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How Can Owls Rotate Their Heads 270 Degrees Without Dying?

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For humans, sudden gyrations of the head and neck—whether they’re from car accidents, rollercoaster rides, or chiropracty gone awry—can tear blood vessel linings in the neck, leading to clots that can cause stroke. Not so in owls, which can quickly rotate their heads 270 degrees in either direction without damaging blood vessels or cutting off blood flow to the brain. How do they do it?

To solve the mystery, scientists at Johns Hopkins—led by medical illustrator Fabian de Kok-Mercado and neuroradiologist Philippe Gailloud—used angiography and CT scans to examine the anatomy of a dozen snowy, barred, and great horned owls that died from natural causes. They discovered that the birds are equipped with four biological adaptations that prevent injury from rapid rotational movement; their study appears in the latest issue of Science.

“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," Gailloud said in a press release announcing the results of the study. "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.”

After x-raying, dissecting and analyzing blood vessels from the dead birds’ necks, the researchers injected dye into the dead owls’ arteries to mimic blood flow and manually turned their heads. What they found was surprising: Unlike in humans, whose arteries shrink as the head turns, the blood vessels just under the jaw at the base of the owls’ heads got increasingly larger as more of the dye entered, but before the fluid pooled into reservoirs. These contractile reservoirs, scientists say, are what allow owls to turn their heads so radically while still having enough blood to feed the eyes and the brain. What's more, a complex supporting vasular network minimizes interruptions in blood flow; the scientists discovered that owls have small vessel connections between the carotid and vertebral arteries that allow blood to flow between the two vessels—so even if one route is blocked by an extreme neck rotation, another can provide an uninterrupted blood flow to the brain.



Click to enlarge.

Bones in owls’ necks also have adaptations designed to facilitate extreme rotation. One of the major arteries feeding the birds' brains passes through holes in the vertebrae, called transverse foramine; the team found that these holes were 10 times larger in diameter than the artery. This extra space creates air pockets that allow the artery to move around when twisted; 12 of the vertebrae in the owls’ necks had this adaptation. "In humans, the vertebral artery really hugs the hollow cavities in the neck. But this is not the case in owls, whose structures are specially adapted to allow for greater arterial flexibility and movement," said de Kok-Mercado. Plus, the owls’ vertebral artery enters the neck higher than it does in other birds’—going in at the 12th cervical vertebrae, rather than the 14th—allowing for more slack.

"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," 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 team created a poster (above) that details their findings, and next plans to study hawk anatomy to see if those birds have similar adaptations for head rotation.

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Animals
Owning a Dog May Add Years to Your Life, Study Shows
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We've said that having a furry friend can reduce depression, promote better sleep, and encourage more exercise. Now, research has indicated that caring for a canine might actually extend your lifespan.

Previous studies have shown that dog owners have an innate sense of comfort and increased well-being. A new paper published in Scientific Reports and conducted by Uppsala University in Sweden looked at the health records of 3.4 million of the country's residents. These records typically include personal data like marital status and whether the individual owns a pet. Researchers got additional insight from a national dog registry providing ownership information. According to the study, those with a dog for a housemate were less likely to die from cardiovascular disease or any other cause during the study's 12-year duration.

The study included adults 40 to 80 years old, with a mean age of 57. Researchers found that dogs were a positive predictor in health, particularly among singles. Those who had one were 33 percent less likely to die early than those who did not. Authors didn't conclude the exact reason behind the correlation: It could be active people are more likely to own dogs, that dogs promoted more activity, or that psychological factors like lowered incidences of depression might bolster overall well-being. Either way, having a pooch in your life could mean living a longer one.

[h/t Bloomberg]

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Big Questions
Why Don't We Eat Turkey Tails?
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Turkey sandwiches. Turkey soup. Roasted turkey. This year, Americans will consume roughly 245 million birds, with 46 million being prepared and presented on Thanksgiving. What we don’t eat will be repurposed into leftovers.

But there’s one part of the turkey that virtually no family will have on their table: the tail.

Despite our country’s obsession with fattening, dissecting, and searing turkeys, we almost inevitably pass up the fat-infused rear portion. According to Michael Carolan, professor of sociology and associate dean for research at the College for Liberal Arts at Colorado State University, that may have something to do with how Americans have traditionally perceived turkeys. Consumption was rare prior to World War II. When the birds were readily available, there was no demand for the tail because it had never been offered in the first place.

"Tails did and do not fit into what has become our culinary fascination with white meat," Carolan tells Mental Floss. "But also from a marketing [and] processor standpoint, if the consumer was just going to throw the tail away, or will not miss it if it was omitted, [suppliers] saw an opportunity to make additional money."

Indeed, the fact that Americans didn't have a taste for tail didn't prevent the poultry industry from moving on. Tails were being routed to Pacific Island consumers in the 1950s. Rich in protein and fat—a turkey tail is really a gland that produces oil used for grooming—suppliers were able to make use of the unwanted portion. And once consumers were exposed to it, they couldn't get enough.

“By 2007,” according to Carolan, “the average Samoan was consuming more than 44 pounds of turkey tails every year.” Perhaps not coincidentally, Samoans also have alarmingly high obesity rates of 75 percent. In an effort to stave off contributing factors, importing tails to the Islands was banned from 2007 until 2013, when it was argued that doing so violated World Trade Organization rules.

With tradition going hand-in-hand with commerce, poultry suppliers don’t really have a reason to try and change domestic consumer appetites for the tails. In preparing his research into the missing treat, Carolan says he had to search high and low before finally finding a source of tails at a Whole Foods that was about to discard them. "[You] can't expect the food to be accepted if people can't even find the piece!"

Unless the meat industry mounts a major campaign to shift American tastes, Thanksgiving will once again be filled with turkeys missing one of their juicier body parts.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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