Night-hunting owls can rotate their heads 270 degrees in either direction — that’s nearly a complete rotation. If humans did that, our heads would probably fall off — or, at least, we’d cut off the blood supply to our brains and crush blood vessels in our necks and heads. (Hence whiplash and terrifying chiropractic accidents.) But the exact mechanism for owls’ head rotations has been a mystery — until now.
It took a mix of old-fashioned skills (medical illustration) and new-fangled technologies (neurological imaging) for Johns Hopkins experts to figure out how those rotational head movements work. The team took dead (of natural causes!) owls and injected dye in their blood vessels. They then manually turned the owls’ heads to see what happened. According to Johns Hopkins Medicine, “Blood vessels at the base of the head, just under the jaw bone, kept getting larger and larger, as more of the dye entered, and before the fluid pooled in reservoirs. This contrasted starkly with human anatomical ability, where arteries generally tend to get smaller and smaller, and do not balloon as they branch out.” In other words, these blood vessels allow the birds to pool the blood that flows to their brains and eyes, even when their heads turn in such a way to compress these arteries. The owls also had holes surrounding their vertebrae that created cushioning air pockets that enabled arteries to twist more successfully than their human counterparts.
“Until now, brain imaging specialists like me who deal with human injuries caused by trauma to arteries in the head and neck have always been puzzled as to why rapid, twisting head movements did not leave thousands of owls lying dead on the forest floor from stroke,” said the study’s senior investigator, Philippe Gailloud. It took the expert input of artist-scientists from the school’s graduate program in Medical and Biological Illustration to finally solve the mystery. And whereas “extreme head rotations” in humans “are really dangerous because we lack so many of the vessel-protecting features seen in owls,” Gailloud said, owls can manage just fine. Superb indeed.