Koko, a gorilla known for having mastered sign language, has died.
The gorilla was 46 and died in her sleep, The Gorilla Foundation said in a statement Wednesday.
"Koko touched the lives of millions as an ambassador for all gorillas and an icon for interspecies communication and empathy. She was beloved and will be deeply missed," the statement said.
Koko, a western lowland gorilla, was born at the San Francisco Zoo. She has been featured in documentaries and appeared on the cover of National Geographic.
Notably, Koko also formed a relationship with a kitten. The pair inspired a book called Koko's Kitten.