Sharks sleep with eyes wide open

New Zealand and Australian researchers studied seven draughtsboard sharks from the Hauraki Gulf, off Auckland, New Zealand to explore how and why the animals sleep.

The sharks could sleep with their eyes open and, in common with other animals, sleep was associated with lying flat and a lowered metabolic rate, they wrote in the journal Biology Letters.The draughtsboard shark – sometimes called the “carpet shark” – can stay stationary, resting on the sea floor, unlike sharks which must swim constantly to stay alive.

As in humans, sleep is a method for conserving energy, it seems. The study was the first physiological evidence of sleep in sharks.