Zookeepers say a group of chimpanzees used branches weakened by a storm to make a ladder and escape from their enclosure at the Belfast Zoo.
Video filmed Saturday by visitors to the Northern Ireland zoo showed several primates scaling a wall and perching atop it, with one walking down a path outside the enclosure.
Zookeeper Alyn Cairns said trees in the chimps' enclosure had been weakened by recent storms, allowing the animals to break them and fashion a ladder to escape. He told the BBC "they're intelligent primates and know they're not supposed to be out of their enclosure, so got back in themselves."
Two weeks ago a rare red panda escaped from the same zoo when its electric fences failed. The animal was recaptured in the driveway of a nearby house.
Danielle Monaghan, who was at the zoo with her two children, was fearful for her family's safety.
“I was petrified, obviously, having the kids, and I tried not to show fear but inside I was a bit like: what happens if it attacks us or tries to take the kids or runs over?” she told the BBC.
“But we just had to stay calm. It may have been a different story if it had been aggressive but it absolutely wasn’t. It made us feel at ease. We just walked past it and it was absolutely grand.”
They couldn't believe what they were seeing when one of the chimpanzees started to climb out of its enclosure and ended up a foot away from them.