The Best Tail For Balance | Bindi Irwin Wants Kids To Become ‘Wildlife Warriors’

The bone and joint structures in mammal tails help them keep their balance. Could those benefits be adapted for robots? And, in her first children’s book, conservationist Bindi Irwin takes little readers on a journey through Australia Zoo.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Speaker 00

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• 0:14Flora Lichtman?

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• 1:04Flora Lichtman?

  This is Science Friday. I'm Flora Lichtman. Today on the podcast, why tails are underrated. But first, a chat with conservationist Bindi Irwin, daughter of The Crocodile Hunter.

• 1:16Speaker 02

  We described Dad as a living hurricane. Like, he was a living hurricane, just stuffed inside a person.

• 1:25Flora Lichtman?

  More than 20 years ago, conservationists Terry and the late Steve Irwin captured the world's attention with their show, The Crocodile Hunter.

• 1:33Speaker 03

  Hey, hey, hey, hey, what's going on here? This croc is going ballistic. Woo-hoo, I can't believe this. Every way I turn my goggles, I can see sharks. Rocky, it was dangerous.

• 1:48Flora Lichtman?

  It introduced millions of people to the Australia Zoo and the strange, and sometimes scary, wildlife from Down Under. Now, their daughter Bindi Irwin runs the zoo with her family and has taken up the conservation mantle. Her new book is called You Are a Wildlife Warrior: Saving Animals and the Planet. In it, she takes young readers on an adventure through the zoo, along with her daughter Grace. Bindi, welcome to Science Friday.

• 2:13Speaker 02

  Thank you so much. G'day, I'm so happy to be here.

• 2:17Flora Lichtman?

  Let's talk about your new book. What made you want to write it?

• 2:20Speaker 02

  Oh, my goodness. I am so excited and so proud of my book. I have to say, this book all came about because of our beautiful daughter, Grace. I held our gorgeous daughter in my arms for the first time and went, oh, my goodness, I can't even imagine the amazing life ahead of her. And here at Australia Zoo, our whole world revolves around conservation. Pretty much, it's not just what we do, it is who we are, our conservation work. And I had a small feeling that our daughter would love wildlife and wild places as well. And of course, we would have supported her, you know, if she didn't, absolutely. But as she-

• 3:03Flora Lichtman?

  How old is she now, Bendy?

• 3:04Speaker 02

  She is three and a half. And as she's grown up, she has only gotten more excited and more involved in all of our conservation work. And boy, does she love animals. It is so beautiful to see. So this book kind of bloomed from there and hopefully inspiring the next generation of wildlife warriors to appreciate and explore our gorgeous mother earth.

• 3:27Flora Lichtman?

  Well, I have a three and a half year old myself.

• 3:29Speaker 02

  Oh, my goodness. So you know, you know, this is a time for-

• 3:33Flora Lichtman?

  I'm in it with you.

• 3:35Speaker 02

  Discovery, big emotions, all the things. Congratulations.

• 3:38Flora Lichtman?

  You too. It is wonderful to see the world through three and a half year old eyes, sometimes.

• 3:45Speaker 02

  Yes, definitely. Whew, wear their hearts on their sleeves, that's for sure. We always say, we never have to wonder what Grace is thinking. She will tell you.

• 3:53Flora Lichtman?

  In the book, you invite your readers to be wildlife warriors. Where did that term come from?

• 4:00Speaker 02

  Well, the term wildlife warriors actually originated from my dad. My dad first created that term and it has just become our family's motto. It means so much to us. Being a wildlife warrior means to stand up and speak for those who cannot speak for themselves and to make a difference for the planet.

• 4:21Flora Lichtman?

  I was watching some old clips of your dad, Steve Irwin, who was just so engaging, of course, to watch.

• 4:29Speaker 02

  Thank you.

• 4:29Flora Lichtman?

  And I was thinking about how he brought this sort of, you know, for lack of a better term, and you might have a better term for it, but this sort of like wild man energy to conservation, like there's shredding guitars and crock wrestling. And I wondered- Whether, you know, that was a conscious choice, like a strategy to bring people into conservation who might not otherwise care about animals or about crocodiles. I don't know. What do you think?

• 4:57Speaker 02

  I do. I do like, wasn't a strategy. I am, I appreciate, I appreciate the question. Thank you. But I have to tell you, that was, that was Dad to his very core. I mean, what you saw,

• 5:12Flora Lichtman?

