SciShow Tangents - Giant Rodents

Episode Date: March 12, 2019

When can you start calling a rodent “giant?” When it’s twice the average size of its species? When you’re not grossed out by it? When it could be a mascot for a family fun center? We don’t really have a precise answer to that… but this week, we’re exploring the science of big ol’ rodents! Turns out, giant rodents have shaped the environment in lots of ways, from ancient megafauna stomping through South American wetlands to beavers affecting the climate. And even though they sound kind of scary, giant rats might be able to save human lives. But the real question is: what’s up with capybara anal pouches?Sources:[Truth or Fail]https://news.northwestern.edu/stories/2015/02/making-teeth-tough-beavers-show-way-to-improve-our-enamel-http://www.sci-news.com/biology/science-biswamoyopterus-laoensis-new-species-flying-squirrel-laos-01361.htmlhttps://www.apopo.info/en/tuberculosis-detection/projectshttp://www.treatmentactiongroup.org/tb/backgroundhttps://www.theguardian.com/science/2016/feb/23/rats-who-sniff-out-tubersulosishttps://news.nationalgeographic.com/news/2014/08/140816-rats-tuberculosis-smell-disease-health-animals-world/[Fact Off]Hippos & biggest rodent:Beavers & carbon emissions:https://www.eurekalert.org/pub_releases/2018-08/uoh-bha082918.phphttps://www.sciencemag.org/news/2013/07/what-role-do-beavers-play-climate-changehttps://link.springer.com/article/10.1007%2Fs13280-014-0575-y[Ask the Science Couch]Gigantism:https://www.smithsonianmag.com/science-nature/why-king-kong-should-have-been-blue-whale-180962603/https://www.nature.com/articles/482008dhttps://news.nationalgeographic.com/news/2012/05/120521-killer-mice-birds-gough-island-endangered-animals-science/https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-1795.2012.00534.xhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC4358651/[Butt One More Thing]Capybara anal pouches:https://zslpublications.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7998.1984.tb05087.x

Hello and welcome to SciShow Tangents, the lightly competitive knowledge showcase starring some of the geniuses that make the YouTube series SciShow happen. This week, joining me, as always, are Stephan Ginn. Hey. How you doing, buddy? I'm doing all right. Good. What's your tagline?

Never go in against a Sicilian when death is on the line. And we're also joined by Samuel Schultz. Hello. Isn't it Samuel? Uh-huh. Officially on the birth certificate? Yeah. You thought about it for a second.

Well, my brother is just Will and not William or anything like that. So it does get a little, I wonder why my parents did that to me. You haven't asked them. I have. They didn't have an answer. What's your tagline?

A little boy from outer space. We also got Sari Riley up in the house. Sari, what's your tagline? I need a toaster. And I'm Hank Green. I am doing well. And my tagline is honey bunches of oats. So if you don't know about SciShow Tangents, it's a time when we get together, the four of us.

We try to amaze each other. We try to one-up each other with better and better science facts for each other's delight. We're playing for glory, but we're also keeping score in the form of Hank Bucks. And at the end, there will be a winner, and that winner will get nothing. We do everything we can to stay on topic here at SciShow Tangents, but it is called SciShow Tangents. So if we go on a tangent, the rest of the crew gets to decide whether the tangent was worthwhile. And if it wasn't, then you have to give up a Hank Buck. Now, as always, we're going to introduce this week's topic with a traditional science poem from Sam.

From Mickey Mouse to Chuck E. Cheese, humans seem to love a man-sized cartoon mouse or rat wearing shoes and gloves. But in the distant mists of time, there have really been super giant rodents that weighed more than 15 men. With foot-long teeth and deadly jaws, they probably wouldn't be the greatest mascots for a park or a pizza place MC. And you wouldn't even need to travel to a distant era to find a four-foot flying squirrel or a dog-sized capybara. Smaller and cuter though they are, they still aren't fit for showbiz because they'd rather poop and chew than entertain your kids. You did it. I did it. It was great.

Hank Buck for Sam. Thank you. I loved it. It was great. Hank Buck for Sam. Thank you. I loved it. And I think we may hear about some of these giant rodents in today's SciShow Tangents episode on giant rodents, which you probably already knew because of the title of the episode.

