Posted by Elizabeth Bacher, Communications Leo, with Yola and Nadiri in the background, 2016 photo by Jeremy Dwyer-Lindgren, Woodland Park Zoo. Update on Leo’s passing We’d like to share preliminary necropsy (animal autopsy) findings with you regarding our 40-year-old male gorilla, Leo, who passed away on the evening of March 29 after a brief illness. The most significant post-mortem findings indicate the upper middle-age gorilla died from an aortic aneurysm—the internal rupture of the wall of the ascending aorta, the major artery exiting the heart. “The aortic dissection was extensive, extending into the descending aorta, down as far as the lower back region of Leo,” says Dr. Darin Collins, Woodland Park Zoo’s director of animal health. Heart disease emerged as a disease of concern and a major cause of death among all four great apes (gorillas, orangutans, chimpanzees and bonobos) in the early 1990s. In 1991, Woodland Park Zoo lost a male gorilla in his ‘20s due t...