As to make sure these animals won't get bored, they give them fish frozen in a large chunk of ice. That way they'll have something to do: they have to open up the block of ice by either smashing it on a rock, or by throwing a rock on the chunk of ice.
LOL, but now suppose he is hungry an is unable to open the chunk of ice to get to that fish.... he will probably be as angry as someone whose work on his computer is lost because of a crash (and often the cause of many sightings of IFCs = Identified Flying Computers ).
Thanks for posting this! This explains it and is so interesting. It is sad though that humans make captive animals behave in unnatural ways... but this does explain alot. I wonder how much of the learned unnatural behaviours get passed into genes as captive animals breed....