How Far Can Turtles See?
When we think about what makes our eyes special, it’s usually something along these lines: We are able to see colors, perceive depth, recognize faces…
But there are other things that make us unique as well.
For example, some people have amazing night-vision abilities (like bats or mantis shrimp).
Other animals have remarkable hearing – like dolphins and whales.
And then there are those who can smell their prey miles away without lifting a head.
What animal has all three features?
That would be a Turtle!
But not just any kind of Turtle, a Tortoise.
With their ability to bury themselves into the ground for months at a time, they’re considered cold blooded reptiles.
So, does this mean they don’t get hot under the collar when danger comes knocking on their door?
They might take cover but they will definitely do everything possible to avoid being eaten by predators.
So, what exactly sets them apart from most other reptiles?
Well first off, let’s talk about the basic anatomy that gives them an advantage over many other species.
Like humans, turtles also possess two different types of eyes.
The left one is called the “Pterotic Eye” and the right one is the “Opticula”.
These both function independently of each other allowing for 360 degree panoramic vision.
This means that if a predator gets too close, the turtle can look behind him/herself instantly.
It’s important to note that while human eyes rely mainly on rods and cones for color perception, tortoises use rods only for black and white images.
However, because they have no pigment cells in the retina, they cannot distinguish between shades of gray.
Since turtles spend so much time buried underground during the day, a lot of their visual information comes through vibrations.
When light hits the earth, small particles bounce back towards the surface which allows them to see even better in low lights than other creatures with pigmented retinas.
In addition, turtles’ pupils dilate up to 20 times wider than ours making them more sensitive to changes in lighting conditions.
Also, unlike snakes, turtles have eyelids that blink regularly instead of constricting around the pupil.
Finally, when frightened, turtles release carbon dioxide through their nostrils rather than perspiring the way lizards do.
Now that we’ve discussed the basics, lets discuss the actual distance that turtles are capable of seeing.
The Distance a Turtle Can See
First of all, it should come as no surprise that turtles have poor eyesight compared to humans.
As previously stated, due to their lack of pigment cells in the retina, tortoises are unable to discern colors.
On top of that, since turtles live mostly underground where the sun doesn’t shine for long periods of time, they need to develop ways to survive in complete darkness.
Luckily, turtles have another trick up their sleeve.
Just like fish, turtles produce melatonin.
Melatonin helps regulate sleep cycles and therefore regulates metabolism. Its main purpose is to help organisms cope with stress such as extreme temperatures.
Because its production increases dramatically in response to sunlight, turtles must stay out of direct sunlight whenever possible.
Hence why they often camouflage themselves using dirt and leaves.
Another thing to keep in mind is that turtles don’t have stereoscopic vision.
Meaning, they aren’t aware of distances based upon perspective.
Instead, they navigate the world solely by sound and vibration.
Although, it may seem counter-intuitive, turtles generally prefer to move toward sounds rather than smells.
One reason could be that turtles are very slow moving and thus vulnerable to attack.
Another possibility is that turtles are attracted to the noise caused by digging.
By following their natural instincts, they are able to find food sources and escape dangers.
Next, lets address whether turtles can actually see from far away.
Yes, turtles are able to see quite clearly, especially in bright light.
However, contrary to popular belief, turtles do have a blind spot directly above their mouths.
The blind area measures approximately 3 inches wide and 2 inches tall and covers the part of the brain responsible for processing incoming sensory data.
If you were to cut across the middle of this region, you’d notice a thin line running horizontally through it.
The fact that Turtles have this hole shows that they have limited peripheral vision.
Peripheral vision refers to objects seen outside the central field of view.
Basically, this means that your peripheral vision extends beyond 180 degrees of straight ahead.
Humans have about 220 degrees.
Interestingly enough, turtles are believed to have great peripheral vision thanks to their large eyeballs.
Finally, lets get down to brass tacks and answer the question:
Do turtles see well in the dark?
No, turtles are completely blind below the level of their heads when looking upwards.
Below this point lies a portion known as the ‘tortois midbrain’.
At birth, this section contains nerve fibres that connect the optic nerves coming from both sides of the brain together.
Afterward, these fibers turn into bundles and connect the upper side of the midbrain to the lower half.
When this happens, tortoises lose almost all sense of direction.
Nowadays scientists believe that this serves little purpose considering turtles spend most of their lives buried underground.