How Do Sharks Sleep

Sharks are the terrors of the seas to some but the most graceful and amazing creatures to others. No matter what your personal opinion of sharks is you have to admit that sharks are interesting animals. They can range from 6 inches to 53 feet, live in freezing arctic waters or frequent the warm equatorial seas, viciously attack anything that moves or just open a gaping mouth for the smallest of creatures to enter. Sharks are amazing creatures and are studied constantly across the globe.

Even with the constant study and observation there are still things about the kings of the ocean that we don’t know or argue about. The list of disputed shark facts and theories could go on forever, and this is partially due to the fact that humans have only been whole-heartedly studying sharks for around 40 or 50 years. Before that, studying sharks was left to the adventure seekers and the few marine biologists willing to brave the waters of the world’s oceans.

If you believe the Discovery Channel, the movie Jaws changed all that though. If you watched “How Jaws Changed the World” during Shark Week this year you would have learned that the Steven Spielberg smash not only created an irrational fear of sharks, but it also created a substantial increase the study of marine science across the globe. In essence, a movie designed to instill fear of sharks actually lead to an increased love for the animals.


Learn About Different Types Of Sharks Here!


The Big Question: Do Sharks Sleep?

Despite this drastic increase in the study of sharks and the invention of an entire week dedicated to them on television, there are still things we don’t fully understand about sharks. One of the most widely disputed nuances of sharks is if they sleep or not. That’s right, scientists across the globe have been arguing for the past few decades over if sharks catch some “zzzzz” or not.

The root of the problem stems from how sharks breath. Sharks are intriguing animals in that in order for them to process oxygen, water must continually pass through their gills and into your body. Seeing that sharks don’t have the luxury of fans to blow water into their gills, they must constantly move so that water passes through their gills. At least this is one of the theories.

A problem with this theory arose when marine biologists began to study the Nurse Shark in more detail. When observed in their natural environment Nurse Sharks were seen to remain motionless or “resting” on the bottom of the ocean floor. This initially alarmed scientists until they dug deeper.

Shark Facts to Help Answer the Question

According to the Florida Museum of Natural History; “It was once believed that all sharks had to swim constantly in order to breathe and could not sleep for more than a few minutes at a time. Oxygen-rich water flows through the gills during movement allowing the shark to breathe. While some species of sharks do need to swim constantly, this is not true for all sharks. Some sharks such as the nurse shark have spiracles that force water across their gills allowing for stationary rest.”

In other words certain species of shark actually have evolved a mechanism within their gills that allow them to stop for a few short moments and still be able to breathe. This new discovery has lead to many arguments in that many people now believe that sharks do indeed sleep, but looks can be deceiving.

Defining Sleep is a Struggle of Its Own

For starters, science has not been able to come up with a concrete definition of what exactly “sleep” is. Does sleep need to be defined as a period of what would appear to most as unconsciousness or is it more of a period of time where a creature’s body slows down its processes so that it can rest? Using the first definition very few creatures outside of mammals actually sleep, but with the second definition, almost every animal on the planet can be believed to have periods where they sleep.
When it comes to sharks it really comes down to your stance on the definition of sleeping. It has been surmised in numerous studies that most species of shark actually have periods where they slow down and certain functions in their body slow to a crawl. This can be viewed as a rest-state or a period of sleep depending on your point of view. To others this is not a clear cut sign that sharks sleep or not.

Picking a Side in the Argument

With our current understanding of sharks and a concrete definition of sleep, it is more than difficult to state if sharks do or do not sleep. If a side must be chosen for the purposes of this article, then the author would reside on the side that supports sharks NOT sleeping. This is primarily based on a human perspective of sleeping, which science hasn’t shown that sharks actually have sleep patterns like humans. In the end you must of course choose your own side of the argument.