How do giraffes drink without passing out?

With their elongated necks and spindly legs, it’s easy to assume most activities are pretty awkward for a giraffe, so how does it manage to keep itself hydrated without collapsing?

First off, a giraffe’s neck might appear long but it’s actually a lot shorter than its torso and legs combined. Despite their ability to reach food inaccessible to other species, and a talent for long distance vision, giraffes only have seven cervical vertebrae in their necks, each one being up to ten inches long.

Giraffes can’t simply lean over and start gulping down water, as unfortunately they just cannot reach the floor.

Instead, a giraffe will perform an awkward manoeuvre where it splays its front legs out on either side and slowly lowers its mouth to a water source. However, this action puts the creature at great risk of being attacked by a predator from behind. It takes times to get themselves into position ready to drink, and even more time to stand back upright again. Giraffes seem to be aware of this fact and can often be seen deliberating near water sources. They also spend a lot of time scoping out the area for any potential threats and loitering to assess the situation before finally risking a sip.

It takes a lot of time and coordination for a giraffe to reach a water source on the ground.

 

Aside from the risk of predation, having dip the head lower than the heart can also be challenging. If you were to sit with your head between your knees for long enough or even do a hand-stand, I’m sure you would begin to feel light-headed. A human heart only has to pump blood up about a foot, whereas a giraffe’s heart has to pump blood up about seven feet.

Giraffes have the highest blood pressure of all animals at around 280/180. If a human’s blood pressure were to increase that high – it would be a medical emergency. So how do giraffes do it?

Giraffes must splay their front legs in order to bend down and drink.

 

Firstly, they have a large heart. A giraffe’s heart has to overcome gravity by being large enough and strong enough to push blood vigorously enough to reach the head. Giraffes have special valves in the jugular veins, which close when a giraffe bends down to reduce pressure in the brain and stop excess blood flowing into the head, these valves reopen when the giraffe raises its head. Alongside this, they have elastic-walled blood vessels that expand and contract to help control the amount of blood flowing to the brain to help reduce pressure. And lastly, giraffes have a sponge-like structure in their heads to contain any extra blood coming to the brain.

All of these features work together just to allow a giraffe to bend down and take a sip of water. They are fortunate enough to get most of their moisture from the plants they eat, so they only need to drink once every few days!

 

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Photographs: kimvanderwaal, Gusjer