Yeah, that's a little bit of a flaw in the system. I guess we turn to Sari to tell us what a giant rodent is. This is one of the hardest definitions because it's so nebulous. Right, of rodent and giant? Rodent, not so much. Rodent, we know. It's an order in mammals called rodentia. And I think the thing that sets them apart the most is the way that their teeth grow and the way that they're positioned in their jaw. So they have incisors in the front that continuously grow their entire lives. And the only way they get worn down is by biting and chewing, which is why it's so important for all rodents to have stuff to gnaw on. And

that's like your mice, your rats, guinea pigs, chinchillas, but also bigger ones like beavers and porcupines and capybaras. Wait, are squirrels one of them? I think squirrels are rodents. I hope so. It was in my poem. I think so. Rabbits are not. Right, because they're the lagomorphs. What's the difference there? Their teeth don't grow like that? Rabbit teeth do grow continuously throughout their whole life, but their jaw structure is somehow different.

Hanging out somewhere nearby. Yeah. Where does it get giant? I feel like a beaver is a giant rodent. Like if somebody came on this show, we're talking about giant rodents, and you talk about a beaver, I'd be right here with you. Yeah, that's where my head was in this one. So the three biggest kinds of rodents are beavers, porcupines, capybaras. And those get into, I think, 30 plus pounds starting with beavers.

And so those seem big. And then there are big versions of mice and rats that, to biologists, are giant. Where they're like like compared to a normal mouse this one's giant yeah you see it and you're like that is a small animal yeah i read about a giant one that was twice as big as a normal mouse which is so tiny to me giant rodent seems weird i guess because the word rodent right is like a gross word kind of it's like for a gross little scurrying thing so then when you see like a beaver you're not like oh a rodent right like a gross word kind of. It's like for a gross little scurrying thing. So then when you see like a beaver, you're not like, ooh, a rodent. So maybe that's what the line is once they're not gross

anymore. Yeah, you see a copy bar on you. You're like, that's just a cute animal. Yeah, I'm going to give it a little pat on the head. So I guess we've got like roughly giant is when we're like, oh, that's a rodent? That's awful big. It's not a very scientific topic. And then like the prehistoric ones.

Then that's actually giant. Which we can't talk about too much before my fact off. Oh, okay. But before we get to that, it's time for everybody's favorite time. Where Sari has prepared three science facts for our education and enjoyment. But only one of those facts is true. The other panelists have to figure it out, either by deduction or wild guess. And if we get it right, we get a Hank Buck.

If we don't, then Sari does. Sari, what are your three facts? Hundreds of years ago, the Laotian giant flying squirrel was a messenger animal in Southeast Asia for military, medical, and domestic deliveries. was a messenger animal in Southeast Asia for military, medical, and domestic deliveries. They have a lot of endurance and seem to use smell and the Earth's magnetic field to navigate over long distances in the brush, similar to homing pigeons. I want that one. Fact number two. African giant pouched rats are rodents but aren't technically rats.

They have a keen sense of smell and are trained to identify tuberculosis and spit and mucus samples. Microscope tests that look for bacteria aren't always accurate, so these rodents have saved lives. Or fact number three. In the 1940s, U.S. military researchers worked on Project Timber. They were studying beavers' extremely strong teeth and wanted to train them to gnaw down wooden building supports instead of trees. Super sneaky. But the project was canceled because it wasn't destructive enough. I don't believe that anyone has ever called a beaver not destructive enough. All right.

So I got to go straight to African giant pouch rats, which you said they weren't rats. Do they have a giant pouch? I think that refers to their cheek pouches. Oh, okay. All right, all right, all right. But they are rodents. They are rodents, yeah. Okay, so your three facts are potentially useful rodents. Yeah, three potentially useful rodents.

It could be. A flying squirrel messenger, a sniffing rat, disease sniffing rat, or beaver weapons. Weaponized beavers. So one thing I know about America is we've tried to weaponize everything. So if we haven't weaponized beavers, I would be surprised, honestly. So I might—leaning strongly toward that. But we've met a beaver, and they seem very slow and lazy. I wouldn't look at a beaver

and think, that thing could chew through her supports quickly. Wouldn't that be what they would need to do? They don't necessarily have to chew through supports quickly. Like, they could just come back.

But they can chew it on a tree, no problem. They do it all the time. Just throw a bunch of beavers in the basement of the building. Hmm. Okay. I feel like for a lot of reasons

that wouldn't work because they're like a family unit. They seem very temperamental. I guess it didn't work, so there we go. It's true. I do agree that you can't throw a beaver someplace and be like, chew! They tend to want to settle down first before they get to the really active chewing.

So I'm still feeling strong on Project Timber because I figure we've tried. Yeah, okay. At the very least, we've tried. Giant flying squirrel, obviously I want it to be true. I know that. At the very least, we've tried. Giant flying squirrel, obviously, I want it to be true. I know that they're real. They were in your poem. They were in my poem,

but all I read about them was that they are real. Yeah, yeah. I don't know anything else about them. I don't know if they were used for anything. Yeah. And they're currently living, these four-metered flying squirrels. That's the thing. They have only found 10 of them,

according to my research, and they were all dead. They pop up in meat markets sometimes. Oh, I see, I see, I see. This was hundreds of years ago. Yeah. All right. As part of that.

