Short Stuff: Why do kangaroos hop?

Summary

Stuff You Should Know – "Short Stuff: Why Do Kangaroos Hop?" (May 6, 2026)
Hosts: Josh & Chuck

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Episode Overview

In this breezy "Short Stuff" episode, Josh and Chuck uncover the surprising science behind why kangaroos hop. Mixing their signature banter with fun facts and evolutionary insight, they dive into the unique anatomy, history, and adaptations that have made kangaroos the world's only large hopping mammal. Along the way, they acknowledge their sources, shout out former colleagues, and even veer into the world of classic cartoons and movie recommendations.

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Key Discussion Points & Insights

The Uniqueness of Kangaroos (01:42 – 04:41)

• Marsupials 101:

  • Kangaroos, wallabies, and koalas belong to the marsupial (pouched mammal) family, unlike opossums which also make cameos in the discussion.
  • “They have a marsupial, which is a little pouch where their little joeys develop.” – Chuck (01:44)
  • Baby kangaroos (“joeys”) are essentially born prematurely and crawl into the pouch where further development happens.
    • “The little joey latches onto a nipple in there and the nipple grows three times in size, just like the Grinch's heart.” – Josh (02:10)

• Historical Encounters:

  • Europeans first recorded kangaroos thanks to Dutch merchant Francisco Pelsaert’s 1629 shipwreck.
  • The word “kangaroo” supposedly comes from an Aboriginal term meaning “I don’t know.”
    • “Apparently an aboriginal word for I don't know. Isn't that awesome?” – Josh (04:25)

Evolution of Hopping (04:41 – 07:31)

• Kangaroos are the only large mammals that move by hopping. Their ancestors, 25 million years ago when Australia was a rainforest, weren’t hoppers—they were climbers.
• Evolution adapted their anatomy as Australia's ecosystem shifted from rainforest to grassland, compelling kangaroos to move efficiently over larger distances.

Anatomy of a Hop: Adaptations Explained (07:31 – 13:16)

• Feet and Toes:

  • Kangaroos have two big feet, two small arms (unlike four-legged opossums), and a distinctive setup of toes:
    • First toe: vestigial or missing
    • Second & third toes: fused together (“almost like my sister... she had webbed toes.” – Josh & Chuck, 08:05)
    • Fourth toe: “massive beast of a toe… this is where the actual hopping begins.” – Josh (08:17)
    • Fifth toe: provides added balance

• Elastic Tendons:

  • Powerful elastic tendons in their hind legs act like springs, storing and releasing energy for massive, energy-efficient hops.
    • “When they go downward, all of that tendon gets a bunch of energy... when they bounce upward, it's released and it can send them flying.” – Josh (09:19)

• Performance Stats:

  • Speed: Up to 15–20 mph (24–32 km/h)
  • Distance: 25 feet (7.5+ meters) in a single bound
  • Height: Up to 6 feet (nearly 2 meters)
    • “It could jump right over either of us, Chuck.” – Josh (10:12)

Why Hopping? Efficiency Matters (11:25 – 13:16)

• Tail Counterbalance:

  • Kangaroo tails act as counterweights during hops, moving opposite to their feet for perfect balance.
    • “That tail moves down... when they land, the tail raises. So it kind of just does this little opposite motion to balance everything out.” – Chuck (11:03)

• Bio-Mechanical Efficiency:

  • The kangaroo’s unique physiology means the faster they hop, the less energy they use—making them one of the most efficient land travelers.
    • “The faster they hop, the less energy they have to expend. It's a pretty beautiful system.” – Josh (11:29)

• Respiratory Hack:

  • Kangaroo breathing is tied to their hopping motion: the act of bending and leaping helps contract and expand their respiratory system, pushing air in and out with minimal effort.

• Tail as a Third Limb:

  • At slower speeds (like grazing), kangaroos prop themselves up with their tail, using it almost like a “third foot.”

Kangaroo vs. Wallaby: Size Matters (13:39 – 14:12)

• Wallabies are essentially smaller versions of kangaroos, with shorter legs and heights around 3 feet; kangaroos can reach up to 8 feet tall.
• “Mainly it's—the kangaroo is just a lot bigger... they can be like 8ft tall, whereas a wallaby is maybe like 3ft a little over.” – Chuck (13:41)

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Notable Quotes & Moments

• On Joeys in the Pouch:
  • “The nipple grows three times in size, just like the Grinch's heart.” – Josh (02:12)
• On Shrinking with Age:
  • “I used to be 5'10". Now I'm more like 5'9". I'm shrinking as we all are.” – Chuck (10:30)
  • “Does that mean our vertebra are fusing together or like our knees are getting shorter?” – Josh (10:37)
• On Efficiency:
  • “The faster they hop, the less energy they have to expend.” – Josh (11:29)
  • “One of the most efficient travelers in the animal kingdom overall.” – Chuck (11:58)

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Fun Digressions (14:11 – 15:56)

• Animated Show Recs:
  • Josh and Chuck reminisce about "Rocko's Modern Life" (Rocko is a wallaby!) and mention "Darkwing Duck" and "Bluey."
• Movie Talk:
  • Spontaneous review of Jake Gyllenhaal’s thriller "Enemy" (15:00–15:56), with Josh warning about reading too many online theories: “It was better before I knew, and I just had to accept it on its own terms.”