  That's just who he was.

• 5:13Speaker 02

  What you saw on camera. There was no strategy there. That was a hundred percent him, a hundred percent of the time. Truly, like, he, he was the most passionate. We described Dad as a living hurricane. Like, he was a living hurricane, just like stuffed inside a person. He, he, he was, he was always, always so passionate about everything that he did. And, you know, when, when you're a kid and you see something amazing, you fully embrace it and go, "Grykee, this is amazing!" And get excited about it. And I remember growing up, like, that is who he was. We would wake up in the morning and he, he started his day of work at about, oh, 2:30 in the morning.

• 5:57Speaker 02

  Like, he, he couldn't sleep. He had, he had just so much he wanted to get done. He'd burst through the door in the morning and go, you know, "We're heading out to Windora. We're, we're gonna do research with fear snakes." Or, "We're gonna go climb a mountain." And it's, he, he, he just, he never stopped. And he was so passionate about everything that he did. And truly, what you saw on camera was who he was. And I feel like so many people lose that sense of, of wonder and inspiration and awe for our world. And Dad didn't lose that. Here's something interesting. Dad, we all talk about "live every day as if it's your last", and Dad really did.

• 6:38Speaker 02

  In fact, after he got done doing some incredible wildlife thing that we were often there for, you know, whether it was, you know, feeding a crocodile or swimming with whale sharks, he would go, "Well, now I can die." And, and he, he meant it. He was like, "This was such an incredible moment in my life that if I'm gone today, I, I feel, I feel completely happy and at peace and am grateful for the experience." And Oh my goodness, we all talk about living each day as if it's our last, but we, we should, we should, we should, we should actually feel that sense of wonder in our world and do things that genuinely make us happy. Yeah, I really appreciate that lesson that, that

• 7:23Speaker 02

  he taught me without realizing it, I think. And as I've grown up, I've, I've come to realize it more and more. He, he led by example and I love that about him.

• 7:32Flora Lichtman?

  It is a very powerful way to live and it's also very rare, I think.

• 7:36Speaker 02

  It is, it is very rare. It's very much easier said than done, I think.

• 7:40Flora Lichtman?

  Yes, yes. The book centers you and your daughter. You're speaking to her in it. Has becoming a parent changed the way that you think about conservation?

• 7:53Speaker 02

  Oh, absolutely. It has become so much more important to me. After having Grace, you know, you, you think about this little person and what future they are going to have on the planet. I want to do everything in my power to make sure that Grace and the future generations are going to live in a world with clean air and fresh drinking water and an abundance of wildlife.

• 8:18Flora Lichtman?

  I want to talk a little bit about the zoo and, and just what it's like to live on the grounds, what it's like to run a zoo. Give me a day in your life.

• 8:31Speaker 02

  Oh my goodness. Well, thank you for asking that. It's, um, it is never a dull moment. It is always very exciting. So our family, we live and work within Australia Zoo. It's a family-run business. So we are, we are busy. I will say it is busy. For those of you thinking about running a zoo, you probably won't sleep much.

• 8:55Flora Lichtman?

  Really?

• 8:55Speaker 02

  But that's okay, because you'll be very fulfilled. You'll be like, this is great. Um, no, but in, in all truth, it is, it is wonderful and every day is completely different. The only, my, my dad, this is why my dad was so passionate. The only way you're going to get people to genuinely want to make a difference is first by Showing them what they should be protecting, showing them how a lemur makes the cutest little chewing noises when it eats its food. How an echidna actually has the funniest little like fluff between its little spiky quills. And all of these, all of these things that, you know, you wouldn't, you wouldn't know about if you just read about it in a book.

• 9:39Speaker 02

  And what, oh my goodness, what an experience to watch people like. I have, I have taken a lot of people on many tours of Australia Zoo and watching people genuinely connect with an animal to see that light in their eyes as they realize how amazing it is to have a meerkat standing on your head. And then their questions leading on from that, how can I help protect meerkats? How can I make a difference for them? It is truly inspiring, but gosh, Australia Zoo, you have to come visit us now. Please come see us.

• 10:10Flora Lichtman?

  I'd do anything to see a wombat, I have to tell you.

• 10:13Speaker 02

  I can make that happen. They are so fun. Trust me, as long as you have a sweet potato, the wombats will be your best friends.

