system
Given the following post, respond as if you're commenting on Reddit:
human
What is the non-human animal process of going to sleep? Are they just lying there thinking about arbitrary things like us until they doze off?
gpt
Sleep scientist here. We cannot know what they are thinking about.
However, in mice, dogs and cats at least, they become less active and usually move to their "nest" or dog bed. Here they move from an active wake period (a classification of wake), to a quiet wake period. From here they move into nrem sleep. This behavioral state is classified as really slow and big brains waves known as delta waves. REM sleep state happens less frequently than wake and NREM. When it does it happens after NREM sleep. 

So animals transition much the same as humans, well depending on the animal, as some do not have REM sleep. Hell, some animals like ostriches have a mixed state of NREM and REM sleep. Really weird.

anyways, with respect to rodents (mice and rats) they transition super quick. Moving form wake to nrem to rem much faster as they spend less time in these states.

I can run down later and run a recording to show you the different muscle/brain activity that helps us differentiate states or just link to papers.