So we're not the only: - tool-using animal - fire-using animal - language-using animal - animal which domesticates other animals - animal which builds complex structures Aha! I know! We're the only animal which continually comes up with reasons why we're special.
How about: -art (cave paintings, etc) -music it's striking to see 6-12 month old infants bopping up and down to music. They're not taught to do this and I've never heard of animals responding to music...
And Whales have music: https://en.wikipedia.org/wiki/Whale_vocalization#Song_of_the... -- their singing employs musical rhythm and phrasing, and is culturally transmitted rather than instinctual.
Scientists are generally quick to give such vocalisations -- along with bird song, etc. -- purely functional attributes, thereby dismissing any aesthetic or emotional meaning it might have for the animal. "It's a territorial signifier". "It's for mate selection." Etc. This is a mistake: Mozart used his music to get laid; what musician doesn't? We can't know what these sounds truly mean -- subjectively, not functionally -- to an animal, because we can't talk about it with them. But that doesn't mean that it is empty of meaning.