sort by best latest
they sleep in nests so they have nowhere to fall.
You can help the HubPages community highlight top quality content by ranking this answer up or down.
That's a very good question. I suppose it's the same answer as the reason why we do not fall out of bed when we are asleep. Our muscles learn to move us only within the safe region.
Copyright © 2017 HubPages Inc. and respective owners. Other product and company names shown may be trademarks of their respective owners. HubPages® is a registered Service Mark of HubPages, Inc. HubPages and Hubbers (authors) may earn revenue on this page based on affiliate relationships and advertisements with partners including Amazon, Google, and others.
Copyright © 2017 HubPages Inc. and respective owners.