Chimpanzees have used a branch to escape from their enclosure at Belfast zoo in the second breach by animals in recent weeks.
They took advantage of damage caused by stormy weather to stage a breakout, which visitors caught on film.
It comes after a red panda cub called Amber was found in a garden less than a mile from the zoo after it escaped from its enclosure last month.
The latest bid for freedom was made by chimps who used a branch as a makeshift ladder and scaled high walls surrounding their pen on Saturday.
Visitors described seeing one of the escapees emerge from the bushes on to a path while others were sitting on top of their enclosure wall.
In footage posted on social media, a child can be heard exclaiming: “Don’t escape, you bad little gorilla.”
Zookeeper Alyn Cairns said trees in the enclosure had been weakened by the storms, allowing the chimps to break them and use them as 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.”
'They know they're not supposed to be out of their enclosure?' rolls on floor
A spokesperson for Belfast city council, which runs the zoo, said one chimpanzee left its enclosure for a short time.
“Zookeepers were present as the chimpanzee quickly returned from an adjacent wall to the rest of the group inside the enclosure,” it said.