By Jonathan Amos
Science correspondent, BBC News
It's the owl's greatest trick - turning its head
almost a full circle.
The puzzle has been how the bird doesn't
throttle itself in the process. If we did it, we'd cut the blood supply to our
brains and pass out.
But according to two US-based scientists, the
owl has some very smart bone and vascular structures running along its neck to
the skull.
These features protect blood vessels from damage
and maintain the flow even when the head is swivelled 270 degrees.
"They haven't developed just one answer to
the problem; they have several answers," said Dr Philippe Gailloud from
Johns Hopkins University School of Medicine.
"And it's because of this set of solutions
that we don't see lots of owls lying on the forest floor having suffered
strokes," the interventional neuroradiologist told BBC News.
Most birds have extremely flexible necks, but
the owls are the avian species that have perhaps garnered the greatest
attention for their neck-twisting exploits.
They must turn their heads in this extraordinary
way because of their eyes' narrow field of view and relative immobility.
It's true they have double the number of bones
in their neck compared with us - 14 versus seven cervical vertebrae. But it's
really the way the animal manages the flow of oxygenated blood to its brain
that underpins the impressive feat.
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