• 10:19Flora Lichtman?

  Great, all cotton and my pockets are going to be stuffed with them.

• 10:21Speaker 02

  Yep.

• 10:22Flora Lichtman?

  Bindi, thank you so much for joining me today.

• 10:24Speaker 02

  Thank you. It has been so lovely to talk to you and I feel like you guys are helping people to accidentally learn something along the way, which is just brilliant.

• 10:33Flora Lichtman?

  That is our goal. We want to help people accidentally learn things every week. Bindi Irwin is the author of You Are a Wildlife Warrior, Saving Animals and the Planet, and a conservationist at the Australia Zoo.

• 10:48Flora Lichtman?

  After the break, why tails are great and why a better tail could make a better robot. I just think there's more to the tail than we've been giving it credit. They're more than just a little fluffy thing. Stick around.

• 11:05Speaker 00

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• 11:24Speaker 00

  Science delivers harvests that feed families, tools that help farmers grow more with less, and new ways to protect land for generations to come. Let's keep asking, keep testing, keep discovering, so science can keep delivering. Learn more at sciencedelivers.com. Support for Science Friday comes from the William K. Bose Junior Foundation.

• 11:49Flora Lichtman?

  It has been a busy news week, and we're going to start out with some counter-programming. We are talking tails. If you have ever met a cat, you've probably at some point been amazed by how acrobatic they are. They can reorient themselves effortlessly, even in midair. It turns out that a lot of that twistiness comes down to having a top-tier tail. Writing this week in the journal Royal Society Interface, researchers explore the mechanics of different tails, from reptiles to mammals, and consider how a better tail could help build a better robot. Joining me now to untwist all of this science are Dr. Talia Moore, Assistant Professor of Robotics and Mechanical Engineering at the University of Michigan in Ann Arbor, and Dr. Carrie Weber,

• 12:34Flora Lichtman?

  a postdoc in Kim Cooper's lab in the Department of Cellular and Developmental Biology at UC San Diego. Welcome to you both to Science Friday.

• 12:43Speaker 04

  Thank you. I'm so thrilled to be here.

• 12:45Speaker 05

  Hi, I'm happy to be here.

• 12:46Flora Lichtman?

  Talia, you're a roboticist. Why do you care about tails?

• 12:50Speaker 04

  Yeah, tails are just a multifaceted appendage. You can do a lot of different things with your tail than you can with your legs. And so it just kind of gives you this like extra oomph, a little pizzazz to the things that a robot can do.

• 13:06Flora Lichtman?

  Carrie, you're a developmental biologist. What do tails mean to you?

• 13:11Speaker 05

  I love that tails can be looking so different and do so many different things, but they have a really shared, similar embryonic origin. So they're kind of made the same way. They happen at the same point in development, whether it's a human, or a cat, or a mouse, or a giraffe. But they all look really different. They're different sizes. Their vertebrae are different shapes. And I just am mystified by how evolution and ecology and genetics can make this organ look so different.

• 13:41Flora Lichtman?

  You're mystified by the mystery of the tail.

• 13:43Speaker 05

  I am.

• 13:44Flora Lichtman?

  It's not a mystery I had ever considered, I have to say, until this paper. So, thank you for giving me something new to think about. Talia, what did you find with this new study?

• 13:54Speaker 04

  In our paper, we have a simulation environment to try and understand how tails can be used as inertial appendages. And the way I like to explain that is if you're a tightrope walker and you're walking on your tightrope, you have this really long stick. And if you start to lose your balance, you rotate that stick and it kind of rotates your body so you can get back onto that tightrope. And that stick is your inertial appendage. And a paper that I wrote a while back showed that lizards can do this with their tail to rotate their body when they're jumping in midair. And that tail, we modeled it as a single rigid rod.

• 14:36Speaker 04

  And that inspired a lot of robots, but they've all been kind of single rigid rods moving in one plane.

• 14:42Flora Lichtman?

  Which is not actually true for many tails, right?

• 14:45Speaker 04

  Right. And so, we started looking at mammals and seeing, wow, their tails, they're making all these complex curves in 3D space. And we started to investigate, what if the joints in the tails and the curve of the tail is actually what's helping these tails act as better inertial appendages, even though they're skinny and don't have the moment of inertia themselves? So, we did this simulation to try and compare the effectiveness of different types of tails, which has never been done before. Is this shape of your tail better than this shape of your tail? And going to be able to move your body more effectively? So, we came up with this optimization program.

