My grandfather taught me that all living things have a soul. I don't know about plants, but I'm sure about animals. And only loneliness can be more terrible than death for the soul- death during life.
No matter how strong the soul tries to be, she is looking for her own kind, reaching out to them in order to feel herself and the life around her to the fullest.
Maybe life in captivity is not such a terrible sentence when you are not alone. The main thing is that you are there and you can feel the life around you. The memory of ancestors and instincts will remind you of themselves with vivid dreams and something barely perceptible in wakefulness. And it is impossible to get rid of this sadness. But your sadness will be taken away by the souls nearby.