Jumping jacks

Had been to Konkan for a vacation last year. It was a beautiful winter morning. At a point in the ghats, we stopped at a tea stall to enjoy the view with a glass of hot chai.

As we chatted with the chaiwalla, he told us the story of the fisherman who saw dolphins in the sea a few years ago. As this news spread, these dolphins became a tourist attraction. Now, many launches are available that take tourists into the sea to see these animals of titanic fame.

We decided to go too! The sea was rough, and the boat rocked. But we continued undaunted. The boatman pointed out into the sea. And lo and behold – we could see a dolphin jump out of the water and back into it….several times. Oh! What a beautiful sight!

But have we ever wondered – what makes these ‘fish’ come out of water?

And not only dolphins, even whales show this behavior. Why?

The answer lies in the basic fact that dolphins and whales, although often mistaken to be, are not fish. So, unlike fish, they do not breathe underwater through gills. They are mammals, and like humans, have lungs for breathing. They do not take in the oxygen dissolved in water, like fish. They breathe oxygen from air.

We cannot hold our breath underwater for a long time. We have to come to the surface of water to breathe in again, unless we are carrying oxygen cylinders. Similarly, the dolphin comes to the surface of water to breathe air through a hole on its back that functions as a nostril. It takes in sufficient amount of air into the lungs and goes underwater again. It can stay underwater for about fifteen minutes. Whales breathe the same way, but some of them can remain underwater for upto an hour!

But doesn’t the water enter the lungs of these animals and choke them? No – at the base of their breathing hole, they have a flap which closes as they dive. This flap keeps the water out of the lungs. Also, as they go deeper, although the pressure of the surrounding water increases, their lungs collapse, and the water is kept out.

Further reading:

1. http://library.thinkquest.org/17963/respiratory-system.html

2. http://understanddolphins.tripod.com/dolphinblowholeandbreathing.html

3. http://www.youtube.com/watch?v=S6hNWZQeFzc

  

In the dark

The streets of Gotham were pitch dark because of the power cut. It was almost midnight. Tom could barely see a few feet ahead. As he turned the corner, he became aware of someone behind him. The footsteps came closer and closer, and before he knew it, someone nabbed him by the throat, and threw him on the floor. The masked man pointed a knife at him and began searching him for his wallet. Tom lay helpless on the ground, too scared to react.

Suddenly, something swooped down and pushed the robber over. The figure in the dark started bashing the robber. Thankful, Tom got up to his feet. He wondered who his savior was. And then, he saw the savior’s outline in the dark. It was none other than batman himself!

Of course! Who else could have spotted danger in the dark!

Yes. Bats are nocturnal .i.e. they rest during the day and hunt at night. But how do they find their prey in the dark? The do it using a special ability called echolocation. As bats fly around in search of prey in the dark, they produce sounds by clicking their tongues or contracting their voice boxes. These sounds are very high-pitched, and cannot be heard by humans. These sound waves travel through air. When they hit a flying insect, they bounce off the insect, and start travelling back towards the bat. Using its ears, the bat detects these reflected waves and knows where the insect is.

The bat knows if the insect is on its left or right depending on which ear the waves reach first. It can also make out the size of the insect depending on the loudness of the echo. A smaller insect will reflect less waves, giving a softer echo. On the basis of the pitch of the echo, the bat knows in which direction the insect is moving. An insect that is moving towards the bat will give a higher pitched echo than the original sound, whereas an insect moving away from the bat will give a lower pitched echo. The bats mind unconsciously interprets this information, the way we humans unconsciously interpret the information from our eyes or ears as sight or sound.

The bat can also use this ability to locate stationery objects, and hence to find its way in the dark.

Further reading:

1.http://www.batcon.org/index.php/all-about-bats/intro-to-bats.html

2. http://www.youtube.com/watch?v=gZxLUNHEmPw