Are sharks blind? The black “lifeless” eyes of the shark strike dread into the hearts of many. They have also led us to believe that sharks are blind. This isn’t true, although some shark species are visually impaired, and others are completely color blind.
In general, sharks have highly sophisticated eyes that are similar to a human’s in both “structural and functional complexity.” They also have their drawbacks, however, which is partly why the notion that sharks are blind has persisted for so long.
We’re often told that sharks don’t mean to attack humans and that it’s purely a case of mistaken identity. If that’s true, it suggests that sharks have comparatively poor eyesight as they can’t differentiate between a human and a seal.
Despite that, recent studies suggest that not only can sharks see, but their vision is considerably better than previously thought, although it does vary dramatically from species to species.
As executive director of the Ocean First Institute, Mikki McComb-Kobza, says, “The story of shark eyes is a story of tremendous diversity.”
How Does a Shark’s Eyesight Work?
Humans and other terrestrial predators have binocular vision. In other words, both eyes face the same direction. This positioning gives us a superior depth perspective and enables us to see in three dimensions, both of which are critical when hunting high-speed prey on land.
Although the shark is an apex predator, its eyes are on either side of its head, giving it much greater peripheral vision. Unfortunately, it also means he has two blindspots – one right in front of his nose and another behind his head.
As a result, sharks have poor depth perception and object detection. However, when it comes to night vision, the shark outdoes the human 10:1.
Reading Suggestion: Do Sharks Jump Out of the Water?
Sharks’ eyes have adapted to maximize the amount of light available. Behind the retina lies a layer of mirrored crystals called the tapetum lucidum. This feature increases visual sensitivity by reflecting the light back into the light-sensitive cells of the retina, giving them a “second opportunity for photon-photoreceptor stimulation.”
In other ways, however, the structure of the shark’s eye is almost identical to that of a human’s. The anatomy of our eyes is so similar that “shark cornea has been used in human eye surgery.”
10 Questions About What Sharks Can See
#1 Are Sharks Blind?
Sharks aren’t blind and have much better eyesight than previously believed. While they struggle to distinguish colors and detect objects, a shark’s vision is still sufficient enough for it to perform death-defying feats when pursuing its prey.
The mysterious Greenland shark is probably the most visually impaired, but not because of genetics.
Although they are an apex predator, Greenland sharks are widely believed to be sluggish and slow-moving. This could explain why they seem to be able to co-exist with the parasitic copepods that “cause eye damage, resulting in vision impairment, including partial blindness.”
Scientists studying the copepods and their shark hosts concluded that “these infections do not significantly debilitate hosts because they probably do not need to rely on acute vision for their survival.”
Reading Suggestion: How Close To The Shore Do Sharks Come?
This is hard to believe, given that Greenland sharks have reportedly leaped out of the water to grab caribou that strayed too close to the edge. Either way, with Greenland sharks reaching over 200 years of age, the parasitic copepod doesn’t seem to impact their ability to survive.
In the past, scientists had concluded that “due to the small size of whale shark eyes compared to the rest of their body,” this shark species had poor vision and relied very little on this sense. In 2020, however, a study revealed that the nictitating membrane of the whale shark’s eye is covered with “modified teeth-like structures,” known as dermal denticles.
“These highly protective features of the whale shark eye seem to contradict those previous theories, emphasizing the importance of vision for environmental perception.”
Reading Suggestion: How Do Sharks Die?
#2 Are Sharks Blind and Deaf?
Although sharks don’t have any visible ears, they are no more deaf than they are blind. Sharks have an acute sense of directional hearing that enables them to detect low vibration frequencies and locate potential prey.
The only external indications of a shark’s ears are two small holes situated just behind the eyes. On the inside, a chain of fluid-filled sacs and ducts make up the shark’s ear and respond to vibrations in the water.
When a sick or old fish “emits an irregular wave pulsed sound of a very low frequency between 20 to 300 Hertz,” the shark “hears” this and subsequently responds.
According to a study by otolaryngologist Jeffrey Corwin, one part of the inner ear, known as the macula neglecta, “responds particularly strongly to vibrations through the top of the skull.”
This feature gives predatory shark species “an enhanced ability to hear sounds originating from above and in front.” In other words, they have accurate, directional hearing, which helps them locate their prey.
Reading Suggestion: Do Sharks Have Bones?
#3 Are Sharks Color-Blind?
Most sharks are color blind or have problems with object detection. Many species also “have poor spatial resolving power,” although this is much better in the pelagic and benthopelagic species sharks that feed on fast-moving prey.
As a sensory biologist, Dr. Craig O’Connell points out, “One of the most misunderstood aspects of a great white shark is its eyes.”
After dissecting a great white’s eyeball, however, Dr. O’Connell realized “They actually have pretty good vision.”
“The anatomy of the eye allows them to see light, movement, color, contrast, and detail,” he added.
Reading Suggestion: Can s Shark Drown?
Like us humans, sharks also have a spherical lens within the eye that adapts to focus on objects at varying distances. They don’t see color in the same way we do, however.
