Karta, a 27-year-old primate, cleared one fence and began piling up debris to scale a wall at Adelaide Zoo.  Visitors who witnessed the escape alerted staff, and the zoo was promptly evacuated and closed for the day.

But Karta spent less than 30 minutes on the loose before apparently thinking better of her escape attempt.  Zoo curator Peter Whitehead told reporters the ape seemed to realise she was in a place where she should not have been.

"She's actually hung on to the wall and dropped back into the exhibit," he said.  It was not the first time Karta had caused a headache for the zookeepers.  "You're talking about an animal that's highly intelligent," Mr Whitehead said.

"We've had issues with her before in normal day-to-day operations where she tries to outsmart the keepers. She's an ingenious animal."  The zoo offered a refund to visitors after closing down for the day, but few zoo-goers seemed flustered by the drama.  Ryan Johnston, 11, told ABC News he had seen Karta's escape, and described it as "amazing".