owls

WTF Fun Fact 13584 – Owls Don’t Have Eyeballs

Owls don’t have eyeballs. At least not in the traditional sense.

If Owls Don’t Have Eyeballs, What Do They Have?

Owls possess elongated, tubular eyes that are fixed in their sockets. This unique design provides them with exceptional vision, especially in low light.

The reason behind this peculiar eye shape is all about maximizing light intake and enhancing their depth perception. With their long, tube-shaped eyes, owls can collect and process a significant amount of light. This feature is vital for a creature that does most of its hunting during twilight hours or in the dark of the night.

Now, since owls can’t move their eyes within their sockets like humans can, they’ve developed an incredible neck flexibility. An owl can rotate its head up to 270 degrees in either direction. Imagine turning your head almost entirely backward! This ability allows them to have a wide field of view without needing to move their bodies.

The Trade-Off

There’s always a trade-off in nature. While owls can see far and wide with their tubular eyes, their peripheral vision is limited. That’s where their keen sense of hearing comes into play. Together with their exceptional eyesight, their auditory skills make them formidable nocturnal hunters.

An owl’s retina has an abundance of rod cells, which are sensitive to light and movement. These cells help the owl detect even the slightest movement of prey in dimly lit conditions. And while they have fewer cone cells, responsible for color vision, recent studies suggest that owls can see some colors, particularly blue.

Given the size and prominence of an owl’s eyes, protecting them is crucial. Owls have a third eyelid known as a nictitating membrane. This translucent lid sweeps across the eye horizontally, acting as a windshield wiper to remove dust and debris. It also helps in keeping their eyes moist.

The unique eye structure of owls has fascinated scientists and researchers for years. By studying how owls see, we gain insights into improving visual technologies, especially those required to function in low-light conditions.

— WTF fun facts

Source: “Do Owls Have Eyeballs: The Unique Vision And Skills Of Owls” — DiscoveryNatures

WTF Fun Fact 12746 – Owls Don’t Have Eyeballs

Owls have eyes, of course. But owls don’t have eyeballs.

Instead, owls have eyes shaped like cylinders (with three eyelids!). Because of this shape, owls can’t roll their eyes around while keeping their heads still. That’s why they have to move their heads around too much to look around.

How do owls see without eyeballs?

According to the Office of Science & Society at McGill University: “Since moving their torsos would likely make noise that would alert their prey to their presence, owls have evolved to have necks that can spin up to 270° essentially silently.”

But why would an owl evolve to have eye rods instead of eyeballs? Wouldn’t it just be easier not to have to move your head at all in order to see to the side?

Well, perhaps, but the benefit of having eyes shaped like rods instead of balls is that not only does it allow them to see better in the dark but it’s the optimal shape for an animal with such a small skull.

The benefit of eye rods

As you may have noticed, nocturnal animals tend to have large corneas. That’s so any light can be collected more efficiently, allowing them to see in the dark.

As it turns out, these elongated eye tubes make it even easier for them to see the way they need to, even if they do have to make more movement in order to get a larger field of vision (also called binocular vision). Without moving their heads, their visual field is about 110 degrees (a human’s is 180 degrees, for comparison).

Binocular vision

Binocular vision also lets owls see objects in three dimensions (height, width, and depth). So, it turns out an owl’s eyes are pretty perfectly suited to its lifestyle.

While some believe all of this means that owls can’t see during the day because they’re blinded by too much light, that’s simply not true. Some owls can see even better than humans in the daylight as well, despite the lack of eyeballs.

At least you never have to worry about an owl giving you the side-eye. – WTF fun facts

Source: “Owls Don’t Have Eyeballs” — Office of Science & Society, McGill University