Koko, the gorilla who became famous for learning sign language, has died in the United States. The California-based Gorilla Foundation that kept and studied Koko announced that she had passed away in her sleep on Tuesday. She was 46 years old. “Koko touched the lives of millions as an ambassador for all gorillas and an icon for interspecies communication and empathy,” the foundation said in a statement. “She was beloved and will be deeply missed.” Koko was a western lowland gorilla born on July 4, 1971 at the San Francisco Zoo. The very next year, Koko began working with Dr. Francine Patterson, who taught her American Sign Language. Her keepers said Koko also understood some spoken English.