The St. Louis Zoo is nearing completion on a $198,000 replacement of observation windows at the orangutan exhibit after one of the apes broke four of them.

The 7-foot-tall windows were replaced in mid-November, but replacing the triple layer of glass with 3-inch thick acrylic required re-engineering the frames that hold them, plus a caulking process that requires 21 days to cure, zoo spokeswoman Susan Gallagher said.

The prime suspect in the vandalism is Rubih, a 12-year-old female nicknamed “Rockin’ Rubih” by zookeepers. They say Rubih tapped or banged rocks repeatedly against four of the six viewing windows over several months this year.

The habitat will reopen to the orangutans this month, although Gallagher said the outside temperature must be at least 50 degrees and sunny for the orangutans to go outside.

Zookeepers say Rubih was first caught banging rocks on the glass in the spring. The zoo’s professional ape care team successfully taught Rubih to instead bring rocks to them and be rewarded with a treat, but it didn’t end there.