Seven chimpanzees used an improvised ladder from a tree to scale a wall and briefly escape their enclosure at the Kansas City Zoo on Thursday, a zoo official said.
One of the chimps apparently pulled a log or a branch and leaned it against the wall of the enclosure, giving the primates a leg-up to the top, zoo director Randy Wisthoff said.
The animals did not have any contact with zoo visitors, as they escaped into an area reserved for zookeepers, he added. There are 12 chimps in total at the zoo, which was closed after the incident.
"We had a ringleader," Wisthoff said. "He got up on the log and got some others to join him."
Using food to entice them, the zookeepers herded the wayward chimps back into an indoor enclosure. The chimps were on the loose for around an hour.
Wisthoff said zoo staff regularly checks trees in the area of the chimpanzees for fallen limbs but in this case a chimp apparently pulled a log or large limb out of a tree.