TIL: Why Animals Sleep So Much

I love animals - I have had many pets throughout my life.

When looking at my cat today I wondered why do some animals seem to sleep all the time?

I know that this doesn't apply to all animals, but I have noticed a lot of them do sleep all the time they can.

I know that human beings generally sleep about 6 - 8 hours, and I thinking the reason we do mostly is because we have to work to survive. 

So, I did a little digging and found a good list of theories:

Sleeping Theories

• One of the theories is that sleeping makes you less apparent to your predator. It is easier to find a dark spot, curl up and make the least possible noise and therefore less of a target for becoming prey. [Source]
• Another is energy conservation. If you aren’t doing anything, why waste it being awake. You might need that energy later, so you might as well take a nap instead! [Source]
• Other theories include brain plasticity (where the brain reorganizes itself and allows the body to function at optimal levels) and, of course, body restoration. [Source]
• A cat or dog or even other smaller mammals have much higher metabolic rates than we do, so they need more sleep to keep their bodies functioning at the correct level. Giraffes sleep approximately 20 minutes per day. High on the predatory list, all they need is a quick nap to keep going all day. [Source]

I think it might be a combination of these theories, if not all for some animals... but not for all

Image sources: 1 2 3