Sharks are able to see in low light, murky, and dark water, although the specific degree of which depends on the species and the habitat they occupy.
Sharks are known to predate at night when much of their prey rises to the surface, so it’ll seem kind of strange if they couldn’t see in the dark, right? Strangely enough though, the anatomy of the shark’s eye is quite similar to ours despite them being capable of seeing up to ten times better than us in clear water!
Don’t worry; we’ll solve this mystery in this article as I explain why this is the case and what their overall vision is like.
How Do Sharks’ Eyes Work?
Sharks’ eyes work through a combination of the cornea, iris, lens, retina, and pupil, along with the two photoreceptors, the rods and cones (pic 1).
The cornea acts as a protective barrier against dust and other particulates. The pupil and iris control the amount of light let into the eye. The lens help refract the light to focus on the retina, which processes the light and sends the signals to the brain via the optic nerve.
The rods and cones are part of the retina; hence they help process light, with the rods helping sharks see in low-light levels, and the cones at higher-light and help sharks see color.
If you look at the above diagram, you might notice an object called the tapetum lucidum located just behind the retina. This is the crucial part of the eye that allows sharks to see in the dark, as it consists of numerous mirrored crystals that reflect light back to the retina.
This means that the retina is given another chance at detecting the light once it’s reflected off the tapetum lucidum.
Another difference between a shark’s eye and a human’s eye is the lack of additional cones.
Although it is still difficult to understand how sharks perceive color, it is known that sharks only have one cone. Hence, they are quite limited to the amount of color they can see.
A third difference is the presence of a protective membrane called the nictitating membrane.
Only some sharks have the nictitating membrane that’s used for additional protection when it comes to feeding or interacting with other sharks. Those who lack it will instead roll their eyes into the back of their head to compensate.
Although sharks can have different eye shapes and sizes depending on factors such as their habitat (whether they live closer to the surface or in the deep ocean) and overall size (eye growth is positively correlated with body length), they function in pretty much the same way.
What is a Shark’s Vision Like?
When you think about a shark, you probably think of them as having a pointed snout with eyes on either side. This is certainly almost always the case (nope, there’s no catch), and it’s because of this that sharks have close to a 360-degree field of vision!
However, because of the unique location of their eyes, many sharks have two blind spots, one directly in front of their snout and one behind their head.
Now, these blind spots perhaps don’t sound too detrimental, but sharks have nonetheless found a way to navigate around these setbacks, mainly by waving their heads from side to side.
They may also circle an object to be able to keep it in view (as you might’ve seen great whites do).
Although sharks can see much better than us in the dark and muddy waters of the deep ocean, the majority can only see about 50 feet (15 meters) ahead in normal conditions.
Hence, most sharks will only take advantage of their vision once they have closed in on their prey.
Can Sharks See at Night?
Although some sharks, such as juvenile great white sharks, might prefer diving into deeper waters during a full moon to take advantage of the greater light intensity and find prey, the majority are very much capable of seeing at night, even at great depths.
In fact, most sharks prey either at night or during the early or late hours of the day.
Hopefully, this article was just as interesting for you as it was for me, considering how similar sharks’ eyes are to our own.
In fact, something I didn’t mention earlier was that the tapetum lucidum is also present in cats’ eyes, which is actually why they seem to glow.
So, the next time you see a pair of shining eyes coming at you in the dark, be wary (especially if it’s underwater)!