• 15:30Speaker 04

  And then, once we figured out that joints were really helpful, then we said, okay, what if we allow the bones to change size, but the total tail length to be the same? And so, when we did that optimization, we actually found that the, there's like this really sharp crescendo and then a sharp day crescendo. So, the bones get a little bit longer and then they get shorter.

• 15:54Speaker 05

  And when we look at the real tails that Carrie shared with us, we find that animals that use their tails as inertial appendages have that exaggerated crescendo, decrescendo, more than the tails of animals who don't use their tails as inertial appendages.

• 16:13Flora Lichtman?

  Okay, so where the tail attaches to the body, the bones are short, and then they get longer, and then they get shorter again.

• 16:18Speaker 05

  Exactly.

• 16:19Flora Lichtman?

  Carrie, after all these simulations, I mean, you were in the museum archives, tail spotting.

• 16:25Speaker 05

  Yes.

• 16:26Flora Lichtman?

  What were you looking for?

• 16:28Speaker 05

  So I had also noticed this crescendo pattern in mice and the rodents that we study in the laboratory. And I wanted to know if this pattern was in all mammals. And so I was just a menace, measuring as many tails as I could get my hands on in the museum archives. And then we were talking with Talia about this paper because we'd already been collaborating and talking about tails. And it was really, really exciting to find that they had found this pattern in the simulations and I was finding these patterns in the museum archives. But it turns out there's lots of different patterns and we don't know what those patterns do yet. And we're really excited to figure it out.

• 17:04Flora Lichtman?

  Carrie, what, in your opinion, what is the top tail in the animal kingdom? The tail of all tails?

• 17:11Speaker 05

  I can tell you my personal favorite, which is the silky anteater. And that one stands out because most of the tails that we've measured, the complete ones, average out around like 30 vertebrae. That tends to be what most of them are making, whether they're prehensile or they're using them for inertial maneuvering. But the silky anteater tail that we measured had 41 vertebrae in it, which it's the longest one in our dataset. I remember when I pulled the skeleton out of the box, I was in awe of how many vertebrae

• 17:39Flora Lichtman?

  Did you gasp?

• 17:40Speaker 05

  are in the tail. I did, I did gasp. But it's a very cool animal. It's an anteater, but it's mostly living in trees and it has a prehensile tail. So in pictures of it, you can see it grasping and holding on to branches. It's very cool.

• 17:53Flora Lichtman?

  So Talia, should we expect robots with anteater tails? Like, is that what you're thinking?

• 17:58Speaker 04

  Yeah, I think there are some folks who are working on prehensile tails right now. I saw one at a conference last year. And so I think they're closer than you think.

• 18:09Flora Lichtman?

  Really? I mean, a robot with a tail sounds creepy to me.

• 18:13Speaker 04

  There are actually a lot of robots with tails that are out in the world right now, and I think they're pretty cute. The benefit of these tails is they can make tighter turns. They can recover from external perturbation. So if something bumps them as they're walking, the tail helps them recover. And there's even like a little like RC car with a tail on it that can drive up off of a ramp and do a barrel roll with its tail.

• 18:39Flora Lichtman?

  Well, this is the thing I've been wondering since reading your paper. Should we be attaching tails to more things?

• 18:45Speaker 04

  Yes, why not?

• 18:47Flora Lichtman?

  Would that be helpful? If I had a tail, what would I be able to do that I can't do now?

• 18:54Speaker 04

  Yeah, so as I was walking the dog this morning, I slipped on the ice. And if you had a tail, you'd probably be able to prevent yourself from falling in a really damaging way. You'd probably be able to regain your balance pretty quickly.

• 19:08Flora Lichtman?

  Would I be an Olympic gymnast if I had a tail?

• 19:11Speaker 04

  Yes, I was watching the Olympics and those ladies on the balance beams. I watched them using their arms and legs as inertial appendages, and it was amazing to see.

• 19:23Flora Lichtman?

  Carried tails are so great, why do I not have one?

• 19:27Speaker 04

  It probably has to do with how us humans stand and how we walk and move. This is a huge area of study in bioanthropology and primatologists and understanding why great apes and humans don't have a tail anymore. And I would argue that we do. We have a tiny little tail bone. We have a few tail vertebrae that fuse into our pelvis. And actually, as embryos, we make a tail and it just goes away, probably through apoptosis, so cell death.

