Owls don"t require eyes in the back of your heads to see what"s behind lock — they have the right to just swivel their heads every the way around. In fact, plenty of owl species, such as the prohibition owl, can rotate your heads 270 degrees in every direction, which method they can look come the left through rotating all the way to the right, or angry versa.

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But just how do they do it without severing your arteries or avoiding blood from reaching the brain? one illustrator and a medical professional at the Johns Hopkins University institution of medicine teamed up to uncover out.

"Until now, mind imaging specialists like me who deal with human injuries caused by trauma come arteries in the head and neck have always been puzzled as to why rapid, twisting head activities did not leave countless owls lied dead on the forest floor native stroke," said study writer Dr. Philippe Gailloud, in a statement from the university.

If people tried to rotate our heads so promptly or far, we"d tear the lining of ours arteries, i m sorry would cause clots to kind and bring about a stroke (besides likewise breaking our necks), the added. "The carotid and vertebral arteries in the neck of most animals — including owls and also humans — are an extremely fragile and also highly prone to even minor tears that the courage lining."

Looking within owls

To obtain a glimpse of the owl"s blood vessels when their necks to be turning, the duo injected dye right into the blood vessels of a dozen dead owls and used a CT scan to visualize the shimmering liquid spreading transparent the birds" arteries favor blood, stated Fabian de Kok-Mercado, who performed the job-related while obtaining a master"s in clinical illustration at Johns Hopkins. (He is currently an illustrator in ~ the Howard Hughes clinical Institute in Chevy Chase, Md.) The researchers then twisted the dead owls" top to watch what happened.

After producing the CT scan images, the researchers injected a plastic-like substance into the veins that dead snowy, barred and an excellent horned owls and dissected the animals, illustration the routes and locations of the vessels.


Fabian de Kok-Mercado (left) and also Dr. Philippe Gailloud provide a CT scan to a dead owl come learn exactly how its blood vessels resist the rapid, up-to-270-degree turns their heads make. (Image credit: Fabian de Kok-Mercado and Dr. Philippe Gailloud)

They discovered a variety of previously undiscovered and also unique traits, de Kok-Mercado told OurAmazingPlanet. Because that one, the owls" neck bones, or vertebrae, contain feet that room much larger than those found in other birds or humans. In humans, the hole in the vertebra is around the same size together the artery, however in owls the feet is around 10 times bigger than the artery, follow to the study, published today (Jan. 31) in the newspaper Science. These holes, or canals, likely organize air sacks intended to cushion the twisting motion of the head, de Kok-Mercado said.

"We likewise noticed appropriate away the these canals were lacking in the bottom 2 vertebra of the neck," de Kok-Mercado said. This offers the cord-like vessels some slack when the bird twisted its head.

The huge holes and also "slack" in ~ the bottom of the neck aid explain why the vessels don"t break. Yet they don"t define why the it is provided of blood isn"t cut off as soon as an owl turns its head — v so lot twisting, the vessels are bound to end up being partially blocked.

Blood come the brain

The team noticed the the vertebral artery enlarges slightly together it viewpoints the brain, which is unusual and not viewed in many other animals (like the trunk of a tree, vessels generally gain smaller as they gain farther from the heart). The authors think that these enlarged locations may function as reservoirs in i beg your pardon blood can pool, so that the brain has extra blood to job-related with as the head swivels around, de Kok-Mercado said.

The blood vessels close to the brain are additionally highly connected. A vessel called the patent trigeminal artery connect the front and also the ago of the owl"s brain, which helps supply the organ with as lot blood as possible.

Why execute owls must crane your necks come such an extreme degree? It"s since their eyes are tubular, built nearly like telescopes, providing them amazing vision, de Kok-Mercado said. However unlike humans, that have approximately spherical eyes, owls cannot relocate them around easily, so they have to rotate your heads.

The finding is just one more example of just how the birds room perfectly adjusted to fit their environment, permitting them to see regardless of having relatively fixed eyes.

"I hope it offers people an ext of an appreciation of the life ~ above this planet," de Kok-Mercado said.

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This story was noted by OurAmazingPlanet, a sister site to yellowcomic.com. With Douglas key at dmain
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