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10th Mar 2022

Scientist finally crack mystery of if sharks can sleep

Charlie Herbert

Scientists establish whether sharks sleep

It’s the first study to try and scientifically establish if sharks actually sleep or not

After years of research and studies, a group of scientists from Melbourne has determined whether sharks sleep or not.

Dr Michael Kelly and colleagues at Melbourne’s La Trobe University have made a world-first discovery by establishing that at least one species of shark regularly enjoys a nap.

The study found that Draughtsboard sharks, also known as carpet sharks, even adopt a sleeping position when they get some shuteye, lying flat on the sea bed.

Although there had been anecdotal evidence that sharks do in fact sleep, this had never been scientifically researched before.

The scientists monitored seven draughtsboard sharks over a 24-hour period and found that the sharks’ metabolism – measured through oxygen consumption – dropped during periods of inactivity longer than five minutes.

“Not only do sleeping sharks have reduced responsiveness to stimulation, they also have lower metabolic rate,” Dr Kelly and his team write in the study.

The sharks sometimes slept with their eyes shut, but this was concluded to be a result of the light levels as opposed to how deep their sleep was as it happened most often during the day.

The study concludes: “Future research should focus on other physiological indicators of sleep, such as changes in brain activity, for a more complete portrait of sleep in these vertebrates.”

The findings aren’t just significant for the shark world though, as they may help explain the wider mystery around why it is animals and humans need to sleep, the New Daily reports.

Dr Kelly explained: “We still haven’t gotten our heads around why the hell it is that we spend one-third of our lives in this weird state, where we are just kind of dead, kind of unconscious.

“We know it clears brain waste, and it helps synaptic connections. But why are we tired? And why do you have to go into this weird state?

“We actually don’t know whether there’s one all-encompassing reason that all animals sleep. But the weird thing is every animal we’ve ever studied so far sleeps and it seems to have persisted across all of evolutionary time.”

Dr Kelly reckons that the findings are likely to apply to all sharks because of this, telling IFL Science: “If we find that there are sharks out there that don’t sleep, then they would be the first animals that we would have ever found to not require sleep.

“For this reason, I believe we will find in time that all species we investigate sleep. The question then becomes: do they all sleep in the same way?”

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