It's a myth that owls can turn their heads 360 degrees. They can, however, swivel them up to 270 degrees -- and scientists have finally figured out how they do this without cutting off the blood supply to their brain.
First, watch just how dramatic an owl spinning its head can look (N0te: the actual swivel happens at 0:22):
Medical illustrators and neurological imaging experts at Johns Hopkins Medicine have taken what are thought to be the first CT scans and created the first medical illustrations showing several adaptations that allow the owls to turn in such a manner without injury, according to a press release.
(Image: Fabian de Kok-Mercado, Johns Hopkins University School of Medicine, Department of Art as Applied to Medicine)
"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," study senior investigator and interventional neuroradiologist Philippe Gailloud, M.D, said in a statement. "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."
The team studied different species of owls who died of natural causes by using an injectable dye that would show in the birds' blood vessels in X-ray images. They manually turned the owls' heads to conduct observations, and saw that the blood vessels got larger from the base of the head. The researchers pointed out that this is unlike human anatomy where blood vessels get smaller as they become more branched.
They also found the owls' major arteries go through boney holes that are large enough to allow the blood vessel to move around comfortably. The major blood vessels also enter higher up on the neck, which gives them more room.
Here's a look at more of the illustrations. You can see the full image in more detail here. (Image: Fabian de Kok-Mercado, Johns Hopkins University School of Medicine, Department of Art as Applied to Medicine)
"[O]ur 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," Gailloud said. "Extreme manipulations of the human head are really dangerous because we lack so many of the vessel-protecting features seen in owls."
The work won the team first place in the posters and graphics category of the National Science Foundation's 2012 International Science & Engineering Visualization Challenge.
Read more about the details about the adaptations discovered here.
Featured image via Shutterstock.com.