Question: What creatures stay conscious when they are sleeping?

Mike Ambler answered on 5 Nov 2018:

Hi Nico!

Fantastic question..

First of all, have you ever wondered how you know whether something else is conscious? It’s surprisingly hard to know what it feels like to be in another person (or animal’s head), which makes it quite a tricky thing to investigate.

But, some animals need to stay partly awake at all times in order to survive: whales and dolphins have to go up to the surface of the water to breath even when they are asleep, and what they do is let one half of their brain sleep while the other one stays a bit more awake and controls them going up for breath. Also, migrating birds have to do something similar – they keep flying with one half of their brain asleep and the other half awake, then they switch over! I think there are also some sharks that have to keep swimming to make water flow over their gills (like we breath), and so I think part of their brain stays awake to do this while the rest sleeps.