Kobus Cilliers | On 29, Feb 2020

Darrell Mann

It is one way of seeing the world from a different point of view. This short-eared owl made sure to turn heads, by swivelling its face completely upside down. The bird was captured by wildlife photographer Alain Balthazard in Champagne-Ardenne, Northeastern France, but the same species can also be seen in Northern England and Scotland.

Owls are largely nocturnal and live lifestyles in which high visual acuity is important. In order to maximise visual sensitivity without losing resolution, owls have evolved large eyes that are tubular in shape. They are also forward-facing in order to retain reasonable binocular vision. However, a consequence of the eye being both large and tightly fitted within the orbit is a substantial loss of eye movement, and, being forward facing they have a narrow field of view.

Owls compensate for these constraints on eye movement and visual field by having an extremely well-developed capacity to move their heads, linked to long and flexible necks. As a result, they can turn their heads through up to 270 degrees, whereas a hawk or falcon could manage no more than about 180 degrees.

The new problem that emerges from the need to re-orient the head by such a large amount is enduring continuity of blood supply to the brain. As various different muscles stretch and twist to move the head, arteries become squashed and so aren’t able to flow enough blood.

This makes for a classic angle (of moving object) versus loss of substance contradiction. About which the Contradiction Matrix has this to say:

So how do owls solve the conflict? Well, first, they have (Principle 1, Segmentation) double the number of bones in their necks compared with humans, fourteen instead of seven. Next, they (Principle 15, Dynamics) manage oxygen in the blood to allow a steady supply even when the twisting effect is restricting blood flow. Thirdly, (Principle 4, Asymmetry) the arteries are positioned in a centralized position (as opposed to being homogenously distributed throughout the neck) so as to minimize their distortion as the neck twists. And then, fourthly, (Principle 10, Prior Action) they are able to ‘pool’ blood in a kind of plenum chamber, just in case a twisting motion does impede the blood flow too much.

Simple when you know how. Especially when written up by our friends at Sketchplanation: