Tag: bats

Human Echolocation – Seeing With Your Ears

By Anupum Pant

Bats can see, but Daniel Kish can’t. Due to Retinal Cancer (Retinoblastoma), Daniel has been completely blind since the age of 13 months. To save his life, both his eyes had to be removed at a young age. But, even with no eyes, he can see. He sees with his ears. People call him the real-life batman.

What? When Daniel was young, he started making a clicking sound with his tongue to understand his environment. Little did he know, at a young age, he had mastered Echolocation – A technique used by dolphins, and bats to navigate when there is no light. At the age of 11, only when a friend told him about Echolocation, did he realize what he was really doing.

How? By listening to the reflected clicking sound, Daniel is able to map the shape, dimension, depth and density of objects in his brain. Like we use light to see, he uses sound to create a 3D map in his brain. He has trained his visual cortex to process non-visual information. With this ability he is able to ride a bicycle around, effortlessly. Think about riding with your eyes closed. He does it everyday.

According to him, what he does isn’t rocket science. He thinks every one, if trained well, can do it. With a concern for blind people around the world who aren’t encouraged to use echolocation to move around, he started an organization where he teaches people how to do it. You can watch his TED talk here. [video]

Side note: In a Tamil movie, Taandavam, he was the one who taught Shiva to move around using echolocation.

If you think Daniel’s ability doesn’t talk enough about the amazing human brain. This video of David Eagleman talking about how our brain perceives the world, will probably make you appreciate it [the brain] more. Watch it till the end where he talks about these plug-in-brain devices.
In short, brain can learn to interpret various kinds of signals to produce an image.

[read more]

A Bat’s Inverted Sleep Position

by Anupum Pant

I have written about sloths in the past. In that post, we appreciated the way their bodies are engineered to stay inverted for most of their lives. It turns out, a bat’s body is designed (rather evolved) in a similar way, which enables them to relax and sleep upside down. In this post, I would like to discuss – why did they evolve this way and how do they do it?

If you are interested to know more about bats, you will definitely like this post from the archives. [Bats can See]

How can bats manage to sleep like this?

Humans sleep in a horizontal position, cows sleep with their eyes open, horses sleep in a standing position, and of course, bats sleep in an inverted position. What makes an animal sleep in the position they do, is basically their anatomy – the way their bodies are designed. While sleeping upside down might seem as an anomalous behavior to us, it is a normal position for the bat’s body. Like we don’t exert energy when we are lying down, bats’ bodies don’t consume extra energy for hanging down like that.

Firstly, a bat’s claw is like a hook. A better way to understand why this helps is, to look at a converse behavior – the way a human hand works. We use up energy to contract tens of muscles and make up a hook with our fingers; this is not a normal state of our hand. Also, our relaxed hands are open where we don’t exert any energy and we sleep with our hands in that position. A bat’s claws are designed in a completely inverse fashion; they are hooked in the normal position. They don’t take up energy to make them into hooks, they are like that. And they sleep like that – which enables them to hang without using energy.
So, unlike our hands, a bats’ closed fist is their relaxed position. They have to contract tendons and use energy to open them up. This anomalous talon design allows them to hang in a relaxed position.

Bat's Talons - Normal position

Secondly, unlike every other bird, a bat can’t take off from an upright position, or from the ground. They have to be inverted to start flying. This is because they have relatively weaker wings which can’t make them fly from a stationary position. Think of an X-51A Waverider, which has to be carried on a B-52 plane and dropped down to start a flight. They drop down for a very small amount of time and beat their wings vigorously to start a flight. Since, they have to wake up inverted to go flying and catch a meal, they go to sleep like that.

Why did they evolve this way?

They’ve evolved this way to simply stay away from the predators:

  1. By hiding up in a place where not many predators would look – under a bridge, roof of the cave and dark tree canopies. Also, at places like these, they don’t have to compete with other birds for a place.
  2. And by escaping quickly in case of an attack by attaining instant flight [see above].

Bats Can See

by Anupum Pant

While every teacher around the world is busy teaching their kids that bats are blind, the contrary is actually true. Bats aren’t really blind and they can see pretty darn well even in low light. In fact, their eyes work better than our eyes do in a dimly lit environment (eg. Moon light).

None of the bats’ 1100 species are completely blind. Although, there are a few which depend heavily on a technique called echolocation to navigate around objects which are near, they still have to use eyes to see objects which are far away. Additionally, most bats like to hunt in complete darkness (to avoid competition from other birds), so they use echolocation during such times [because eyes need at least some amount of light to be present]. The daylight hours spent by them to groom or sleep don’t demand much of their visual skills, but that doesn’t make them blind.

One way in which bat’s vision is poorer than our visual ability, is that they can’t see colors like we do. Everything they see is in black and white. This disability, if you may call it one, is compensated by their ability to detect light waves whose frequencies lie beyond the human visible spectrum. Flying foxes, however, which are actually bigger bats, can see colors.

So, simply put, bats can see, but they don’t have to use their eyes to hunt or move around. This makes your teacher wrong when he/she says chides you with the phrase – “Blind as a bat”

Bonus Bat Facts

  1. Bats don’t carry rabies. However, like humans, the disease affects some bats.
  2. Apart from vampire bats found in Mexico, Central America and South America, no other bats suck blood.
  3. Bats hunt insects above your head, they aren’t interested in your hair or your eyes.
  4. Bats can catch insects with their tail or wing membranes.
  5. Fruit bats are also known as flying foxes, they eat fruits.
  6. Bats collectively eat tonnes of insects and protect our crops.
  7. Some bats eat fish and frogs.
  8. Bats’ dung, is rich in nutrients. It is mined from caves, bagged, and used by farmers to fertilize their crops.

Echolocation: A bat echolocates by sending out streams of high-pitched sounds through its mouth or nose. These signals then bounce off nearby objects and send back echoes. By “reading” these echoes with its super-sensitive ears, the bat can determine the location, distance, size, texture and shape of an object in its environment. In some cases, a bat can even use echoes to tell insects that are edible apart from those that aren’t. – [Source]