When a male gentoo penguin "falls in love" with a female penguin, he searches the entire beach to find the perfect pebble to present to her.
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Dolphins have names for one another.
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In 2011, archaeologists discovered the skeletal remains of a Roman couple who have been holding hands for 1,500 years.
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Sandy, an African Penguin, has been in 'love' with her keeper at the Nuremburg zoo since 1996.
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