Sheep Save Sweat by Cooling Their Brains

Looks like camels are not the only animals that can save the water they drink throughout the day. New research has found that sheep, who understandably become overheated under their thick sweaters of wool, can save the water they would otherwise sweat out by literally cooling their brains.

That's at least according to a new study recently published in the journal PLOS One, which details how the animals can save up to a stunning 80 percent of their daily water intake by using this system.

So how does it work? Past physiological studies have shown that sheep keep cool blood flowing into their brain using something called a carotid rete.

Found at the base of the skull, this structure contains arteries with blood flowing towards the brain that divide into many fine vessels. Heat is transferred out of these fine arteries into other nearby vessels which contain blood already cooled by the simple evaporation that occurs in a sheep's nose. This is not unlike how we can tell is a dog is feeling unwell - with poor body temperature regulation - when his nose is not wet.

The common wisdom has been that this cooling system is used to protect the sheep's brain from overheating, but a bizarre study of South African wildebeest in the 1990s revealed something that didn't match up. (Scroll to read on...)

According to ABC Science, researchers actually chased the poor animals in helicopters while systems attached to their skulls monitored temperature and blood flow in real time. And while this may seem like a LOT of effort for a simple project, they did find that when the wildbeests' brains were at their hottest, the cooling mechanism wasn't functioning, throwing the overheat theory completely out the window.

That's when researcher Shane Maloney from the University of Western Australia and his colleagues stepped in, launching a bit more practical of a study to test if this brain cooling had more to do with water retention.

Maloney's team found nine sheep who all naturally varied in how much time they spent with the brain cooling function on during the day, and compared their differences in a temperature controlled room. On the last five days of the study, the sheep were deprived of water. That may sound cruel, but it's important to point out that sheep can go thirsty for at least seven days without much difficulty.

They found that the longer the sheep went without water, the longer their brain cooling stayed active. This suggests that there is indeed a direct link between a need to save water and the mechanism.

The researchers additionally found some evidence that the more sheep become stressed, the less efficient this brain cooling is, as resources needed to activate it are used to activate fight or flight responses instead. This could explain why the helicopter fleeing wildebeest weren't able to cool off.

However, much more work will need to be done to verify this theory.

So what's the point of all this? The end game, according to Maloney's team, is to identify genes that encode for efficient cooling - something that could allow animal experts to breed sheep that can be raised in even hotter climes.

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