear.
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Polar bears smile to express contentment, just like humans do. They pull the sides of their mouths upwards.
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Zebras smile to greet each other and to communicate with other zebras. This smile is a bared-teeth grimace that's also known as the Flehmen response.