Science Friday - Unmasking Owls’ Mysteries | Why It Feels So Good To Eat Chocolate

Episode Date: December 29, 2023

Unmasking Owls’ MysteriesDon’t let owls’ cute faces fool you—they’re deadly predators. This duality is part of what makes them so mysterious to humans. And their contradictions don’t end there: Their hoots are among the most distinctive bird sounds, yet owls are nearly silent when gliding through the air to catch their prey.Scientists are learning more about why owls are such good predators—how their hearing and night vision are so sharp, and their flight so silent. With new technology, researchers are also decoding owl communications, increasing our understanding of their social structures and mating habits.John Dankosky talks about all things owls with Jennifer Ackerman, author of the new book, What An Owl Knows: The New Science of the World’s Most Enigmatic Birds.Why It Feels So Good To Eat ChocolateWhen you eat a piece of good chocolate, chances are you don’t just bite down and chew away. There’s a good chance you hold the chocolate in your mouth for a moment, feeling the silkiness as it softens, melting into a molten mass and mixing with your saliva. That gradual phase change process—as fats in the chocolate melt from solid to liquid—is a big part of the chocolate mouthfeel experience.Researchers at Leeds University in the UK have constructed an artificial tongue that doesn’t focus on the taste of a food, but rather its texture, and how that texture changes over time. Using the artificial tongue, they explored the textures of materials that can change phase in the mouth, such as chocolate, butter, and ice cream. They reported their findings in the journal ACS Applied Materials & Interfaces. The researchers found that in dark chocolate, the sensation in the mouth is governed largely by the fat content, as the surface of the chocolate begins to soften. A few moments later, as the chocolate melts completely and mixes with saliva, the fat content of the treat is less important to the mouthfeel experience.Dr. Anwesha Sarkar, an author of the report, joins Ira to talk about the research, the challenge of designing a lower-fat chocolate that might exploit these findings, and the importance of learning about textures to determine why people like—and don’t like—certain foods. Transcripts for each segment are available on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Ever wonder why it feels so good to pop a piece of, say, I don't know, holiday chocolate in your mouth? Most of the aversion for food, if you think of, or liking actually comes from texture, which is much, much less studied. We always say about taste, but food is much more than that. It's Friday, December 29th, but you know, it tastes just like Science Friday. I'm SciFri producer Shoshana Bucksbound. A piece of good chocolate melting in your mouth is one of life's. greatest pleasures. Coming up, we'll talk with a researcher who created a sort of artificial tongue to better understand the friction required to taste a tasty piece of chocolate. But first,

looking at the science of owls, here's Sifarize John Dankoski. I love these birds. I find the mysterious. In recent years, too, I've been seeing a lot of them in the woods near my house. I love how they can just hunt so silently, but also make really distinctive sounds when they want to be heard. I love having them watch me from the trees. I could go on forever, but needless to say, I really, really love owls. And scientists are learning a lot more about why they're such good predators, how they're hearing and their night vision is so sharp, and how their flight is just so quiet. So here to talk more about all things owls is my guest, Jennifer Ackerman. She's the author of a new book What an Owl Knows, the new science of the world's most enigmatic birds. She's based in

Charlottesville, Virginia. Jennifer, welcome back to Science Friday. It's such a pleasure. Thank you for having me. The hoot of the owl is probably the most recognizable bird call that we have, but it's not just hoots that owls make or shrieks. They've got a very sophisticated form of communication. What have scientists learned about how owls communicate? Yeah, well, they've learned that a hoot is not just a hoot. It's one of the really delightful surprises I learned in my research. Al's have very elaborate vocal repertoires that are really teeming with meaning. You know, they have greeting hoots and territorial hoots and emphatic hoots. And they don't just hoot. You know, they chitter, squawk, squeal, and their different calls communicate really highly specific information about their sex,

their size, their weight, their individual identity, and even their state of mind. And decoding some of these vocalizations using machine learning has revealed something pretty interesting that owls might not be as monogamous as we thought? It's true. And the way we've learned this is that it turns out that adult owls have highly distinctive voices, and they can actually recognize one another by voice alone. And now we too can identify individual wild owls living in the woods by these unique territorial hoots. And that means two things, that researchers can actually monitor these owl populations more accurately. And that is a really important tool for conservation, but also they can actually observe by listening who's mating with whom

and whether couples are in fact staying together. And, you know, the wisdom had been that most species of owls were monogamous, you know, pairs made it for life. And it turns out to be not so, you know, to the great surprise of scientists, there's often so much mate switching among the owls they're monitoring that it's hard to keep up. There are so many distinctive owl species. and you talk about so many of them in your book. I want to talk about a few of them. And we'll start with the Great Grey Owl, this kind of iconic bird. It's really impressive when it comes to its hearing.

