The sign is quite common in Danish zoos where it translates to “crawls not up” and discourage kids from sitting on top of parapets (and possibly tumbling down into the clutches of irritated bears and even angrier attendants). The capital city is famous for its Copenhagen buns that are full of raisins and topped with icing. If the attendants fed these to the animals before opening up the gates, then the kids could maybe crawl back up again, and they might be able to remove the sign.