How the Owl Rotates its Head
Ever wonder how an owl rotates its neck without injury when you need a neck message after getting your hair shampooed at the salon? A team of researchers at Johns Hopkins set out to investigate how a night-hunting owl can rotate its head by 270 degrees in either direction without causing damage to blood vessels.
Using angiography, CT scans, and medical illustrations to analyze owl anatomy, the team found four major biological adaptions that prevent injury from head rotation. These adaptions are in the bone structure and vascular network which support the top-heavy head of the owl.
Researchers injected dye into the owls’ arteries, mimicking blood flow, then manually turned the animals’ heads. Blood vessels at the base of the head, just under the jaw bone, kept getting larger and larger as more dye entered, and before the fluid pooled in reservoirs. Researchers say this allows owls’ blood to meet the energy needs of their large brains and eyes while they rotate their heads. The supporting vascular network helps minimize interruption of blood flow.
In humans, arteries get smaller and smaller and do not balloon as they branch out. Sudden gyrations of the human neck and head, like in a case of whiplash, can cause blood vessel linings to stretch and tear. This can lead to blood clots that can eventually break off and lead to embolism or stroke.
Owls used in the study had died due to natural causes.
“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,” says study senior investigator Philippe Gailloud, M.D. “The carotid and vertebral arteries in the neck of most animals — including owls and humans — are very fragile and highly susceptible to even minor tears of the vessel lining.” Gailloud is an interventional neuroradiologist and an associate professor in the Russell H. Morgan Department of Radiology at the Johns Hopkins University School of Medicine.
“Our new study results show precisely what morphological adaptations are needed to handle such head gyrations and why humans are so vulnerable to osteopathic injury from chiropractic therapy. Extreme manipulations of the human head are really dangerous because we lack so many of the vessel-protecting features seen in owls,” says Gailloud.
The team was led by medical illustrator Fabian de Kok-Mercado, M.A., a recent graduate student in the Department of Art as Applied to Medicine. Other Hopkins researchers included Michael Habib, Ph.D., Tim Phelps, M.A., and Lydia Gregg, M.A. Details of the study are published in the journal Science.
With the mystery of the owl solved, the researchers plan to study the head rotation of the hawk.
Main post photo copyright: photoXpress.com, Photographer: Kelvin Callear