Another picture of Koko and favourite pet cat.
Koko was devastated when the cat died, and it took a long time to draw Koko out of depression.
All primates express emotions, but because of her command of sign language, Koko can convey to us feelings that her wild counterparts cannot," explains Dr. Francine (Penny) Patterson, who heads the Gorilla Foundation and has been working with Koko and teaching her sign language since 1972.
http://www.pbs.org/wnet/nature/koko/