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We all know what it feels like when we have not had enough sleep. You might feel tired, have trouble concentrating, or even be grumpy and irritable. Despite it being such an important part of our daily lives, sleep still remains a bit of a mystery! To help answer the question of why we sleep, scientists have started researching sleep in other animals. This can help us understand how and why sleep evolved.

Sharks are hundreds of millions of years old. In fact, they are the oldest living group of jawed vertebrates! Because of this, we think they could help unlock important information about the evolution of sleep. So far, only one study has focused on sleep in sharks. We wanted to change this!

We studied the metabolic rate and behavior of draughtsboard sharks (Cephaloscyllium isabellum) over a 24-hour period. Our results show that when sharks sleep, they typically have a flat body posture and a reduced metabolic rate. Our study supports the hypothesis that the conservation of energy is a core function of sleep. It also provides insight into its evolution.


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