Are Bats Really Blind? Discover the Truth about Bat Vision
When someone refuses to accept the obvious, you may say that they’re as blind as a bat. Bats tend to fly erratically when hunting at night and rely heavily on echolocation to pursue prey, which leads people to assume that bats are blind.
So, are bats really blind?
Here is a closer look at how bats see and where the idea that bats are blind comes from.
What Does Blind as a Bat Mean?
The words “as blind as a bat” are an example of a simile. A simile is a figure of speech comparing two separate, unrelated things. You may describe someone as being “as blind as a bat,” “as crazy as a fox,” or “as brave as a lion”.
Not all lions are brave and foxes are not crazy. These expressions are used to make a statement more impactful.
Where Does the Expression “Blind as a Bat” Come From?
The origin of “blind as a bat” is not entirely known. However, Greek philosopher Aristotle once said, “For as the eyes of bats are to the blaze of the day, so is the reason in our soul to the things which are by nature most evident of all.”
Aristotle’s quote references the belief that bats cannot see well during the day. Over two thousand years later, many people still believe that bats are virtually blind.
Bats Use Echolocation to Hunt and Track Prey
Scientists have identified over 1,400 species of bats. You can find bats in almost every part of the world, other than the polar regions and hot deserts.
The smallest bat species, the Bumblebee Bat, weighs just two grams and has a wingspan of about six inches. The Giant Golden-Crowned Flying Fox weighs several pounds and can have a wingspan of up to six feet.
While bats come in a variety of sizes, almost all species use echolocation to navigate at night. The fruit bats that belong to the family Pteropodidae, which includes the flying fox, are the only bats that do not use built-in sonar.
Echolocation helps bats fly in pitch-black environments. Bats often live in caves, trees, mines, and other structures that provide darkness.
Using echolocation involves emitting high-pitched sounds at frequencies above what the human ear can hear. The range of frequencies emitted by bats falls into the “ultrasound” frequency range.
The ultrasound frequencies bounce off nearby objects. After bouncing off objects, the sound waves travel back to the bat. Bats can recognize the frequencies of their calls, allowing them to detect the presence of animals and structures.
Different species of bats rely on echolocation more than other species. For example, the common vampire bat relies heavily on echolocation and often only feeds during the darkest hours of the night. Many species of fruit bats have sonar but use echolocation sparingly or not at all.
Do Bats Have Poor Eyesight?
Most species of bats have poor eyesight compared to humans when they are traveling during the daytime, but they can see much better than we do in the dark.
Bats have small eyes and sensitive vision. Scientists have determined that the eyes of bats are adapted to both daylight and UV light. As with many nocturnal mammals, bats can see better at night than during the day, but they are not blind.
The retina of the eye has two types of cells that sense light. These cells are called cones and rods. Cones allow you to sense color but require bright light, such as sunlight. Rods allow you to sense dark, scattered light.
Bats and other nocturnal mammals have a higher ratio of rods to cones. For example, the retina of the human eye contains four rods for everyone one cone cell. Only about 2% to 4% of the bat’s light-sensing cells are cones.
Bats can see in the day and night but cannot make out the full range of colors that we perceive. However, they can detect the location of objects in the dark better than humans, even without echolocation.
Why Do Bats Fly Erratically at Night?
Bats often fly erratically when searching for food, especially when hunting for insects. The erratic flight path is one of the reasons people believe that bats have poor eyesight.
The seemingly erratic behavior of bats is due to their ability to mimic the movement of insects. Insects are the primary food source for many species of bats.
Bats have exceptional control over their bodies and wings. The wings of a bat contain over two dozen joints, compared to the few joints found in the wings of birds and insects.
Unlike birds, insects can quickly change directions midflight and may appear to fly erratically instead of in swooping motions. Bats mirror the movement of insects as they track their prey.
Conclusion
The idea that bats are blind is a myth. Bats can see better than humans at night and can still see during the day. While bats can see, they often use echolocation and their sensitive hearing to help navigate caves and other dark environments.
In the end, you should always double-check the facts before believing what you read or hear about bats — or anything else for that matter.
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