The chimpanzee was active on his last day, a spokesman at the zoo in Portland told The Oregonian. Bill LaMarche said that Thursday morning Charlie greeted the keepers with his usual gusto and climbed on the structure provided for him.
At about 3 p.m., keepers heard commotion and saw one of the chimpanzees fall. By the time they got the four females who shared the exhibit with Charlie out of the way, he was dead.
Charlie was 39 when he died, late middle age for a chimpanzee. He was brought to Portland as a youngster by Edward Miller, a contractor from Africa who bought the baby to keep him from becoming bush meat. Miller gave him to the zoo in 1972.
Dave Thomas, 60, the zoo's senior primate keeper, began working with Charlie as a volunteer in the early 1970s.
"I thought I'd be leaving him, not him leaving me," Thomas said. "This is an end of an era."
A necropsy determined Charlie was most likely killed by a heart attack or stroke.