There was always that kid who bragged about being "double-jointed" on the playground at school. He'd demonstrate by bending his fingers way back, seemingly past the breaking point, wowing a crowd of normals constrained by their humble human joints. Or maybe he'd even bend his neck to one side and then the other, eliciting a "pop" at each extreme that made you cringe and imagine someone's neck being snapped in a bad kung fu movie. What a show-off, right? Well, even the braggiest of schoolyard braggarts has nothin' on owls, which can rotate their necks 270 degrees in either direction.
Everybody knows the image of the owl with head exaggeratedly cocked to one side, but we never had a good idea of how they could be so bendy without constricting the flow of blood to their brains. Now researchers from John Hopkins have an answer, which they've compiled into a detailed and colorful graphic picked up by Discover Magazine. Handy.
Owls' vertebrae and blood vessels stand out from other birds. They essentially have arterial backup systems, like a connection between the basilar artery artery and the cerebral carotid artery that "provides an additional collateral pathway, assuring constant blood flow to the posterior aspect of the brain." Owls have reservoirs under their jaws that can hold blood and provide fresh oxygen to their brains when their heads are tilted to the extreme and actually cut off blood flow.
But even when owls have some serious tilting action going on in their necks, they can keep pumping blood up to their brains better than most creatures. Researchers found that the diameter of the transverse foramina, which arteries pass through, is 10 times the diameter of the vertebral artery and surrounded by air sacs that cushion the arteries. The graphic also points out that the owl's intermediate carotid arteries are positioned close to the neck's axis of rotation, "decreasing the likelihood of stretching and/or occlusion of the arteries."
Owls' entire bodies are designed around the ability to turn their heads to extreme angles.
In humans, hypermobility, the proper term for being "double-jointed," isn't actually good for our muscles. Standing around popping our necks stretches out the ligaments that support our necks, muscles contract, and we get more and more tense. Owls' entire bodies are designed around the ability to turn their heads to extreme angles, since their forward-facing eyes are fixed in one direction. But they still sort of seem like show-offs.