• 19:56Speaker 05

  And it retracts a little bit into the body. So making a tail is a part of all of our embryonic programs. We just don't make one outside of our bodies.

• 20:06Speaker 04

  And even though we we don't have an external tail, we still have a lot of those muscles that control the tail. And so I'm learning a lot about those when I go to physical therapy.

• 20:17Speaker 05

  And the pelvic floor, that's where a lot of them are vented up.

• 20:19Flora Lichtman?

  Wait, really?

• 20:21Speaker 04

  Yeah, yeah, absolutely.

• 20:22Flora Lichtman?

  So if I'm doing my pelvic floor exercises, I'm actually activating my tail muscles?

• 20:26Speaker 05

  Yeah, you are.

• 20:27Speaker 04

  I we're doing dissections and we're looking at all of the muscles that control mammal tails. And I'm I'm working those same muscles in in physical therapy.

• 20:36Flora Lichtman?

  A lot of women are going to be interested in this.

• 20:38Speaker 04

  Yes, definitely.

• 20:40Flora Lichtman?

  Talia, can knowing about different tails help you make a super tail for your robot? Like something even better than what you see in nature?

• 20:47Speaker 04

  Yes, so this is exactly what I teach in my bio-inspired robotics course. So if we understand the principles, like the underlying physics principles and the mechanics of how the animals are doing something, and we understand their evolution, we can identify that maybe this animal tail is constrained because maybe of its lineage, it has this certain certain constraint. Maybe it's used for 25 different things, and so it's not going to be the best at anything. But if we understand that underlying principle, we can abstract that and transfer it to an engineering system and make something that's even better than the biological system.

• 21:29Speaker 04

  So in the first lizard paper that we had, we were able to make a tail that was more effective than both a lizard that we were studying in the lab and a simulation of a velociraptor.

• 21:42Flora Lichtman?

  Really?

• 21:42Speaker 04

  Yeah.

• 21:43Flora Lichtman?

  Why do you all care about this?

• 21:45Speaker 04

  Yeah, my my background is biomechanics. I want to know how biology, like biological things, move in the world. And what are the underlying principles of movement that are fundamental and can be applied to all sorts of different species? And so It's really cool to me that many different animals have evolved a tail that is capable of really good inertial maneuvering. And it's not just tails. Like, there are other animals, there's a study showing that bats use their wings as inertial appendages, and praying mantises use their arms and legs as inertial appendages.

• 22:29Speaker 04

  So I'm really excited to learn about the diversity of the morphology of these inertial appendages, and how the morphology affects their effectiveness as that inertial appendage.

• 22:41Flora Lichtman?

  What about for you, Carrie?

• 22:42Speaker 05

  Um, I think tails are such a cool, diverse appendage that have not been given a lot of attention in biology and how they develop and they take shape, especially because they are so diverse. And our, our namesake, we are vertebrates. We are defined by our axial skeleton and our spine. And it is really diverse. Like, you think of giraffes, and humans have the same number of vertebrae in our necks, but giraffe necks are really, really long, and that's just because the vertebrae become much longer. So there's all of this incredible diversity in our vertebral skeleton, and I think the tail is an amazing model to study what sort of ecologies and movements and genetics drive those differences.

• 23:27Speaker 05

  And I just think there's more to the tail than we've been giving it credit.

• 23:30Flora Lichtman?

  Well, thank you. I could nerd out for tails forever, so I appreciate it. Thanks for coming on the show.

• 23:36Speaker 05

  Thanks for having us.

• 23:37Speaker 04

  Thank you so much.

• 23:38Flora Lichtman?

  Dr. Talia Moore, Assistant Professor of Robotics and Mechanical Engineering at the University of Michigan in Ann Arbor, and Dr. Carrie Weber, a postdoc in Kim Cooper's lab in the Department of Cellular and Developmental Biology at UC San Diego.

• 23:57Flora Lichtman?

  And that is about all we have time for. Lots of folks helped make this show happen, including

• 24:02Speaker 04

  Praise Aguchi.

• 24:04Flora Lichtman?

  Sandy Roberts. Robin Kazmer. Jordan Smudjic. I'm Flora Lichtman. Thanks for listening.