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Timestamps for Important Segments

• 01:42 – Introduce marsupials and unique kangaroo reproduction
• 04:25 – The origin of the word "kangaroo"
• 07:31 – Anatomy of kangaroo feet and the importance of the fourth toe
• 09:19 – The role of elastic tendons in hopping (spring-like mechanism)
• 09:57 – Kangaroo hopping stats: speed, distance, and height
• 11:03 – How their tail aids balance during hopping
• 11:29 – Why hopping is so efficient for kangaroos
• 12:32 – Kangaroo respiratory efficiency linked to hopping
• 13:39 – Kangaroo vs. wallaby size comparison
• 14:11 – Cartoons and movie recommendations
• 15:56 – Wrap-up

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Closing Thoughts

Josh and Chuck's exploration of kangaroo locomotion blends solid evolutionary biology with their trademark wit, diving deep into why these incredible marsupials are nature's champion hoppers. Whether pondering the origin of "kangaroo," analyzing toe anatomy, or marveling at their energy economy, the hosts deliver a punchy, accessible lesson in animal adaptation—sprinkled with pop culture asides and personal anecdotes.

"The faster they hop, the less energy they have to expend. It's a pretty beautiful system." – Josh (11:29)

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Recommended if you:

• Like biology, Aussie wildlife, or just want quick, fun animal facts with a side of Josh & Chuck’s banter.
• Want to understand one of nature's coolest feats of engineering, all in under 20 minutes!

Transcript

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[Josh]

I'll wait.

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[Josh]

They're right by you. Hey, and welcome to the Short Stuff. I'm Josh and there's Chuck and Jerry's here for Dave. And we're just hopping along talking about kangaroos and how they hop.

[Chuck]

That's right. Want to thank our old colleague Kristen Conger for writing this article from How Stuff Works back in the day.

[Josh]

And creator of Unladylike the podcast too,

[Chuck]

as well as Jennifer Horton wrote another article that I used.

[Josh]

Great too Remember Jennifer?

[Chuck]

And then I think the San Diego Zoo website and Nat Geo all pitched in for this one.

[Josh]

I thought this was a particularly well researched short stuff, so I should have known that Jennifer Horton and Kristen Conger had something to do with it.

[Chuck]

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 ruse are marsupials or pouched mammals because they have a marsupial, which is a little pouch where their little joeys develop.

[Josh]

Yeah, we talked, I think a lot about this in the naked mole rat episode where essentially like the, 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 of 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.

[Chuck]

Yeah. That's maybe the fact of the podcast for me, that's kind of nutty.

[Josh]

Oh, I'm sorry. I took that. I didn't realize that it was.

[Chuck]

I have to always take the fact of the show.

[Josh]

I like to, you know, I mean,

[Chuck]

I know it's in my contract and not yours, but I'm willing to give every now and then.

[Josh]

That's very generous of you. Thank you.

[Chuck]

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 little, littler arms.

[Josh]

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 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 titanica arms are just kind of hanging out there, not doing much of anything.

[Chuck]

Yeah. Except boxing, probably. The kangaroo. The first sightings apparently trace back to a Dutch merchant named Francisco Pelsaert, 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.

[Josh]

Here's the fact of the podcast for me, Chuck. Okay, can I take this one, too, or should I tee you up?

[Chuck]

No. Double up, baby.

[Josh]

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.

[Chuck]

That's pretty funny.

[Josh]

It is.

[Chuck]

Here's the deal, though, is kangaroos are the only large mammals to hop. And that's basically as. 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.

[Josh]

Yeah. So they. They actually developed what ends up helping them hop long before they actually started to hop. We call that the fourth toe. If you look at a kangaroo's foot, you can see how it's. How it's hopping. And, Chuck, I think I've kind of set us up for a ab break, and we're going to come back and finally talk about how kangaroos hop. What do you think?

[Chuck]

All right, let's do it.

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Within probably 10 days, I'd put on £10. I was having trouble stopping the muscle growth.

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[Josh]

Okay, where I left off, Chuck, I was talking about the fourth toe. And this is the. 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. Then when you. You get. Oh, yeah, I didn't know she had webbed toes. Cool. Is she a fast swimmer?

[Chuck]

No, that's what everyone always asks. It's just the second third toe on one foot have always been stuck together.

[Josh]

But surely it would have to give you an advantage to some degree.

[Chuck]

I don't know. I can't remember the last time I swam with her.

