Question: How is it possible that dolphins maintain half of their brain aware during sleeping?

Mike Ambler answered on 6 Nov 2018:

Hi Nora, great question….

I mentioned this in an earlier answer, and it’s great that you’ve asked for more information.

I don’t actually know how it happens, but it is very interesting. Have you ever seen a brain? They have two halves (a left side and a right side), which are pretty much mirror images of each other, and they are connected by bundles of nerves, a bit like telephone wires. These bundles let each side talk to the other. But each side can work pretty well on its own – one side tends to be more involved with things like speaking and understanding language, while the other side tends to be more involved with things like maths and finding our way around the world (like our own internal sat nav or google maps). Intersting things happen if the connections between the two sides get damaged or stop working (have a look at this for more information http://thebrain.mcgill.ca/flash/capsules/experience_bleu06.html).

Anyway to go back to your question, the two halves of the brain can function pretty well on their own (but nor perfectly), so a dolphin can let one half of its brain sleep while the other half carries on working, and then vice versa. Their brains arent’ working like normal, but well enough to make sure they swim to the surface to take a breath! have a lookhere for more info: https://uk.whales.org/faqs/facts-about-whales-and-dolphins/how-do-dolphins-sleep