Owls are famous for the incredible way they can turn their heads around without moving their lower bodies at all, an adaptation allowing them to zero in on visual targets without alerting potential prey, or predators, with their body movements. While popular mythology has it that owls can turn their heads all the way around, in actuality they only had a 270 degree range of motion, but that’s still pretty darn impressive.
This rather unique physical talent allows owls to get the jump on dinner, and it’s also long been a fascination for researchers. In most animals, including humans, a neck rotation that extreme would be deadly, because it would put such pressure on the blood vessels in the neck that they’d cut off the blood supply to the brain. Researcher Philippe Gailloud got curious about how owls managed to stay alive: “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.”
Using the facilities at Johns Hopkins and the bodies of barred, great horned, and snowy owls who had died of natural causes, he took a closer look at their unique anatomy, performing a number of medical imaging studies as well as dissecting the birds. What he learned was fascinating: several key anatomical adaptations facilitate smooth head movement for these nocturnal birds. For one thing, the vertebral artery enters the neck at a higher point, creating some slack in the vessel that allows it to move with the bird’s head, and microconnections between the vertebral and carotid arteries allow for exchange of blood between the two points. If one vessel is blocked, the other can still supply the head.
Furthermore, the blood vessels enlarge as they enter the head, which is highly unusual. Typically, the further away from the heart, the smaller a vessel, as this maintains the pressure of the vascular system and ensures an even supply of blood throughout the body. In owls, the enlargement creates pockets that can fill with blood, allowing the bird to effectively store blood supplies, which comes in handy when normal pathways to the head are blocked. Furthermore, the holes in the vertebrae through which the blood vessels thread are much larger, which creates much more of a range of motion.
Humans aren’t so lucky. The supply of blood to the head and neck is fragile, and very susceptible to extreme rotation and violent head movements. Owls enjoy a number of protections to keep their blood vessels intact, while humans have to be careful about moving their heads and necks: one reason why emergency medical teams are so careful in situations where people have suspected head and neck injuries, as the wrong movement could cause serious damage or death.
This research shows that you never know where science will strike next, and that there’s always something more to learn about life on Earth.
For that matter, you never know who might make an unlikely friend:
Photo credit: Brisbane Falling