How Do Owls Turn Their Heads?

An interesting fact about owls: they cannot move their eyes! In order to follow the movements of their prey, they have to turn their heads. Owls can turn their heads up to 270 degrees, or three-quarters of the way around. If we did that we'd rupture blood vessels and cut off the blood supply to our brains. So how do owls do it?

Researchers at Johns Hopkins University, led by medical illustrator Fabian de Kok-Mercado, M.A., found major biological adaptations in owls' bones and arteries that prevent injury when they rotate their heads. 

The team studied the heads and necks of Snowy, Barred and Great Horned Owls after they'd died from natural causes. They discovered that one of the major arteries nourishing the brain passes through bony holes in the vertebrae (neck bones). The hollow cavities are about 10 times larger across than the artery traveling through them. The researchers say that this extra space allows the artery to move when it's twisted. Twelve of the 14 vertebrae in the owl's neck were found to have this adaptation.

Among the team's other findings: small vessel connections between the carotid and vertebral arteries that allow blood to be exchanged between them. We humans don't have these connections. The researchers say they allow for uninterrupted blood flow to the brain even if one route is blocked when the neck rotates.

No word on whether your high school math teacher had any of these adaptations. Better to assume she simply had eyes in the back of her head.

Want to hear more about owls and their amazing necks? We did a Science Corner piece about it on the radio show of December 8, 2013. Click here to listen!