Many shark admirers ponder the following question: Do Shark sleep? How do sharks sleep? They don’t sleep.
Sharks do not sense sleep the same way humans do. Some people cannot sleep, and those can never seem to drift off to sleep. Some shark species do cycle through alternate periods of vigilant awake and profound slumber that is analogous to sleep. We are very convinced that sharks do not dream how humans and certain other animals do.
Like all fish, sharks breathe through respiratory structures called gills. All sharks require a continual water flow to pass past their gills to survive physiologically. Some sharks manage this by remaining in motion at all times. Sharks on the move may not sleep at all. Sharks that can stop swimming to rest use specialized machinery known as spiracles to propel oxygen-rich water through their gill system. Shark relatives like rays and skates also breathe through spiracles.
When do sharks go to sleep?
Many sharks that inhabit the pelagic regions of the open ocean swim all the time and do not sleep. However, it’s relatively far from shore and nowhere near the bottom. If they are restrained in anything like a fishing net (which happens all too frequently!), they develop hypoxia, lack of oxygen, and drown. Marine researchers refer to sharks with this survival requirement to swim as obligate ram ventilators. In this context, an example of ram is how sharks “inhale” air through an open mouth and then “ram” it back out through their gills.
Buccal pumpers are sharks that use their cheek muscles to pump water into and out of their gills, which refers to sharks that must move to breathe. Swimming with their mouths open wide allows ram ventilators and buccal pumping sharks to gain more oxygen and energy.
Obligate ram ventilating sharks include:
- Great White shark
- Hammerhead shark
- Sea mammal called the whale shark
- A great white shark is called a mako.
- Megamouth shark
- Thresher shark
Recent studies demonstrate that the spinal cord causes sharks to swim, not the brain. Therefore, certain always-moving sharks may have moments of reduced brain activity during their rest. It is now believed.
Generally, sharks that stay at the bottom of deep and shallow seas can stop moving and remain at rest or near sleep. They can do so on a coral reef or sandy seafloor. The same mechanisms as those used by pelagic sharks are used by bottom-dwelling sharks when they are awake and active. They sink or swim to the bottom where they sleep while breathing via the spiracles behind their eyes when they seek deep rest.
The following are known to sleep while immobile:
- White Tip Reef shark
- A shark from the Caribbean Reef
- Nurse shark
- Wobbegong shark
- Lemon shark
The majority of marine biologists agree that sharks go through cycles of consciousness and unconsciousness.
How do they protect themselves when not awake?
Like dolphins, evidence indicates that sharks may “turn off” one-half of their brain when they fall into a deep resting cycle. Disregard the notion of sleeping half-awake. Half of a shark’s brain is active during a deep rest period, yet both of its eyes are awake at all times!
Sharks don’t close their eyes because they have no eyelids. Instead, they have a translucent “nictating membrane” that covers the eyeball shortly before the shark bites its prey.
So, what do they actually do?
Most sharks spend their time cruising leisurely and eating. Carnivores, sharks eat fish as their primary source of protein. At forty feet long, the huge Whale shark is the world’s largest shark. It feeds on plankton, which is microscopic organisms.
Sharks rarely harm humans. When a shark attack does occur, it is usually a case of mistaken identity. Surfers are more likely to be attacked by sharks because a shark nearby thought they looked like a tasty seal or marine turtle.
Sharks are extraordinary creatures, perfectly equipped to survive. Ancient shark fossils have been found that have been carbon-dated. They show they existed long before the time of the dinosaurs in forms remarkably similar to those of today. Just imagine that. Although the most powerful species on Earth have been wiped off, sharks have survived. It’s amazing that humans have posed the greatest danger to sharks since the dawn of time.
They are a crucial element of the ecosystem.
It is a widely held misconception that sharks are vicious, man-eating creatures. People are a significantly greater threat to shark populations than any ocean-dwelling shark. Humans kill tens of millions of sharks per year, if not hundreds of millions. However, sharks kill just around a dozen people each year. By the time you are finished reading this essay, many more sharks will have died at the hands of humans. So who is the REAL mass killing predator?
The waters wouldn’t last long if all of the sharks in the world disappeared tomorrow. Sharks are a critical part of the food chain and work hard to protect a healthy ocean environment. The more you understand these fascinating aquatic creatures, the less you are inclined to fear them. Also, the more likely you are to recognize their vital role in our existence.