Okay. Oh, damn. Then I guess I don't know. I'm leaning towards the middle one. Giant pouch rat can smell TB. Was it TB and cancer or just TB? Just tuberculosis. Oh, boy. Maybe not then. I don't know. What do you mean? I feel like you could smell tuberculosis.

You think so? Yeah. Sure. It's an infection in your respiratory system which means it would come out in your breath I feel like it's easier to smell TB than cancer I'm gonna go with that one I'm gonna go with okay I have to stress that we cannot all pick the same answer I agree

with you because and it doesn't matter because I'm going for project timber weaponized beavers okay I definitely read about tuberculosis smelling rats but I don't know if it was this species of rats, but I'm going to go with number two. I think that Sari wouldn't. I think Sari would not do it with just a different species. I am also betting on that.

What if it's a different disease, though? Because I feel like I've heard of cancer smelling rats. We're going to find out right now. Number two is correct. I wanted weaponized beavers. I didn't get them. So are there seeds of truth in weaponized beavers that can be some kind of salve to my ego? Nope.

They do have extremely strong teeth, and I thought that was cool. They have iron molecules as part of it, so they're kind of orangey and just like got really strong enamel. And so I just wanted to see if I could make up a fake military project convincingly. So I tried. You did. And the flying squirrel thing, I just also found that it existed and then made up everything else. They're like four feet tall. Yeah, they're huge.

But there's only, we don't know if there's any alive? I think there are. They're just not, they're not easy to find. I don't think they've ever- I feel like a giant squirrel would be easy to find. Maybe nobody's really put a lot of time into it. I think it's very easy to find the little ones. That's true.

And then we've also got actual TB sniffing rats. And they're very cute and very good. They're called hero rats. So an organization has discovered that these African giant pouched rats can be trained over the course of nine months to sniff various things. And so they've trained some of them to sniff for landmines beneath the surface of the ground. They wear little harnesses and walk around and sniff for explosives. And then they find it and then tell people about it? Yeah.

So they have a handler, I think. They're not heavy enough to blow up, right? Yeah, they're not heavy enough so they can walk over the ground, which is why it's way safer to train them instead of having humans walk around and find them. But they have also been used to sniff for tuberculosis, which is a very serious disease, especially in some African nations, like where these good rats are, where these good rats are. Yeah. And in a lot of these countries, tuberculosis is a really high cause of death, but they don't have the technology needed to

screen for it really easily. Like in our hospitals, we have, I don't know, machines that can analyze molecules very easily. But the main test that a lot of these hospitals are using is a microscope test where they take a sample of sputum, which I think is a very weird word. It's a very bad word. It's like the spit and mucus that tuberculosis patients hack up. And so they look at it under the microscope and are looking for bacteria in it, any sign of it. And the problem is, is especially if someone is HIV positive with a immune system that's compromised, not very many bacteria can make them extremely sick. And so it's really hard to find the bacteria in these microscope tests. But rats can be trained to sniff it out and do it faster, more efficiently, and go through a bunch more samples than humans with pretty high accuracy.

Wow. So you're intentionally putting rats in healthcare centers. Yeah. That's usually the opposite of how it works. They're using rats to actually diagnose people. And they just stick a rat in a container and then give them a bunch of samples to sniff. And usually, from what I read, they like scratch the ground, which seems kind of cute if they smell disease. And then the researchers just like check a bunch of boxes.

And usually that's not like a confirmed diagnosis. It just tells the doctors that they should go back and check that sample again manually. But they've increased diagnoses by a lot. In the first 16 months that they did this program of rat sniffing samples from patients, they tested about 12,500 patients. 1,700 had been found positive already at health clinics using the microscopes. But then the rats detected another 764 patients on top of that that were confirmed to have tuberculosis. So they're like genuinely saving people. That's great.

And you're not being weaponized at all. You're being opposite of that. How big are they, though? They get up to about a meter long. Oh, that's big. Does that include a tail? Yes, including the tail. Okay.

I'm more on board now. Yeah. All right. Well, it's time for us to talk about even giant rats, or I guess rodents, and we're going to do that right after we hear about some advertising. Welcome back. Here's our totals in terms of our Hank Buck scores. Sarah, you got one. Hank, that's me.

You got zero. Sam, coming in first with two. And Stefan has one. I forgot about the poem, Hank Buck. I thought we were all tied. No, you're all losing, except for Sam. But it's my chance to come back. And Stefan, you too.

