The visitors can get rather too close to the Gorillas, particularly when they are inside, or rather the silverback Kumbuka who is an individual male who still happens to relate to people quite a lot, cannot get far enough away as the indoor enclosure is (IMO) not really deep enough. I think he hits the outside windows too, hence this attempt at covering/masking. So they have to resort to calming measures like screening the windows and having volunteers on duty at busy periods to reduce noise etc. to stop him hitting the glass. I think as he matures this behaviour will die away though but deepening the exhibit den would help too, though that's a very expensive undertaking and so unlikely to happen I would think.
The previous male(s) in this enclosure, had a very different, quieter temperament so there was not the same problem then.
