A long time ago I wrote a short story about a fox who just wanted to sleep. He was living in a sublet, going out of his mind, deprived of sleep. The noise, unending, non stopping, incessant from the elephants living above. It was meant as a parable for the importance of sleep to the human machine.
If you're a wild animal- your cyrcadian rhythm is ordained by the sun coming up and setting. The body doesn't care it's just a screen, generating the light you concentrate on while you work.
How far removed from nature is an animal whose sun sets whenever the animal decides?
Alas the story is on a hard-disk that ceased functioning, so it will likely never be seen again. All I got left is this fox, out to investigate the source of the noises in the dark.