You could claw your way back. You could win, even. Because it's time for the Fact Talk, where two panelists have brought in science facts to present to the others in an attempt to blow your minds. Stefan and I have brought in facts this week. Sari and Sam have the opportunity

to award the Hank book to the fact they like the most. And the person who goes first is the person who is sneakiest. Like, rodents are sneaky. Masters of stealth.

You know, know that they're there. Are they sneaky? They are. I once had a mouse on my face. Oh, I think you've talked about this

on the podcast. Yeah, I woke up, I was in the forest and I woke up with a mouse on my face and I grabbed it've talked about this on the podcast. Yeah, I woke up. I was in the forest and I woke up with a mouse on my face and I grabbed it and I threw it. Was the mascot costume that you wore a rodent? No, I was Willie the Wildcat. Oh, okay. I was a beaver,

so I was technically a rodent. Sari not only has hung out with rodents, she's been one. Tim the beaver. For like your high school? We have to leave it up for college. To you guys. Oh, We have to leave it up for college. To you guys. Oh, wow. You're our mascot in college.

That was very judgmental. That's what I put those days behind me in high school. Tell me, you guys have to tell us which you think is, who is sneakier. There's three people

in the room, so you guys all have to vote. Who's sneakier, Stefan or Hank? Oh, no. This is a trick. Who's sneakier, Stefan or Hank? Oh, no. This is a trick. Who's sneakier? Do I get to vote?

No. No. Stefan would try to be sneakier to avoid people. Uh-huh. Uh-huh. Maybe he has more experience because he likes people less than I do. Yes. I feel like head down, we'll just go.

Yeah. But maybe Hank has more like actual tested methods for escaping and sneaking past people than Stefan does. It's true. Sometimes I have to sneak past people. I bet Hank is sneakier. It's okay. Sam thinks I'm sneakier. I will buy that logic. I feel like Hank is more professionally sneaky than Stefan is.

Stefan is a casual sneaker. An amateur sneak. Hank is a professional sneak. I cannot believe this. That you think you wanted to be sneaky? I can't. I'm just being described as a casual sneak, an amateur. I don't like this at all.

All right. Well, I get to go first anyway. This was a long process. So here is my fact. As I believe we may have discussed on Tangents briefly before, Pablo Escobar, the drug lord, had hippos. And I have written down here, weird flex, but okay. And since then, the hippos have moved beyond their original lake enclosure where they were, and they have gone into wild ecosystems.

There is a debate raging right now about whether these hippos might actually be good for the environment as an invasive species because they're filling a niche once occupied by now extinct megafauna. For example, the world's largest ever known rodent, Josephophortegassia monosci. Nailed it. Which probably weighed upwards of 2,000 pounds and looked very similar to guinea pigs, but 2,000 pounds though. Hippos clock in at around 3,000 to 4,000 pounds. So when people say that capybaras are giant guinea pigs, these things make that sound silly

because they are 10 times bigger than a capybara. So some ways that hippos may help increase biodiversity and thus these megafauna rodents may have once done, consuming overgrowths of aquatic grasses, reforming the landscape with their giant bodies and creating channels through mats of grass, and creating more variable levels of nutrients and oxygen in a single river system. So Josephophagos, I've got to give these things a better name, went extinct around 4 million years ago,

likely because of new species invading after North and South America first became connected. But these new hippos, they got no predator that can stand up to them except maybe people. So we will see how this turns out. Oh, wait a minute. Yeah.

Pablo Escobar had hippos. Yes. And then they just let them go? They got out. Uh-oh. They're real big. I don't actually get the impression that they were enclosed. Ah.

They like put, and I don't, I did not figure this out how they got out, but I think that they just like built a man-made lake and they were like, put the hippos there. They won't be able to go very far because there's no nearby stuff for them to go to, but then they figured it out. Oh. But maybe there were like some kind of enclosures, but they're out now. Did they have children? Oh, yeah.

They're officially an invasive species. They probably could kill them if they wanted to. And they're looking into how to sterilize them because people nearby don't like the idea of the hippos getting killed because they like the hippos. These must be some friendly hippos.

I don't think they are. I think that they have like some kind of attachment to them that probably once people start dying of hippo, maybe they will lose. And this wasn't the only megafauna that may have been in a similar niche to a hippo in South America. Most of them went extinct when humans arrived. to a hippo in South America. Most of them went extinct when humans arrived. But there was an earlier extinction of megafauna in South America when big cats arrived from North America. Can you expand on the idea of reforming the landscape with their giant bodies?

