Why do some animals stand up to sleep when they could lie down?

Question

I know horses and cows do. Is it because it would be hard for them to get up if there was a predator near by?

Answer 1

That's part of the reason. But, maybe you've noticed that foals and calves will lie down to sleep. The main problem is that horses and cows are so heavy, that if they lay on themselves to sleep, they will squash their organs. Not enough so that they would die, but it makes things uncomfortble--especially breathing-- and they just know not to. Sometimes you'll see horse or cow laying on its side, but only for a short while; they wouldn't spend too much time on their sides.
Also, although it may seem tiring to stand up while sleeping, it's not. Horses' legs "lock" when they are asleep. This allows their muscles to relax, even though the horse is standing up. It's not as if they are actually standing up, their muscles are all relaxed, and they aren't actually *doing* anything to keep themselves up. So it's like they're asleep, totally relaxed, only standing up, so that their insides aren't squashed.
Does that make sense?

Answer 2

The animals which sleep standing up are all grazers, and the reason they sleep standing up has a lot to do with simple anatomy. Grazing quadrupeds do not have a full diaphragm like we do, that separates their guts entirely from their lungs -- and they have an awful lot of gut, because you need that length of gut to break down the insoluble cellulose in what they eat. So this gigantic bag of guts just kind of hangs there inside the skin, protected by the ribs. Also, in many animals the lungs are attached directly to the ribs and breathing *must* involve motion of the ribs. Now, when the animal lies down, this compresses everything: the ribs get squished in along where they lie, and the guts get squished up inside them, and the guts tend to squish up around the other organs -- including the lungs, which can't move as much as normal anyway and which also put further pressure on the heart. The smaller the animal is, the less this is a problem; the less overall weight and compression there is. This is why calves and foals are often to be found lying down, where adult horses and cattle aren't. However, many "medium sized" grazers, like cattle, *can* lie down if they want to -- it is just not comfortable, and as several other people have pointed out here, there are issues of leg length and the time it would take for them to get up if they were attacked by a predator, as well, so they only lie down if they are ill, extremely tired, and/or feeling perfectly safe. However when you get to the very large animals, like elephants, it becomes even more of a problem. It goes far beyond awkwardness -- an adult elephant will actually die if it lies down for more than a few hours, as the weight of the gut pressing up against the lungs eventually puts too much strain on them and they smother.

Answer 3

Horse, cow's, and other herbivore herd animals, do not requir the amount of sleep predator animals do. In a 24 hour period, a normal horse will sleep for about 30-45 minutes, and none of this is taken more than a few minutes at a time. The predator issue is a point, however the dietary intake needs to be consumed almost constently to supply the basic nutrition levels needed. Same with all grazing animals. Cows can be a little more at ease,because they regurgitate cud, that still needs to be processed.

Almost all predators require longer periods of rest, to process fuels, and allow our metabolism to recharge.

Hope that answers your question.

Answer 4

Good guess, you're right :) If a predator were to attack a herd at night while most of the animals are sleeping, it would be hard for all of them to get up and run before the predator could get his claws into them. When they feel safe and when they want a really good sleep, though, they'll lie down.

Answer 5

A horses knees lock to give them the ability to sleep standing up. One reason is for predators but horses do lay down to rest as well but they shouldnt stay down for long periods of time since its too hard on the heart and circulatory system.

Answer 6

cows lie down sitting sortta upright on their chests with their feet tucked neatly under them (like a cat before a fire) to sleep. It is correct they can't BREATH lying on thier sides. and they sleep in short dozing catnaps least a lion sneak up on them.

Answer 7

The larger animals have a more difficult time breathing while lying down. They genetically are programmed to know that if they sleep deeply they could suffocate.

Answer 8

That is one reason, although they do lay down occasionally, but not for long. This is because sometimes large animals can have difficulty breathing if they are laid down for too long because their own weight can crush their lungs.

Answer 9

Alot of the time the ground is nasty. Give them a stall with piles of straw on the floor and they enjoy laying down.

Answer 10

Why do U lay down when u sleep?
U could always stand up!