Koko (born July 4, 1971, at San Francisco Zoo) is a Western Lowland Gorilla who, according to Francine ‘Penny’ Patterson, is able to understand more than 1,000 signs based on American Sign Language, and understand approximately 2,000 words of spoken English.

After 40 years, Koko represents a unique experiment in interspecies communication.

…and as for the cat in the main image, although not unique, Koko is one of the few non-humans known to keep pets. She has cared for several cats over the years and Koko’s relationship with All Ball was featured in the 1987 book Koko’s Kitten, which was written by Patterson. In the book, Patterson reported that, in the summer of 1984, Koko asked her for a cat. Koko selected a gray male Manx from a litter of abandoned kittens and named him “All Ball.” This breed is unusual in that it has no tail. Patterson wondered whether that influenced Koko’s choice. Patterson wrote that Koko cared for the kitten as if it were a baby gorilla.

In December of that same year, All Ball escaped from Koko’s cage and was hit and killed by a car. Later, Patterson claimed that when she signed to Koko that All Ball had gone, Koko signed “Bad, sad, bad” and “Frown, cry, frown, sad.” Patterson also reported later hearing Koko making a sound akin to human weeping. Patterson uses this to argue that non-human species can have human-like emotions.

In 1985, Koko was allowed to pick out two new kittens from a litter to be her companions. The animals she chose, later named “Lipstick” and “Smokey,” were also Manxes like All Ball.