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.