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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
Scientists Discover 'Octlantis,' a Bustling Octopus City
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Sylke Rohrlach, Wikimedia Commons // CC BY-SA 4.0

Octopuses are insanely talented: They’ve been observed building forts, playing games, and even walking on dry land. But one area where the cephalopods come up short is in the social department. At least that’s what marine biologists used to believe. Now a newly discovered underwater community, dubbed Octlantis, is prompting scientists to call their characterization of octopuses as loners into question.

As Quartz reports, the so-called octopus city is located in Jervis Bay off Australia’s east coast. The patch of seafloor is populated by as many as 15 gloomy octopuses, a.k.a. common Sydney octopuses (octopus tetricus). Previous observations of the creatures led scientists to think they were strictly solitary, not counting their yearly mating rituals. But in Octlantis, octopuses communicate by changing colors, evict each other from dens, and live side by side. In addition to interacting with their neighbors, the gloomy octopuses have helped build the infrastructure of the city itself. On top of the rock formation they call home, they’ve stored mounds of clam and scallop shells and shaped them into shelters.

There is one other known gloomy octopus community similar to this one, and it may help scientists understand how and why they form. The original site, called Octopolis, was discovered in the same bay in 2009. Unlike Octlantis, Octopolis was centered around a manmade object that had sunk to the seabed and provided dens for up to 16 octopuses at a time. The researchers studying it had assumed it was a freak occurrence. But this new city, built around a natural habitat, shows that gloomy octopuses in the area may be evolving to be more social.

If that's the case, it's unclear why such octo-cities are so uncommon. "Relative to the more typical solitary life, the costs and benefits of living in aggregations and investing in interactions remain to be documented," the researchers who discovered the group wrote in a paper published in Marine and Freshwater Behavior and Physiology [PDF].

It’s also possible that for the first time in history humans have the resources to see octopus villages that perhaps have always been bustling beneath the sea surface.

[h/t Quartz]

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This Just In
Criminal Gangs Are Smuggling Illegal Rhino Horns as Jewelry
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Valuable jewelry isn't always made from precious metals or gems. Wildlife smugglers in Africa are increasingly evading the law by disguising illegally harvested rhinoceros horns as wearable baubles and trinkets, according to a new study conducted by wildlife trade monitoring network TRAFFIC.

As BBC News reports, TRAFFIC analyzed 456 wildlife seizure records—recorded between 2010 and June 2017—to trace illegal rhino horn trade routes and identify smuggling methods. In a report, the organization noted that criminals have disguised rhino horns in the past using all kinds of creative methods, including covering the parts with aluminum foil, coating them in wax, or smearing them with toothpaste or shampoo to mask the scent of decay. But as recent seizures in South Africa suggest, Chinese trafficking networks within the nation are now concealing the coveted product by shaping horns into beads, disks, bangles, necklaces, and other objects, like bowls and cups. The protrusions are also ground into powder and stored in bags along with horn bits and shavings.

"It's very worrying," Julian Rademeyer, a project leader with TRAFFIC, told BBC News. "Because if someone's walking through the airport wearing a necklace made of rhino horn, who is going to stop them? Police are looking for a piece of horn and whole horns."

Rhino horn is a hot commodity in Asia. The keratin parts have traditionally been ground up and used to make medicines for illnesses like rheumatism or cancer, although there's no scientific evidence that these treatments work. And in recent years, horn objects have become status symbols among wealthy men in countries like Vietnam.

"A large number of people prefer the powder, but there are those who use it for lucky charms,” Melville Saayman, a professor at South Africa's North-West University who studies the rhino horn trade, told ABC News. “So they would like a piece of the horn."

According to TRAFFIC, at least 1249 rhino horns—together weighing more than five tons—were seized globally between 2010 and June 2017. The majority of these rhino horn shipments originated in southern Africa, with the greatest demand coming from Vietnam and China. The product is mostly smuggled by air, but routes change and shift depending on border controls and law enforcement resources.

Conservationists warn that this booming illegal trade has led to a precipitous decline in Africa's rhinoceros population: At least 7100 of the nation's rhinos have been killed over the past decade, according to one estimate, and only around 25,000 remain today. Meanwhile, Save the Rhino International, a UK-based conservation charity, told BBC News that if current poaching trends continue, rhinos could go extinct in the wild within the next 10 years.

[h/t BBC News]

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