Is it true sharks never sleep?

The idea that sharks never sleep is not true. While it is true that some shark species can be found actively swimming and hunting at all hours of the day and night, all sharks do in fact sleep.

Sleep in sharks takes different forms depending on the species. Some sharks, like the whale shark and basking shark, practice a form of intermittent sleep where they alternate between brief periods of rest and activity. During these rest periods, these sharks may remain motionless in the water or swim very slowly with their eyes half-closed.

Other shark species, like the dogfish shark, are known to go into a deeper sleep state where they lie still on the ocean floor and are less responsive to external stimuli. These sleep periods can last for several hours and are typically taken at night.

Additionally, some shark species have been found to enter a unique sleep state called "REM sleep" which is characterized by rapid eye movement and brain activity patterns similar to those observed during sleep in other animals.

Researchers are still actively studying the sleep behavior of sharks, and further research is needed to fully understand the patterns and variations of sleep among different shark species.