For animals out there in the wild, it's all about survival.
It's important to find food and not be food.
And for a lot of animals, they do this just like you were I would... with their eyes.
But not all eyes are the same.
Animals evolved at different times in different environments,
meaning there are whole lot of different eyes out there working in different ways
all in the name of survival.
As a veterinarian who has traveled the world working with different animals in different
places, I've seen this firsthand and it never ceases to amaze me.
One of my favorite eyes are goat eyes, which have these horizontal rectangular pupils,
great for seeing wider ranges helping to locate predators, when they're grazing.
Colossal squid have the biggest eyes in the world,
some think the biggest ever, they've evolved to see large
objects far away, perfect for spotting sperm whales looking for lunch.
But today we're going to be talking about owl eyes.
Now there are a lot of things that make owls fascinating animals and fierce hunters;
powerful beaks and talons, feathers that actually help them reduce noise as they flap, and some species
actually have asymmetrical ears.
One is higher than the other.
And that helps them locate prey better in the dark.
But today I really want to talk about their eyes, and not just because I have this skull,
but it helps.
This is my great horned owl skull, and it's one of my favorites because I mean if you
look at his eyeballs.
And you think about the mass, the actual volume that is occupied by eyeballs, it's maybe as
much or more than the brain or the rest of the skull, and they're big for a reason.
The bigger the eyes, the more the pupils can expand to let in light, which helps them
see in the dark.
That's why you see a lot of nocturnal animals with those big eyes like the tarsier.
We're not really going to get into the details of the tarsier but come on, we needed to
show you what they look like.
Bigger eyes also means more space between the lens,
the front of the eye, and the retina at the back of the eye.
This distance helps the owl's eyes focus on a bigger and more sharp image on their retina,
resulting in their impressive vision.
For example, the tawny owl can see about two or three times better than us humans, but
of course vision varies from owl to owl.
The other amazing thing about owl eyes is their shape.
Usually when referencing eyes we talked about eyeballs.
But in this case, owls have eye tubes.
Scientists believe that as birds evolved, their center of gravity moved to the center
of their body to help with the balance of flying.
So their heads had to become lighter.
This is the reason owls have tubular eyes, a tubular eye takes up less space than a round
or globular eye, and in turn weighs less, but it doesn't lose that distance between the
lens and the retina.
So the owl can have a lighter eye, and still maintain their amazing vision, but this tubular
shape also meant they lost some of their peripheral vision.
The opposite of those goat eyes I love so much.
Owl eyes are also fixed socket eyes, held in
place by a bone called the sclerotic ring. This along with their limited peripheral vision
means that if an owl wants to see left, right, up or down,
they have to physically move their head.
Luckily, they've evolved in a way to help them do that.
Now you may have heard the fact that owls can turn their heads 270 degrees, which might
be true, but this fun fact might be a little deceptive.
First off, if I told you I could rotate my head 180 degrees, would you believe me.
Well, let me show you.
See, this 270 degree fact isn't telling you the starting point, which makes it a little
misleading.
Now what owls can definitely do is see behind them, and even further if
they need and turn completely upside down.
This is all due to a few things.
First, most owls have 14 neck vertebrae.
Humans have just seven.
This gives them that amazing flexibility, but their flexibility is also thanks to the
joint between their neck and their head called the atlanto-occipital articulation joint.
Now as humans have two of these joints that are connected to our skull, giving us limited
range, but owls only have one, giving them the ability to pivot around, kind of like
a robot.
These two adaptations help make up for the fact that they can't move their eyes.
So taking in all this information about their eyes, their skulls, their necks, not to mention
the things we didn't get into like their ears, feathers, beaks, wings, talons, you can start
to get a picture of why these birds are such elite hunters, but that doesn't mean they're
immune to the troubles affecting so many animals out there.
Look at my little patient today.
This is a screech owl.
Pretty cool, huh?
From a conservation standpoint my experience when working with owls has mostly been with
wildlife rescues, and these are animals that were maybe orphaned or they were injured.
And so they need some medical help to potentially and hopefully get them back into the wild.
Luckily, around the world are amazing organizations studying owls rescuing owls and helping preserve
not only new generations, but the environments where they live.
Because look owls not only have an important place in the ecosystem.
They can also greatly benefit us.
Farmers harness the power of owls' amazing eyes to help naturally
control rodent populations that could harm crops.
And on top of all that, they're amazing to see in the wild.
So let's all work together to make sure they're here for a long time.
Thank you so much for watching our new Seeker series Tusks to Tails.
I'm Dr. Evan Antin and and if there's an animal you'd like us to feature, leave it in the
comments.
We'll see you next time.