Stuff You Should Know - Short Stuff: Why do kangaroos hop?

Episode Date: May 6, 2026

Kangaroos are the only marsupial to hop, which is pretty weird. We'll investigate why. See omnystudio.com/listener for privacy information.

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And creator of unlady like the podcast, too. As well as Jennifer Horton wrote another article that I used. Great too. Remember Jennifer? And then I think the San Diego Zoo website and Nat Geo all pitched in for this one. I thought this was a particularly well-researched short stuff. So I should have known that Jennifer Horton and Kristen Conger has. something to do with it. Yeah. So we're talking about kangaroos a little bit, mainly going to get to how and why they hop, but we should start out by talking about the fact that roos are marsupials or

pouched mammals because they have a marsupium, which is a little pouch where their little joys develop. Yeah, we talked to think a lot about this in the Naked Mulrad episode, where essentially like the marsupial fetus does not develop as long inside. the body of the mom as it does inside the pouch. Essentially, at some point, it's what you would call born, but really it's just crawling out of the birth canal, outside into the world for a second, and into the pouch, and then the little Joey latches onto a nipple in there, and the nipple grows three times in size, just like the Grinch's heart. And so the little Joey couldn't let go the nipple, even if he or she wanted to, until they develop a little further.

It's quite ingenious. Hats off natural selection. That's a great one. Yeah, that's maybe the fact of the podcast for me. That's kind of nutty. Oh, I'm sorry I took that. I didn't realize that it wasn't. What do I have to always take the fact of the show?

I like to, you know. I mean, I know it's in my contract and not yours, but I'm willing to give every now and then. That's very generous. I mean, thank you. All right. So Australia is obviously what people, you know, what comes to mind when you think of marsupials in general because koalas and kangaroos. but we have done a great episode on the opossum, which live all over the place, especially north-central and South America.

But we're talking about kangaroos and wallabies here because they don't have four legs like our opossum friends. They have two big old feet and two littler arms. Yeah, that's a great way to think about it. They don't have four legs. They have two legs and two arms. And it makes sense. Like if you've ever seen a kangaroo or you just bring up.

bring one to mind if you're capable of using your mind's eye, they're sitting on their feet and they're standing or sitting upright and their little almost Titanic arms are just kind of hanging out there, not doing much of anything. Yeah, except boxing probably. The kangaroo, the first sightings apparently traced back to a Dutch merchant named Francisco Pelsert who got shipwrecked off the coast of Australia in 1629, And about 150 years later, they were pretty well known throughout Europe.

And by 1791, they had brought those things over to London, England. Here's the fact of the podcast for me, Chuck. Okay. Can I take this one too or should I tee you up? No, double up, baby. So the name kangaroo, the word, as far as anyone is able to say, we don't know for sure, it's apparently an Aboriginal word for, I don't know. Isn't that awesome?

I don't know. That's pretty funny. It is. Here's the deal, though, is kangaroos are the only large mammals to hop. And that's basically, like, they're, you know, bunnies will hop a little bit, but the kangaroo moves around primarily by hopping. And I guess you wouldn't consider a bunny a large mammal anyway. Here's the deal. If you go back to 25 million years ago and look at the fossil record, they didn't hop because Australia was a rainforest at the time.

So those kangaroos were climbing around for a long, long time. Yeah. So they actually developed what ends up helping them hop long before they actually started to hop. We called it the fourth toe. If you look at a kangaroo's foot, you can see how it's hopping. And Chuck, I think I've kind of set us up for an ab break. And we're going to come back and finally talk about how kangaroo's hop. What do you think? All right, let's do it. John, Josh, Josh, Josh. Listen, and you're there. For heart-wrenching knockouts.

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there's a seat for you right here. Listen to everyone. Watchers Women's Sports from the IHeartRadio app, Apple Podcast, or wherever you get your podcast. Okay, where I left off, Chuck, I was talking about the fourth toe, and this is the design element that allows the kangaroo to hop, because if you look at a kangaroo's foot, the first toe, looking at the kangaroo's foot from the inside of the foot outward, the first toe is pretty puny, might not even be there. The second and third toes, they're okay. They're like smallish, and they each have a nail, but they seem to be fused together.

So like web toes almost. Like my sister. And then when you get, oh yeah, I didn't know she had web toes. Yeah. Is she a fast swimmer? No, that's what everyone I always asked. It's just the second third toe on one footer had always been stuck together. But surely it would have to give you an advantage to some degree.

I don't know. I can't remember the last time I swam with her. Well, next time you get a chance to race her and let me know how it turns out. All right. Finally, we get to the fourth toe, and the fourth toe is like just this massive beast of a toe, and it's in line with the leg bones of the kangaroo's legs, and this is where the actual hopping begins. Yeah, that's an actual adaptation, and like you said, that preceded their ability to hop, so I'm not even sure what the deal is with why they adapted that to begin with. But, I mean, maybe it's just because they went from rainforest to sort of dry grassy plains and they needed to get around more.

I don't know. Learned it eventually. They do have a fit, though, we should mention. That provides a little bit of support. But if you look up like the foot of the hind leg, like, you know, from behind, they have these really – I mean, you can't see it because it's on the inside, but they have these really strong elastic tendons that store energy up for those massive, massive jumps. Yeah, like a spring. When they go downward, all of that tendon gets a bunch of energy, kinetic energy stored in it. And then when they bounce upward, it gets, it's released. And it can send them flying, Chuck. I had no idea how far they can hop and how fast, did you? Yeah, but it's always fun to relearn that, you know, because it's pretty astounding. Okay, so they can go up to 15 to 20 miles per hour.

