Who is the most dangerous animal at the zoo? Why?

I think Pi is referring to humans.

The cruelty is often more active and direct. The literature contains reports on the many torments inflicted upon zoo animals: a shoebill dying of shock after having its beak smashed with a hammer; a moose stag losing its beard, along with a strip of flesh the size of an index finger, to a visitor's knife (this same moose was poisoned six months later); a monkey's arm broken after reaching out for proffered nuts; a deer's antlers attacked with a hacksaw; a zebra stabbed with a sword;