[Josh]

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. With the leg bones of the kangaroo's legs. And this is where the actual hopping begins.

[Chuck]

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 and learned it eventually. They do have a fifth, though, we should mention, that provides a little bit of support. But if you look up, like the foot of the hind leg from behind, they have these really. I mean, you can't see because it's on the inside, but they have these really strong elastic tendons that store energy up for those massive, massive jumps.

[Josh]

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's released and it can send them flying. Chuck. I had no idea how far they can hop and how fast. Did you?

[Chuck]

Yeah, but it's always fun to relearn that, you know? Cause it's pretty astounding.

[Josh]

Okay, so they can go up to 15-20 mph. And for those of you in Australia who don't know, no, that's about 24 to 32 kilometers per hour. That's fast. That's like golf cart speeds at top speeds even.

[Chuck]

That's faster than a golf cart. Yeah.

[Josh]

And then it can propel itself about 25ft forward, almost seven or more than seven and a half meters. And six feet high. Yeah, nearly two meters high. And so it could jump right over either of us, Chuck.

[Chuck]

Yeah, absolutely. I mean, you're taller than I am, so you might get your forehead grazed.

[Josh]

It could just barely clear me. I'm five foot eleven and a half, if I'm fully honest.

[Chuck]

Yeah. They would look at me and just be like, no problem, shorty.

[Josh]

They just free willy right over you.

[Chuck]

I used to be 5 10. Now I'm more like 5 9. I'm shrinking as we all are.

[Josh]

Yeah. What is up with that?

[Chuck]

You shrink, you know.

[Josh]

But I mean, does that mean our vertebra are fusing together or like our knees are getting shorter? Have we compacted the shin bones and our legs and that's what's doing it? It doesn't make any sense to me.

[Chuck]

Well, we should do an episode like a shorty maybe on the shrinking as you age, because it'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.

[Josh]

Oh, I didn't know that.

[Chuck]

Yeah.

[Josh]

Wow. What a development.

[Chuck]

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.

[Josh]

And it makes a really satisfying, boring sound.

[Chuck]

Of course.

[Josh]

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.

[Chuck]

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 by using your own energy.

[Josh]

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 sprawing, I think, is the technical term, even further. So when they get going, they really can just. They can just keep going a while. They're 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.

[Chuck]

Yeah. Yeah. Why does it say fifth in here? That's so weird.

[Josh]

I know. Because they specifically said that they're two front arms, you know.

[Chuck]

Hey, well, maybe I'll get in touch with Connor. It gives me a good reason to get in touch with her. Say, what the hell did you mean this fifth leg thing all those years ago?

[Josh]

You're gonna ruin her week.

[Chuck]

She's like, who is this?

[Josh]

Right.

[Chuck]

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 it's. 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 8ft tall, whereas a wallaby is maybe like 3ft a little over.

[Josh]

Can you really say it any other way than that?

[Chuck]

I don't think so.

[Josh]

I mean, why would you. Anyway, yeah, this is probably long after your wheelhouse, but did you ever watch Rocko's Modern life cartoon?

[Chuck]

Heard of it.

[Josh]

It's a great cartoon. Yeah, it's a cute little cartoon. It was on Nickelodeon, and Rocko was at wallaby.

[Chuck]

Oh, nice.

[Josh]

Did you ever watch Darkwing Duck?

[Chuck]

Never heard of it.

[Josh]

No, that's not it.

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[Josh]

With Jason Alexander as the duck.

[Chuck]

Oh, I don't think I know of such a show.

[Josh]

It was like a raunchy superhero duck show. That was pretty good, whatever the name of it was. Look it up. Jason Alexander. George Van Seinfeld played the main duck.

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Oh, wow.

[Chuck]

That was a good one, too.

[Josh]

Yeah. I think Darkwing Duck is like a DuckTales spinoff. That's not what I'm talking about.

[Chuck]

All right, well, I mean, if we're recommending animated shows, I might as well. And we're in Australia. I gotta recommend Bluey again. Still watch that?

[Josh]

Okay, I never watched that one.

[Chuck]

Yeah.

[Josh]

So stepping out of the animated shows, but continuing with the recommendations. Oh, boy, here we go. I watched the Jake Gyllenhaal movie Enemy last night.

[Chuck]

Oh, yeah.

[Josh]

It was Denis Villeneuve. Have you seen it?

[Chuck]

I saw it back then.

[Josh]

Man, it is a good movie.

[Chuck]

Yeah. Crazy ending.

[Josh]

Yes. So it was one of those movies that I was just sitting there thinking about it afterward. And so I love those, because if you go look them up online, there are people who have 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 to accept it on its own terms.

[Chuck]

Yeah. Love that movie.

[Josh]

All right, well, that's it for Enemy. And that's it for, obviously, Kangaroo hopping, right?

[Chuck]

That's right.

[Josh]

Short Stuff is

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