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There was one gorilla whose long-term mate and friend died in the zoo, and he first tried to revive her, even bringing her favorite food to her and putting it in her hand and poking her, and then at some point he seemed to come to a really stunning realization that his friend was not going to move. I don’t know if that’s a concept of death, but his behavior changed and he let out a very agonizing wail and stopped trying to revive her. Clearly something cognitive and emotional happened to him at that moment.