Utsuka — U, Jigyasa — J
Transcripts with Timestamps
Both- “Hi Everyone”
U- I am Utsuka
J- I am Jigyasa
Both- And you are listening to IndiaAsksWhy
U- A science podcast supported by IndiaBioScience
J: Where we do the research for you to get smarter.
U: Join us, as India becomes more curious,
Both: one question at a time!
[0:37] J: We all have visited zoos, haven’t we? Utsuka and Jigyasa, on their recent trip to the Zoo, were fascinated to see tigers. While admiring the tiger’s beauty, they realized something. All tigers have stripes. In this episode, Utsuka and Jigyasa explore why tigers have stripes. To know more about the purpose of stripes on tiger’s bodies, they speak to Mihir Trivedi, a wildlife biologist from CCMB.
[1:22] J: “Ooooo…the next animal is…P‑a-n-t-h-e-r‑a tigris, wait that’s a tiger!”
U: Yeah! It is a tiger. They are so majestic. And look at the beautiful stripes — the alternating blacks and oranges!
J: Oh, there are two big ones and one tiny cub in between them!
U: Look over there, that’s a white tiger with black stripes. I wonder why all tigers have stripes?
[Type set sound]
[2:06] J: It seems like Utsuka, scientists are also curious about the tiger stripes! Although they still don’t know the exact reason, there are multiple speculations about their stripes. First, let’s get some basics right. There are 2 different color pigments in the tigers’ skin cells: the brown or black pigment- Eumelanin, and the yellow or red pigment- Pheomelanin.
[2:33] U- Melanin, that sounds familiar. Maybe I heard it in my science class. Don’t they give color to our skin too?
[2:44] J- Exactly, that’s what we are talking about. They do give color to our skin. There are skin cells in our body, called melanocytes, that produce melanin. In tigers, there are some melanocytes that produce Eumelanin, the black pigment, and others produce pheomelanin, the yellow one.
[3:05] U: So, a tiger has black stripes wherever melanocytes produce eumelanin and has orange skin wherever the melanocytes produce pheomelanin, right?
[3:18] J: Yes, you are right Utsuka. Exactly.
[3:22] U: But Jigyasa, I wonder, how do the melanocytes know where to make the dark pigment and where to make the orange?
[3:30] J: Ummm.. so Utsuka, you Remember we saw a tiny tiger cub in the zoo? U: Yes, yes I do! J: It looked exactly like the Mumma tiger, right? U: Yes it did. It had a stripe pattern similar to Mumma tiger.
[3:48] J: Exactly, so can you now recall from your science book, why baby tigers look like their parents? I will give you a hint- it’s the same reason we look like our parents.
[4:00] U: Umm…Let me think … [swoosh music] is it because of genes?
[4:04] J: You are absolutely right! Yes, genes. There are a lot of genes in every cell of an organism’s body. Genes are parts of the DNA that carry information to make you ‘you’! That’s why they are called the blueprint of our body.
[4:19] U: So, you mean that there are genes in the tiger’s melanocytes, the type of skin cells producing pigments, that tell them to make different pigments in different places?
J: Yes! You are getting very close to the answer. Genes produce proteins that help the melanocyte make melanin.
[4:38] U: That means genes in the tigers’ body direct the melanocytes to create the stripe pattern?
[4:47] J: Bingo! Various scientists have tried to study tigers’ DNA. After lots of research on the cat family and tedious analysis, they have identified multiple genes that may play a role in directing pattern formation on tiger skins.
[5:05] U: That’s interesting! Tell me more!
[5:11] J: There are basically two sets of genes that control the process of stripe formation in tiger skin.
[5:17] U: Oh, you mean genes also work in teams?
[5:20] J: Yes, the first set controls the planning for making the stripes and the other set controls the execution of the plan. We can compare this work to making a building. The architect gives the plan and the masons execute the plan.
[5:38] U: Okay, can I guess what their functions might be? Planner genes do the job of laying the foundation of the pattern. The executor genes work to make sure that the melanocytes produce the right kind of pigment according to the pattern. They are like the overseers of melanocyte production. But Jigyasa, when does all of this happen? Like at what stage of tiger development?
[6:06] J: The planning happens before birth, Utsuka. The planner genes decide where the pheomelanin-producing cells and eumelanin-producing cells will sit. Once this is done, the executor genes indicate melanocytes to start producing the pigments assigned.
[6:26] U: That’s interesting! So is it possible that the stripe pattern starts to appear on the tiger’s skin even before birth?
[6:36] J: Yes Utsuka. and that’s why tigers are born with the stripes on their skin.
[6:40] U: Again, this was super interesting! I wonder what good the stripes do for the tigers? What is the purpose of having these stripes on their body?
J: Let’s ask Mihir!
[6:56] Transition music
Phone ringing sound
[6:58] J: Now, It’s time to ask a scientist
[7:22] J: Why do you think Tigers have stripes? What is the role that stripes on a tiger play?