A recent study of the retinas of 17 different shark species off the coast of Australia indicates that most shark species “cannot tell different colors apart.”
Within the retina, there are two main types of light-sensitive cells. Rod cells respond to different levels of brightness while cone cells distinguish colors. 10 of the 17 species had no cone cells, while the remaining 7 had just one.
As there are over 400 species of shark, this isn’t enough to conclude that all sharks are color-blind. However, it does suggest that sharks rely more on contrast against the background than on color for object detection.
#4 What Colors do Sharks See?
Sharks don’t see colors per se, but they can distinguish between light colors and dark ones. A brightly colored swimming suit in yellow or orange is easier for us to see than a brown or dark blue one, and the same is true for a shark.
Anything that reflects the light close to the ocean’s surface also attracts the shark, as it looks so similar to its prey species.
#5 Are Sharks Attracted to Certain Colors?
Divers became so convinced that sharks love the color yellow above all others that they started calling it “yum, yum, yellow.”
Research has since proved that sharks don’t necessarily prefer yellow but are “attracted to any high-contrast color, such as yellow, orange, or red.”
In murky water, it’s much easier for a shark to detect an object that is brightly colored than one that blends in with a grey-blue background.
Reading Suggestion: Are Sharks Vertebrates or Invertebrates?
#6 How Does a Shark Detect Motion?
A shark isn’t only dependent on its vision for detecting motion and identifying potential prey. Its other senses include smell, taste, hearing, and touch. Researchers believe sharks use their acute sense of directional hearing to track down their prey but depend on two other specialized receptors to detect motion.
The first of those receptors is the lateral line system which can detect “low-frequency pressure changes” such as those caused by something moving through the water. Combined with the sharks’ ears, this creates an “acoustico-lateralis system” for motion detection.
The shark also has electroreceptor sensory cells that “connect with the outside seawater through gel-filled canals which open at pores on the skin.” Situated around the head, snout, and jaws, these cells help the shark locate its prey at the moment of attack when the blind spot in front of its nose makes its target invisible.
The shark also uses electroreception to identify the location of potential mates and navigate using the earth’s magnetic field.
#7 Are Sharks Blind when They Attack?
A shark is basically blind during the last moments of an attack. Sharks have two different methods of protecting their eyes when feeding, both of which render them virtually blind and heavily dependent on their other senses.
Although the great white and whale shark have eyelids, they don’t use them to protect their eyes. Instead, they roll them back in their heads using a movement known as an ocular rotation. This exposes a tough piece of cartilage that acts as a shield for the eye, protecting it against abrasion while feeding.
Other species use the third eyelid, called the nictitating membrane, to protect the eye. By extending this membrane from the lower corner of the eye, the shark covers the exposed parts, protecting the eye from damage and abrasion.
This last-minute blindness, in conjunction with the blind spots it already battles with, helps to explain why the shark sometimes struggles to differentiate between human and seal.
Reading Suggestion: Do Sharks Have a Tongue?
Think about it this way: you’ve got a fast-moving shark traveling at 10 meters per second, but he can’t see anything further than about 15 meters ahead of him. In other words, a shark can only see its prey for about 1.5 seconds before hs strikes, at which point his eye protection kicks in, rendering him virtually blind. No wonder it gets surfers and seals mixed up!
#8 What Sharks are Blind?
There are no completely blind species of shark. Even the blind shark (Brachaelurus waddi) can see perfectly well it just has a habit of retracting its eyeballs and closing its eyes when out of water.
The Greenland shark has extremely poor vision due to the parasites that infect its eyes, but even it isn’t completely blind.
The great white’s eyesight isn’t that good, especially in juveniles with less spatial resolving power than their adult counterparts. Researchers suspect this is because the adults have “larger eyes and a correspondingly longer focal length.”
#9 Do Sharks have Eyelids?
All shark species have at least two eyelids, and some have a third in the form of a nictitating membrane. The upper and lower eyelids aren’t mobile like ours, but the nictitating membrane is “a highly mobile structure,” capable of providing “rapid and efficient protection against abrasion.”
#10 What is the Best Color to Avoid Shark Attacks?
As sharks see contrasts rather than colors, your best chance of avoiding a shark attack is by blending in with your surroundings.
So leave your yellow swimsuit at home and pick out something that won’t contrast too much with the environment you’re in. Blue, black, or similarly dark colors are the best, although avoiding contrasting patterns will also help.
Reading Suggestion: The Incredible Life Cycle of a Shark
Despite common misconceptions, sharks aren’t blind. They have highly complex eyes that can change focus and reflect light to improve night-time visibility.
However, research suggests that sharks are predominantly color-blind and struggle with object detection at certain distances. They also have some significant blind spots and are almost completely blind when they attack their prey.
Researchers suspect that when shark attacks occur, it’s due to the shark’s inability to distinguish the human from a seal.
Reading Suggestion: How Long Can a Shark Survive Out of The Water?