The new reinforced glass barrier will surround the chimpanzee exhibit at Jerusalem's Tisch Family Zoological Gardens, zoo director Shai Doron told reporters.
"Chimps know how to throw forehand, but can't throw overhand, like a baseball. So usually the rocks they throw have a big arc and people have time to escape," he said.
Rather than covering the chimpanzee compound with rocky Jerusalem soil, it will be covered with a deep layer of fresh soil without the rocky weapons, he said.
"It's kind of embarrassing to be stoned by a chimp," Doron told The Jerusalem Post.
The chimpanzee rock-throwing draws large crowds even though it is a sign the animals are upset, he said. Visitors think it's funny "until they get a rock in the head," Noa Danen, head of the zoo's primate section, told the newspaper.
The money for the two-month refurbishment came from the zoo's endowment fund and was supplemented by a grant from the Tourism Ministry, the paper said.