A crow carries a jar lid to the top of a sloping snowy rooftop in Russia. Sitting on the lid and sliding down the roof, you could think of it as surfing. It picks up the lid and repeats this behaviour again and again (Figure 1A). A group of black swans ride the crest of a wave that also looks like they are surfing. Once the wave reaches the beach, the swans fly back to another wave crest and perform the same actions again (Figure 1B). In both cases, the birds’ behaviours do not seem to provide any obvious function apart from enjoyment — they look like they are having fun. Videos of these behaviours received millions of views on YouTube, so we appear to like watching other animals having fun. But is this interpretation of the birds’ actions as having fun pure anthropomorphism or is it possible that an animal can act solely for its own enjoyment?This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.cub.2014.09.02