And one of the facts in your book that fascinated me the most is that they're able to hear a vol scurrying under a foot of snow. How are they able to do this? Yeah, this is this was the thing that just blew me away about a Great Grey Owl is, you know, they can from the air, they can hear a vole or a mouse tunneling under as much as 18 inches of snow. That's just so remarkable. It was really almost four or five decades ago in the 1960s that the famous biologist Roger Payne, you know, he showed that an owl can actually catch a mouse in the pitch black relying only on sound. And it turns out, you know, owls that hunt by ear like barn owls and great gray owls,

Their heads are really just designed for listening. They have these big facial discs and that act like a kind of big feathered external ear. It's kind of like a satellite dish for collecting sound. And this facial disc channels the sound toward their ears. And it's what's inside those ears that's really so remarkable. And scientists have begun to tease apart lately that they describe an owl's inner ears as the race cars, the Ferraris of sound sensitivity. And it's true, you know, the owls have these really big cochlea.

They're the hearing organs in the brain. In a bird like the barn owl, like the cochlea is just crazy long. It's like three or four times as long as the cockley of most other birds. And that gives barn owls, great gray owls, a sense of hearing that's really almost unequaled in the animal world. So they're very sensitive to sound. They hear very well. But what makes them such efficient predators is they, Then they don't make any noise.

Prey can't hear them coming. Even the most silent predator birds, other than owls, you can hear them flapping down. What is it about owl's wings that make them so silent? Yeah, it's really, I think it's one of the great wonders of the bird world is an owl's quiet flight. And they can fly quietly in part because they have what's called low wing loading. And that's that their wings are very big in relation to their bodies. So their flight is very buoyant and slow. But it's also because of the really ingenious design of their wings and feathers,

which kind of squelch the normal sounds that bird wings and feathers make. Owls have three really remarkable features that hush their flight. And they have this, it's called a comb, a row of really fine hair-like bristles that kind of extend forward along the leading edge of the wing, where it meets the oncoming air. And when the air hits that comb, the serrations and those little bristles, they break up the turbulence that normally causes a lot of noise on a bird's wing. And that effectively suppresses the kind of swish sound that usually is made by a bird's wing. And then they have a little row of wispy vein fringes on the rear edge of the wing that serves a similar function.

And then this is the really cool thing. They have this soft layer of velvet that coats. the feathers in the whole wing. And that silences any kind of rubbing together noise that the feathers might make in another bird. Now, owl's eyesight is also pretty different from other birds. How is it different? For one thing, they have eyes that are really big for their body size. If our eyes were in similar proportion to our bodies as an owl's eyes are to its body, they'd be about the size of an orange and weigh almost four pounds. So owl eyes are super big. They're also tubular and they're rigid and locked in their sockets in a kind of forward gaze like ours are.

Their forward-facing eyes gives them binocular vision, which is a really big advantage in in zeroing in on moving prey the way they have to. But, you know, also having your eyes locked in place that has consequences. You know, aisles can't move their eyes. So they actually have to move their heads to keep something in sight. It's a myth that owls can actually rotate their heads full circle, some species can turn their heads almost three quarters of the way around, which is like three times the twisting flexibility that we humans have. I'm John Dankosky, and this is Science Friday from WNYC Studios. Let's talk about another iconic owl species, and this is a little owl, burrowing owls,

and I want to hear where they live and what they do, but could you first describe a burrowing owl for someone who's never seen one before? Yeah. Well, They are just the most comical, kind of adorable little creatures. They're just heads on long, stilt-like legs, and they have this habit of kind of cocking their heads in curiosity. They're very cartoon-like and human-like at the same time. First of all, they live in 24 countries in North and South America, so they're very widespread in the new world.

