scientists have solved the mystery of how owls can swivel their heads without suffering serious injury.
It is the result of uniquely evolved features of their bone structure and blood vessels.
The night-hunting owl can rotate its head as much as 270 degrees as it surveys the ground for prey. If other animals tried to do the same, fragile arteries in the neck would stretch and tear.
Humans commonly suffer such injuries as a result of whiplash in car and other accidents.
“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,” said Dr Philippe Gailloud, one of the researchers from Johns Hopkins University School of Medicine in Baltimore, US.
The team looked at the bone structure and network of blood vessels in the heads and necks of snowy, barred and great horned owls that had died from natural causes.
The researchers, whose work is reported in the journal Science, discovered several unusual structural features that appear to be unique to owls. They included wide tunnels in the neck bones through which arteries ran to the brain.
The cavities were around ten times wider than the vessels passing through them, creating air pockets that allowed the arteries to move around when twisted.
Blood vessels at the base of the head also appeared to balloon as they branched out – the opposite of what occurs in humans and other animals. As owls rotated their heads, this meant they could pool blood to meet the energy needs of their large brains and eyes.
The scientists also uncovered small connections between the carotid and vertebral arteries that permitted blood to flow between the two.
Exchanging blood between the arteries ensured uninterrupted flow to the brain, even if one route was blocked during extreme neck rotation.