Fom the newsletter of the Jerusalem Biblical Zoo.
Translated from the Hebrew by Nomi Friedman.

A known and ugly phenomenon in zoos all over the world is visitors who willfully throw things at the animals on display, especially at chimpanzees. In the best case, food is thrown, and in the worst, to our regret, we have seen rocks thrown. We are seeing a significant improvement in the public's conduct, but the crowds that throw stones at chimps are not our concern here. In Jerusalem the talk is of rock-throwing chimps.
When a large crowd gathers opposite Niki and Galine, the young chimpanzees leave their other chimp activities, race about looking for stones, and start throwing them at the crowd. Why do they do this? Since this is Jerusalem, it might be a way of blowing off steam, or maybe it's an expression of rebellion and independence.
A separation fence was decided upon. In the past few weeks, the wall was built...green, light, elastic, and high. It fulfills its requirements, and is simple and elegant. It has proven effective in stopping the stones.