The mere fact he collects stones before the zoo opens does suggest they anticipate things. However, it would be nice to see that he's anticipating something based on experience. If the Zoo's closed on Monday because it's a national holiday, does he still collect stones? Or is something the trainers doing tipping him off to people arriving?
But seriously, arming him with a Super Soaker will be awesome. He will get stress relief, children will enjoy it and zoo will get more money.
(The footage was in the BBC series Planet Earth. Amazing series.)