This is heartbreaking and stupid. Sometimes humans can be incredibly cruel. It's the story about a chimp that was taken from the wild as a baby and raised as a human boy with human parents, wearing clothes and being taught sign language. In the end when the money ran out, they dumped him:
...all the while making it clear he longed for his human family. For a creature who would demand hugs after being disciplined, and bring tissues to his adoptive mother when she cried, relocating to a world of cages and strange, hairy beings was incomprehensible.
There was a children's book all about Nim while he was in New York, basically a photo book, and Nim kept his one copy of this book safe, even though chimps tend to wreck everything. He would bring it down and show the other chimps, then bring it back to his bunk and keep it under his sleeping area so that no one could destroy it. He would just look at pictures of his New York City family, and himself, over and over again
Older chimps taken from the wild surely feel this longing for their natural parents as well, put into cages with strangers and never to see their families again.