There's a very touching video from last year that's making the rounds now. It's a terminally ill chimpanzee at a zoo in the Netherlands who's refusing to eat or drink, and is clearly giving up on life . . . until she recognizes a caregiver she's known since 1972.
She strokes his hair and head, and even gives him a hug. Sadly, she passed away a week later.
She recognizes him at 0:49, and brings him in for the hug at 1:42. Here's a great story about her