[7:28] M: Tigers, mainly are the apex predators. So of course they don’t have to fear something. They don’t have stripes to hide from other predators but they have stripes to hide from their prey so that they can hunt. They can go insidiously, and then can pounce upon their prey without being seen. Additionally, most prey of tigers like ungulates, deers, and buffalos.. these animals are color blind. The stripes help the tiger to confuse them about where the tiger is and where the bushes are.
[8:02] J: Oh, what do you mean when you say colorblind?
[8:05] M: So, Human eyes are like RGB, red, green, and blue, and we can see in these. But most ungulates can see only in two colors, maybe green and blue. So they won’t be able to associate the orange color that we associate with the tiger.
[8:23] J: Oh! Then my question is, “How do you study these wild animals? Because, you know, they are wild animals, we can captivate them in the zoo but we cannot study the wild properties of the animal in a zoo, Right?.”
[8:40] M: Okay, yeah. So, if you see wildlife biology it can have various aspects to it – some are observational aspects and some are experimental aspects. So, observational aspects would be like behavioral studies, where you go there and you may have camera traps. You will see how Tigers behave and record that. Or maybe you will just observe. You will sit around in the forest and observe various animals and think about how that is happening and then you come to a conclusion. Experimental aspects would be, as I was talking about DNA to extract something like DNA by their blood samples, or what I use, we call non-invasive sampling. Like we use fecal samples, urine samples, or hair samples. So of course, blood samples and tissue samples are difficult to get from wild animals.
[9:31] U: Okay, so, um, so you mentioned you collect these, samples of fecal matter, urine, and all of that. So I’m curious about what a day in your life in the field looks like. Like, what do you do? Can you talk a little bit about that?
[9:45] M: For some amount of time, you have to live in the forest – like, forester, who has their huts or small, small rooms. So you go and live there.
[9:58] J: Wow. Like who knew scientists stay in forests as well.
[10:05] M: Yeah, so that’s a perk of being a wildlife scientist.
[10:08] U: Yeah, so Mihir did you always envision yourself becoming a wildlife biologist? Like, did you as a child think that one day you would be?
[10:20] M: My answer would be slightly unconventional. I never dreamt of becoming a wildlife biologist. So my basic interest was in genetics. I first studied genetics in my 11th class. So in 11th class, we had a CBSE course, NCERT book. So in the NCERT book at that time, the first sentence of the genetics chapter was, ‘have you ever wondered that two elephants only give birth to elephants? Why don’t they give birth to dogs?’ That actually struck me. That has struck with me since then. Why do you find it so obvious that humans are giving birth to humans only and dogs are giving birth to dogs only. What actually makes it? It came from there that there are genes., Then, there is a development process and how does the development process actually develop? It came from evolution. From molecular biology, we can understand how things work. But the reason for everything is evolution. I found out that why is much more difficult to answer than How. And I am kind of that History buff also. So Biology has this unique thing that Biology has a history also. So evolution looks like a marriage of both the things which I like. I like history, so evolution has that. I like biology, and evolution is also that. So yeah.
[11: 45] J: So what would you like to say to all listeners who may be interested in that first paragraph or may have that curiosity?
[11:56] M: One obvious piece of advice would be to read as much as you can and read eclectic studies, have a varied bunch of reading, different things. Reading takes effort. So it gives you time so that you can develop your own thinking. And another thing which I would emphasize is that slightly unconventional embrace the confusion in your life. If you are confused about whether you have to choose physics or biology, okay accept it. Having confusion is a very nice thing to have.
[12:34] J: So do you now understand why tigers have stripes?
[12:37] U: Yes, the stripes help tigers to blend into the grasses to hide from the prey. The black stripes are because of eumelanin and the orange skin is because of pheomelanin. Melanocytes are the type of skin cells that produce these pigments. And to control this pigment production, there are two sets of genes in the tiger’s cells. One set lays the foundation and decides which melanocytes produce what kind of pigment. The other set executes the pigment production.
[13:15] J: We also got to know that a sentence in the science textbook eventually inspired Mihir to become a wildlife biologist. And How cool it is that he gets to live in the forest studying animals in the wild!
[13:30] U: As we always say, we are still learning a lot about tiger stripes and patterns on animal skin in general.
[13:40] J: But we’re sure that our conversation must have sparked interest for you to become the next tiger researcher! Right, Utsuka?
U: Absolutely, Jigyasa!
[13:50] J: Follow us on our social media and let us know if you are interested to know more about tigers of different colors
[14:02] U: So, that’s it for today. We would like to thank Mihir Trivedi for being a part of this episode.
J: If you want to know more about today’s scientists, check out their profiles. Link in the Show Notes!
U: If you have any questions shoot them away to Indiaakswhy@gmail.com
J: If you’d like to directly talk to us and join the fun, join the fun on our Telegram Group. Link in the show notes.
U: For updates on IndiaAsksWhy, follow IndiaBioScience @IndiaBioscience on Twitter, Instagram, Linked In, and Facebook! (link in the show notes as well!)
J: Shweata N. Hegde and Ruchi Manglunia are the hosts of the podcast
[14:43] U: Ira Zibbu helped us transcribe and design the interview segment.
U: And we are thankful to IndiaBioscience for hosting us.
J ‑So stay tuned and stay curious!