And they nest underground in boroughs that are dug by, oh, prairie dogs, woodchucks, scoes. dunks, badgers, armadillos, and sometimes even under human-made structures. You know, I've seen them nesting under piles of debris or like a little openings beneath pavement. And one of the really cool things about these little owls that I learned in researching the book is they actually decorate the outside of their burrows with all kinds of stuff, all kinds of treasures. You know, stuff like dung, bison dung, or coyote scat. They, they, they, they, They decorate with bits of wood, bones, moss, and swatches of fabrics, kind of like whatever they can find.

And they actually have preferred colors of things. They like red and white over blue and green, for instance. But what was interesting to me is that all this decorating isn't about mate attraction or courting the way it is in some birds. Because the male only begins decorating after his mate has started nesting and laying eggs. and the decorations are really meant to convey to other males that the burrow is occupied. So a male is saying, you know, don't mess with me. I own this place. Look at all this stuff I collected. The researcher who studies these birds, David Johnson said to me, if you want to show you're a tough guy in the world of burrowing owls, decorate.

I just love that. I mean, who knew? So you've gotten to meet quite a few owls in person. What's it like to be near an owl to get up close and personal and actually see it doing its owly things? Yeah, I think the most exciting experience for me was I was in the field in western Montana with Denver Holt, who's I think he's considered probably one of the world's foremost experts on owls. And I had the opportunity to hold one of these. It was a long-eared owl. and it was just an incredible experience because her legs were these big, strong legs, these killer talents, you know, tucked between my fingers.

But her wings were, you know, soft as rabbits' fur. And that was the thing about owls, you know, they're just, they're ferocious and also they're sort of soft and tender. This owl was incredibly cute, but also like a brutal killer. This bird, she kind of locked eyes with me in this cat-like stare. And I just felt like, you know, there we were eye to eye, creature to creature. And it just felt like such a powerful connection, you know, both of us questioning, what are you? What are you thinking? What are you feeling? And I, you know, I just held her for a while and marveled at how how beautiful she was and how superbly adapted to her world, really so quiet, so skilled. It was really an amazing experience. They really are remarkable animals. Jennifer Ackerman is the author of What an Owl knows. The new science, the world's most enigmatic birds. She's based in Charlottesville, Virginia.

Jennifer, thanks so much for the book and for bringing us all these great stories. Thank you so much for having me here, John. It's been a delight. And if you want to read an excerpt of the book, go to Science Friday.com slash owls. I don't know about you, but for me, at this time of the year, it's hard to get away from the snacks. holiday cookies, maybe that special sourdough bread, a glass of eggnog, and a lot of chocolate, hot chocolate, fancy candies. Well, go grab a piece right now if you have one,

because for the rest of the hour, we're talking about how chocolate makes you feel. And no, no, no, I'm not talking about loved or happy, but the actual physics of how it feels in your mouth, because that's part of the secret of enjoying chocolate, isn't it? Joining me now is Dr. Unwishis Soccer. She's a professor of colloids and surfaces at the University of Leeds and Leeds UK. Her group recently wrote about this phenomenon in the journal ACS applied materials and interfaces.

Welcome to Science Friday. Thank you so much, Ira, for having me. You're welcome. Now, I know your team developed a sort of artificial tongue, not so much to taste the samples, but to investigate the feel of the food. Exactly. Do understand the friction. What happens in the mouth?

much more from a textual perspective. And why is that important? So, you know, most of the aversion per food, if you think, or for liking actually comes from texture, which is much, much less studied. We always say about taste, but food is much more than that.

So we develop this tongue to really understand the physics, what goes on in the mouth when you rub a food against the surface, and chocolate happens to be the fun material to work with. All right, let's get right into that. If I take a bite of chocolate, what's going on with the chocolate in my mouth? With the premium chocolates, what do you do?

So you just don't chew, chew, chew. You put it in your mouth. Either you lick it against your tongue, like appreciate the feel. And then gradually and gradually it starts melting in your mouth. So it's a face change material. So it melts in your mouth. But this whole process happens in a couple of seconds. So what we did in our study was to understand this process.

to dissect this few seconds into exactly what happens in the mouth. So when you put the chocolate in your mouth, when you rub it against your tongue, when it mess, when it mixes with saliva, what are the exact things that goes on? And why, for example, fat matters, does it matter, the content of fat and so on? Well, tell us, what did you find happening? What happens? Take us through the steps of what's going on in your mouth with the initial feel and then the melting and so on. So what we did is we took that chocolate as a model and then with different fat content and then we rubbed it against this artificial time.

