Why doesn't sharks sleep??

Question

I read a book about sharks..And it,it said that sharks doesn't sleep..Why??And is this true??

Answer 1

Having watched smallish sharks in tanks, I know they don't need to keep swimming to breathe, they will most often just lurk at the bottom in a heap. Whether they actually sleep the way we do I don't know, perhaps they do as whales do, a whale biologist told me whales put half of their brain to sleep at a time and never go completely to sleep, so perhaps fish do this too. Fish don't tend to have eyelids, so how would you know whether they were asleep or not?

Answer 2

A shark can sleep in a standstill position. They simply rest on the bottom at the mouth of a river, or where there's a current. The current moves the water through the gills and provides the shark with oxygen, so the shark can rest and breathe at the same time!

Answer 3

Actually, this question has caused a big debate among scientists. It was commonly believed that all sharks need to constantly swim in order to breathe (Talk about sink or swim!) The movement allows a continuous flow of oxygen-rich water through their gills. It's true that many sharks need to be permanently on the go, but that doesn't mean they can't rest at the same time.

It's just that sharks don't sleep the way you or I do. Sharks can't exactly snooze the night away in a bed or nest, but they do slow their brain functions down and just chill. Scientists describe this fishy state as kind of like daydreaming. It's also been discovered that some species, like nurse sharks, have openings behind their eyes—these are called spiracles—that force water through their gills, allowing them to stay still and hang out in one place, such as a cave.

Answer 4

Sharks do sleep, although they have no eyelids so it may not appear as though they are. The reason that (most) sharks never stop moving is because the forward motion pushes water through their gills allowing them to 'breathe'. If a shark were to become motionless, they would suffocate / drown. Although it should be noted that this is not the case for all species of shark.

Answer 5

It depends what you mean by sleep. When humans sleep we are not conscious of what is going on around us, we kind of shut-down for a while and are not able to walk around unless we happen to be sleep-walking. Sharks rest in a different way. They can rest part of their brain while still swimming along, semi-aware of what's around them. Sharks that are able to stop swimming will settle on the seabed, and species like the British Bullhuss shark actually close their eyes - so they appear to sleep like we do. In our aquarium I have seen two Sandtiger sharks bump into each other nose-to-nose. They were so startled, they both took off at great speed in opposite directions. This suggested to me that they were dozing on the move and not paying full attention to where they were going, but I have never seen them bump into the sides of the tank when snoozing, so they normally seem to have an idea of where they are. A lot of research has been done on sleep in humans, and many mysteries still surround sleep and its importance to healthy living, but conducting similar research on sharks is almost impossible for practical reasons, we have a lot to learn about sleep and its purpose in fish and other animals.

Answer 6

Sharks can not sleep as we do because if they stop moving, they die. They cant breath in air like we do. Their gills work by moving water through them, and this gives the appearance that they never rest, or sleep.

Answer 7

many animals (probably most) don't need to sleep: what for? to rest their brain ? Anyway, if you sleep you lose conscience, and for an animal like a shark that needs to keep swimming to breathe, it's a problem....

Answer 8

sharks cant stay still as they will drown, but there are cases of them being found in the deepest depths of the sea in caves asleep not moving at all but still alive

Answer 9

they don't sleep. But the stay in one spot for three days, and they they eat.

Answer 10

because they tweek