Ever feel a little woozy after you pick something up off the floor and stand up again quickly? First the blood rushes to your head as you bend over, and then it suddenly drains away as you straighten. Now imagine you are 16 feet tall, and straightening up quickly is necessary for your safety. Welcome to a giraffe’s world!
We have to wonder why we don’t see giraffes stumbling about, looking like their heads are spinning. Medical scientists studied giraffe blood pressure and circulation to find out why blood doesn’t rush to the brain when a giraffe bends to drink, and why it doesn’t drain away, causing the giraffe to faint, when it lifts its head to a normal position. They’ve discovered that giraffes have valves in the artery and veins of the neck that interrupt blood flow, slowing the rush. This is a very fortunate adaptation, considering a giraffe heart can be two feet long, and pumps 20 gallons of blood a minute. Nobody wants to have to steady themselves to let all that blood settle down when there’s a hungry lion in the neighborhood!