Just off the top of my head, there are birds that collect ornaments to decorate their nests to attract a mate, fish that sculpt complex patterns into sand for the same reason, and an elephant and an ape or something that were trained to paint (by a human, so admittedly a bit of a stretch, but still)
Bears have also been observed stopping to just sit and watch a sunset/rise, so while I'm not aware of any actually producing art, there are at least examples of non-humans capable of appreciating the same type of beauty that many art forms seek to capture.
These are behaviors to attract a mate, so they serve a function and trigger an evolutionary response in the mate to be attracted. Just because the patterns and structures appear pleasing to us does not make them art.
There are pieces that are visually unappealing, but are with certainty still considered art.
I'd compile a list of different definitions of art (Beardsley, Danto, Dickie, Ranciere, Stock, Carroll, Zangwill etc.) and see if, given the context, the fabrications and behaviors of animals could be considered art - I've had similar conversations in the past and would love to take your position, but a better argument needs to be made in order to support that claim. Should I get a chance to do that homework anytime soon, I'll update this post.