Koko, the gorilla with a vocabulary of over 1,000 American Sign Language signs, died at a preserve in the Santa Cruz Mountains at age 46.
Born at the San Francisco Zoo on the Fourth of July in 1971, the female western lowland gorilla was chosen as an infant to work with psychologist Francine "Penny" Patterson on a language research project.
After appearing on the cover of National Geographic, Koko became famous for her ability to communicate with humans and convey her emotions using sign language.
She lived in a preserve run by the Redwood City based Gorilla Foundation, a non-profit that relies on "interspecies communication" to help spread a message of conservation.