And what we realized was very interesting. So when you take the chocolate in your mouth, which is the first step, that is where it matters the most the calorie content. That we see there is a very interesting difference in. friction between a 70% fat chocolate versus a 90% fat chocolate. But after that, when it has started melting and mixing with saliva, it's actually saliva drives the game. So you don't see so much of the calorie content affecting. Of course, you need those fat to create the feel, but it matters less as compared to the initial touch. Hmm. So if I wanted to optimize that silky

feel, would I front load the fat content into the surface of the piece? In principle, yes, exactly. So there it matters way more to think about the silky malt field, to think about the right texture of what you create for, whereas in the body, it matters less. As maybe the protagonist, there is much more saliva-driven rather than the fat-driven. Now, I know that you did not invent a new chocolate. Your work was done using off-the-shelf chocolate samples from the store. door, but how easy would it be to engineer a chocolate with the properties that you would like?

Is it as simple as have a low-fat piece, then dip it in a shell of fattier stuff, or how difficult is it? Yeah, that will be the obvious one, isn't it, to create a clear kind of material. But, you know, if you look at the history of chocolate making, it will be difficult because it is made from cocoa beans and stuff and a lot of flavoring material come in that picture. But if you see how food manufacturing is involving, we have 3D printing now. So there are a lot of things that's going on in terms of the technology. So imagine the situation where we are printing our chocolate in the way we want at our hole. So that is the kind of, you know, utopia it seems like at the moment, but it's not.

Like in few years down the line, we will have that. And we have that actually in manufacturing in many countries. The other thing to think about is that there are also a lot of chocolates which are not made with cocoa butter like composites and compound pad, vegetables, fat, and so on, where we can make a lot of changes in the process to make those kind of chocolate, which has a much more outer surface layer of pad versus inner. But again, I want to stress we did not make a chocolate. So it would be an interesting challenge to take, of course. If mouthfeel, as you talk about it, if the texture is so important for that first bite of food,

Does your tongue know this? Is it especially equipped to feel the texture as well as taste it? So this is very interesting, you know, so if you think of the tongue, it's a muscular material, but it has a lot of features. And if I make it very simple, you have fungiform papilli which contains taste pot and the filipol papillian pappily, which does not contain any taste part. And they are much more numerous in the number. So these features in the mouth, they are just there for. for speech and for friction and for detecting texture. So how cool is that?

That is cool. So I think alone and studies needs to be there in this area to understand texture and how does texture contribute to liking of food? We know it does contribute to disliking. People don't like, you know, mushy material, for example. It's all linked to texture rather than the taste. It can still be sweet, but the texture matters. Are there other foods that this research applies to as well?

So we said it will definitely the mechanisms which we propose will apply to face change materials like ice cream, like cheese and so on. But we need more work to understand whether it can be applied to other section of food, which is non-face change material as well. But at the moment, we have only looked at face change material like chocolate or ice cream, which contains some amount of fat as a key ingredient. That's crazy to learn that most of the papillet in the tongue have no taste buds, but are there for touch. So if we know this now, and our listeners have that piece of chocolate that I asked them to get, and they want to try this for science, how should they taste their chocolate sample? So they should taste their chocolate sample like the way it is, but just close your eyes and don't think about sweetness means. Don't say it's just sweet.

That's the last thing I want to hear. You want to hear how it feels. Exactly. That's correct. Dr. Sarker, thank you for joining us today. Thank you very much. Dr. Unwichas Sarker, she's a professor of colloids and surfaces. Yes, that exists in the School of Food Science and Nutrition at the University of Leeds in Leeds, UK. That's it for today.

A lot of folks help make this show happen, including Danielle Johnson. Jason Rosenberg. Lois partially. Ariel Zitch and many more. Next time we'll tackle a tough philosophical question. Is math real? We'll see you next week. I'm SciFri producer Shoshana Bucksbaum.

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