How Do Owls Turn Their Heads So Far Without Dying of Stroke?
The fact that owls can turn their heads incredibly far is nothing new. Scientists have known for a while that owls have extra vertebrae in their necks that give them a range of movement far beyond what's possible for humans. But until recently, scientists didn't know how the delicate arteries in the birds' necks could keep up. It's common for humans to damage their arteries from extreme neck movements during accidents, causing blood clots and stroke. So why aren't owls routinely dropping dead from their incredible head turns? According to research out of Johns Hopkins University, several adaptations make this possible: for one, an owl's vertebral artery travels through a hole in the vertebrae that is 10 times larger than it needs to be, giving it a lot of wiggle room as the spine twists. There are also extra blood vessels connecting that artery to a second major artery so even if one of them is blocked, the other can keep delivering blood to the brain. And as a final failsafe, several arteries at the base of the head enlarge to collect blood in reservoirs. Scientists think this could be a way for an owl's brain to get a fresh blood supply when head turns might block off the usual sources.
Key Facts In This Video
Owls have twice as many vertebrae in their necks as we do. (1:11)
The canal in owls' vertebrae that houses the ascending vertebral artery is 10 times larger than the artery itself, giving it a lot of room to move. (2:04)
Blood pools in arteries at the base of the head, possibly to help provide a fresh source of blood to the brain when regular blood flow is restricted during an extreme head turn. (2:51)