A zoo worker placed herself in a blind to observe the chimpanzee's behaviour and found that, for five consecutive days before the opening of the zoo, Santino gathered stones from the water and placed them in the caches.
The following year, the chimpanzee added pieces of concrete to his ammunition, and was observed gently knocking on concrete rocks to break off smaller, disc-shaped pieces.
Since the initial finding, caretakers at the zoo have removed hundreds of caches.
A cache of deadly projectiles intended for human targets.
They should have had Stone Day at the zoo and issued a rock to every visitor to throw at this scheming menace.