Credit: YouTube, San Francisco Zoo Koko the gorilla, famous for learning approximately 2,000 words of sign language at the San Francisco Zoo, was given a tiny kitten to care for after she became unsatisfied with her stuffed animals. In an episode that surprised biologists and made international news, Koko cared for the kitten, named "All Ball," as if it were her own baby, even trying to nurse him.
Even more remarkable -- when All Ball escaped from Koko's enclosure and was killed by a car, Koko was devastated. When her handler signed her the news of All Ball's death, Koko reacted by signing the words, "bad, sad, bad, frown, cry-frown, sad," and later mourned in her cage by wailing and bellowing.
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