Why Crocodiles Sleep With One Eye Open

Crocodiles sleep with just half the brain at a time, in unihemispheric sleep, said La Trobe University. Hence, they can sleep with one eye open, as well as half the brain open, even as the other eye is shut, and connected to the "sleeping brain".

This makes the crocodile aware of both predators as well as prey, according to HNGN. 

Even as the behaviour has been observed in other birds and aquatic mammals, such as dolphins, the phenomenon is newly discovered in crocodiles.

Research shows that crocodiles tend to sleep with one eye open in the presence of humans and remain focused on any potential threat.

"These findings are really exciting as they are the first of their kind involving crocodilians and may change the way we consider the evolution of sleep," said lead researcher Michael Kelly.

Hence, through this, scientists hope to crack open the secrets behind the effectiveness of sleep in all living beings.

"The value of the research is that we think of our own sleep as 'normal' - a [behavioral] shutdown that is a whole-brain affair," said John Lesku from La Trobe's School of Life Sciences. "And yet, some birds and aquatic mammals sleep unihemispherically with one eye open.  If ultimately crocodilians and other reptiles that have been observed with only one eye closed are likewise sleeping unihemispherically then our whole-brain (or bihemispheric) sleep becomes the evolutionary oddity."

The findings were published in a recent edition of the Journal of Experimental Biology.