Crocodiles Sleep With One Eye Open At A Time – Always Awake

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Crocs Rest One Side Of The Brain At A Time How Can They Do This?

Crocodiles are now on a list of Birds and mammals that sleep with one eye open. They do this probably by resting one  hemisphere of their brain at a time leaving the other side completely alert to see prey or danger. Crocodiles are creatures we would try to avoid in the wild as they would see us as prey especially if we were swimming near them. I don’t care whether they have one eye open or not I wouldn’t go near them in the first place!

Enjoy the article and leave a comment about how you may handle a croc situation?

Writing in the Journal of Experimental Biology, the researchers say the crocs are probably sleeping with one brain hemisphere at a time, leaving one half of the brain active and on the lookout.

Consistent with this idea, the crocs in the study were more likely to leave one eye open in the presence of a human.

They also kept that single eye trained directly on the interloper, said senior author John Lesku.

“They definitely monitored the human when they were in the room. But even after the human left the room, the animal still kept its open eye… directed towards the location where the human had been – suggesting that they were keeping an eye out for potential threats.”

The experiments were done in an aquarium lined with infrared cameras, to monitor juvenile crocodiles day and night.

“These animals are not particularly amenable to handling; they are a little snippy. So we had to limit all of our work to juvenile crocodiles, about 40-50cm long,” said Dr Lesku, from La Trobe University in Melbourne.

As well as placing a human in the room for certain periods, the team tested the effect of having other young crocs around. Sure enough, these also tended to attract the gaze of any reptiles dozing with only one eye.

This matches what is known of “unihemispheric sleep” in aquatic mammals, such as walruses and dolphins, which seem to use one eye to make sure they stick together in a group.

By contrast, birds use this strategy to watch out for predators. “In threatening situations, birds will increase their use of unihemispheric sleep and maintain their open eye on any potential threat,” Dr Lesku explained.

“It seems to be a bit of both, in the case of these juvenile saltwater crocodiles.”

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“To me, the most exciting thing about these results is they provide some evidence to think that the way we sleep might be novel, in an evolutionary sense,” Dr Lesku said.

Half-brain sleeping, he explained, may have evolved in a shared ancestor of reptiles and birds, and separately in the aquatic mammals – or perhaps in an even more distant ancestor, shared by birds, reptiles and mammals, before ancient land mammals somehow lost the knack.

Check the video below for more info on Unihemispheric sleeping:

 

 

 

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