Yeah. And for those of you in Australia who don't know, that's about 24 to 32 kilometers per hour. That's fast. That's like golf cart speeds, at top speeds even. That's faster than a golf cart, yeah. And then it can propel itself about 25 feet forward, almost more than 7 and a half meters, and 6 feet high. Yeah. Nearly two meters high.

And so it could jump right over either of us. Chuck. Yeah, absolutely. I mean, you're taller than I am, so you might get your forehead grazed. It could just barely clear me. I'm 5'11 and a half, if I'm fully honest. Yeah, they would look at me and just be like, no problem, shorty. They just free willy right over you. I used to be 510. Now I'm more like 5.9. I'm shrinking, as we all do. Yeah, what is up with that? You shrink, you know.

But I mean, does that mean our vertebra are fusing together or like our knees are They're getting shorter. Have we compacted the shin bones in our legs and that's what's doing it? It doesn't make any sense to me. Well, we should do an episode, like a shorty maybe on the shrinking as you age because that's definitely a thing. That's why, like you see an old man that has these giant ears. They didn't always look that way.

Oh, I didn't know that. Yeah. Wow, what a development. All right. So back to the kangaroo. We need to talk about their tails a little bit because they have those huge tails that act as a counterbalance to the hind feet. So if you look at a kangaroo hop, that tail moves down.

Like in midair, that tail is moving down to meet kind of where the feet are. And when they land, the tail raises. So it kind of just does this little opposite motion to balance everything out. And it makes a really satisfying boring sound. Oh, of course. So what's great about this? You said that the kangaroo is the only land animal that or an only large mammal that hops. And the reason why it hops is because,

it's actually a tremendous adaptation for moving quickly across land in a really efficient manner. Because the way that the kangaroo is built, the faster they hop, the less energy they have to expend. It's a pretty beautiful system. Yeah, it's pretty crazy. And one of the most efficient travelers in the animal kingdom overall, you know, that, like you said, they had that great range. and part of what's going on with their efficiency is they have a like when they're bending down to jump and then leaping up that's contracting and suppressing their respiratory system which actually is like makes it more efficient it makes those stomach muscles contract and expand and just forces air in and out without like having to do so you know by using your own energy yeah and they also have to use less muscle energy in their legs because when they jump really far high and fast, when they land, those super elastic tendons that help them hop just contract even further. And that means that they expand or sproying, I think, is the technical term, even further.

So when they get going, they really can just keep going a while. Also, their heart is really attuned to this kind of endurance workout, right? Yeah. It's when they're not going fast, when they're just kind of hopping from place to place and grazing. that's when it's harder. And they have to end up using their tail to kind of balance themselves as basically like a, well, a third foot. Yeah. Yeah.

Why does it say fifth in here? That's so weird. I know because they specifically said that they're two front arms, you know? Hey, well, maybe I'll get in touch with Konger. It gives me a good reason to get in touch with her. Say, what the hell did you mean with this fifth leg thing all those years ago? You're going to ruin her week. She's like, who is this?

Right. I guess we'll close quickly just on a little, you know, I mentioned the wallaby. The slight differences between the wallaby and the roo. Mainly, the kangaroo is just a lot bigger. They have a lot more length between their ankles and their knees, and they're just taller. They can be like eight feet tall, whereas a wallaby is maybe like three feet, a little over. Can you really say it any other way than that? I don't think so.

I mean, why would you anyway? Yeah. This is probably long after your wheelhouse. But did you ever watch Rocco's Modern Life? Never heard of it. It's a great cartoon. Yeah, it's a cute little cartoon. It was on Nickelodeon.

And Rocco was a wallaby. Oh, nice. Did you ever watch Darkwing Duck? Never heard of it. No, that's not it. What was The Duck with Jason Alexander as The Duck? Oh, I don't think I know of such a show. It was like a raunchy, like,

superhero duck show. That was pretty good. Whatever the name of it was, look it up. Jason Alexander, George from Seinfeld, played the main duck. Oh, wow. And that was a good one, too? Yeah, I think Darkwing Duck is like a Duck Tales spinoff. That's not what I'm talking about.

All right. Well, I mean, if we're recommending animated shows, I might as well. And we're in Australia, I got to recommend Bluey again. Still watch that. Okay. I never watched that one. Yeah. So stepping out of the animated shows, but continuing with

the recommendation. Oh, boy, here we go. I watched the Jake Jillenhall movie Enemy last night. Oh, yeah. It was Denisville. Uh-huh. Have you seen it? I saw it back then. Man, it is a good movie. Yeah, crazy ending. Yes. But so like it was one of those movies that I was like just sitting there thinking about it afterward. Yeah, yeah. And so I love those because if you go look them up online, there are people who have like given great thought to explaining these things. And I found, I think on Slash film, a really great explanation of what was going on. But be forewarned, if you watch Enemy, you may regret reading the explanation of it. It's almost, to me, it was better before I knew. And I just had had to accept it on its own terms.

Yeah, love that movie. All right. Well, that's it for Enemy. And that's it for obviously kangaroo hopping, right? That's right. Short stuff is that? Stuff You Should Know is a production of IHeartRadio. For more podcasts to My Heart Radio, visit the Iheart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.