I’m not sure why Marginal Revolution only just now linked to a Guardian article from 2003, but it’s still a seriously good read. The dolphin in the article was trained to help keep her pool clean by bringing any waste paper that falls into her pool to the keepers for a reward. Over time, one of the dolphins learned to trick the humans. Instead of immediately giving a big piece of litter to her keepers, she would hide it and only tear off small pieces to give to a keeper each time one passed, thereby earning more fish as a reward.

What’s even more impressive is that since she has also been trained to bring gulls (I’m not sure if they’re dead or alive at this point) that fly into her pool to the humans in return for a reward, she learned to keep some of the fish that she’d been given. Once the humans went away, she used the extra fish as bait to lure gulls to fly into her pool to catch them so that the humans would give her more fish for the gull. The rest of the article is filled with similarly fascinating anecdotes.

Science-fiction of course has long been full of stories about dolphins being intelligent, the entire plot of the fourth Star Trek film being the most obvious example. But this article lead me to thinking back to opinions of people like Australian SF author Greg Egan, who believes that our current treatment of some animals amount to human rights violations that will one day be recognized as a historically shameful era of our species.