@snowleopard Very sad indeed. It is bad enough that vandalism is so common in cities (and it also is in cities like Antwerpen, Brussels or even smaller cities like Mechelen, Leuven and Lier), but for it to happen in a zoo just makes me upset. Unfortunately this isn't even nearly the worst Artis has had to deal with, as a few years ago people actually broke into the zoo, which also resulted in the death of at least one animal (a pelican).
Fortunately I haven't seen too many cases of it vandalism at the zoos I have been to, and if I do see it is usually limited to, say, writing unreadable idiocy and obscenities with permanent markers, often in bathrooms. That is bad enough, but in the perspective things of how bad things can get...
I do remember one egregious case from Antwerp from years ago, where walls of historical buildings had stuff written on them with permanent markers by members of a high school group, who also found it necessary to apply their markers to a babirussa as well as to poke the babirussa with a pocket knife.
All I can say is, we humans are supposed to be the highest primates but many of our species sure don't act like it.