The gorilla had an IQ between 75 and 95.
Koko the Gorilla, who was world-renowned for her ability to communicate with sign language and show empathy, has been found dead at age 46; she died in her sleep at the Gorilla Foundation's preserve in California's Santa Cruz mountains.
"Koko touched the lives of millions as an ambassador for all gorillas and an icon for interspecies communication and empathy," a spokesperson for the organization wrote on their website. "She was beloved and will be deeply missed."
The marvellous ape was said to have an IQ of about 75 to 95; the average human IQ ranges between 90 to 110. Koko was able to sign more than 1,000 words and could understand spoken English.
She was born in the confines of the San Francisco Zoo, and was taught sign language by Dr. Francine "Penny" Patterson back in 1974 as part of an experiment put on by Stanford University.
Koko spent her entire life in captivity, but was able to captivate the hearts of individuals on a global scale. An image of the ape mourning the death of her pet kitten was used as the cover photo for an issue of National Geographic. Throughout her lifespan, Koko adopted many feline creatures, and used sign language in order to give her pets names like All Ball, Lipstick and Smokey.
"Her impact has been profound and what she has taught us about the emotional capacity of gorillas and their cognitive abilities will continue to shape the world," the foundation notes.