Yeah. That seems weird and cool. Yeah. So they actually can change how rivers flow by like when they walk around, they like kill grasses. They break apart grass mats. They like the more that they move through an area, they create channels that water can flow through.

And so they become what I think in ecosystem ecology is called ecosystem engineers, like the way that beavers are. And when you take them away, the ecosystem actually, like, the functional, like, what this ecosystem looks like changes because of not having something so significant, you know, moving through it. Was killing all the megafauna, like, a huge mistake on humanity's part? They stopped existing before humans got to South America, so we didn't get the chance. Oh, okay. We didn't do that to the big mouses. Okay.

This was a while back. This is all based on one skull. Yeah, and I read a little bit about these from my poem. They're the ones with the foot-long teeth. They have very big teeth. And they have a bite that's like three times stronger than a tiger. Yep. So they were just like chomping trees, I think, or something.

It seems like they probably chomped grasses in rivers because their molars were actually really small, which indicates they probably didn't chomp on things that were hard. Why they have such a strong bite then? Maybe for like biting predators. That's my jam. So I guess this comes down to Stefan. Do you have a better fact than me? I don't know.

But funny that you should mention ecosystem engineers. My fact is about beavers, but not related to their size. Just about how their activities might be affecting their environment because they have pretty big effects on their ecosystems. As most people probably know, beavers make dams. And I thought they were like one-dam animals, but apparently they make multiple dams

so that they can create like a whole lake area for themselves to build a little house in. And there's tons of benefits to this, like reducing erosion, controlling floods. There's a lot of like filtration that's happening because of the dams, like even removing like pesticides and herbicides from the water. But the raised water level is also covering soil that was previously not underwater. There's carbon trapped in that soil and it can dissolve into the water and it can go several places, one of which is the atmosphere. And as temperatures, global temperatures have been increasing, beavers have expanded their habitats northward. And so some places they're building dams in areas where there's permafrost. And so it's raising the water level onto this permafrost, which thaws it

out and releases the carbon there. But it's also complicated because the beaver ponds also have carbon storing effects. They're putting a bunch of biomass underwater, like the trees, and also in the soil that they're covering up. And that biomass is storing carbon. So basically, beaver activities have some carbon-releasing effects, and they also have some carbon-storing effects. There was a paper in mid-2018 that found or estimated that overall, beavers are releasing twice as much carbon as they're storing.

No. Well, they're doing better than us. Yeah. I would guess that we are releasing far more than twice as much than we are. But they're like in second place in terms of animals. Yes. It's a complicated situation and we don't like 100% know. Like it's all estimates.

And humans are still way, way, way worse than beavers. But I just thought it was funny to think of like how we're not the only species that's like doing things that are affecting climate change in some way. With a net increased carbon. Yeah. Building things and fucking everything up. Is there anything else that would like any other animal besides us and beavers that make carbon happen make it well i mean i'm not gonna like let's discount everything that is controlled by us so obviously cows do but like they wouldn't be doing it if they weren't for us okay but i think you could probably say

the same for a lot of ruminants that produce a lot of methane probably you know have a net positive effect on global warming but like it's to be so minuscule compared to, like, one airplane flight. Look, we got to blame everybody else first. That's the only way we can get around to ourselves. I mean, I've legitimately seen people who are like, there are volcanoes at the bottom of the ocean that also spew out a bunch of carbon dioxide. And I'm like, yeah, we can't do anything about those. Plug it up.

Plug up the volcanoes. Do you want to, like, do you want to do a deep sea expedition to stop volcanoes? Yeah, just give me a big old cork. It'll go fine, I'm sure. Termites, maybe? Oh, yeah. Termites totally produce tons of methane. Same way?

Digging in the ground or what? No, the fermentation process. Them actually converting the wood, the cellulose, into digestible stuff is a microbial process that produces methane. This EPA thing says estimates of the contribution to the global budget of methane from termites vary widely

from negligible to 15%. Wow! On the high end, that's a lot. For termites. There's a lot of termites. There's a lot of termites. Yeah. But there are way more beetles, right? Beetles there are the most.

There are the most species of beetles. I don't know if there are most individual beetles because there are so many individual termites and ants. I'm not actually clear. All I know is that there are 23 billion chickens on Earth right now. Too many. Did you just finish counting them all? Too many dang chickens.

That's a lot of chickens. Yeah, way too many chickens Did you just finish counting them all? Too many dang chickens. That's a lot of chickens. Yeah, way too many chickens, you guys. Oh, wait. Isn't a huge percentage of, is it mammal life or all life, rodents? A huge percentage of mammal species are rodents. There are about 1,500 living rodent species out of 4,000-ish living mammals. And then bats are like the other big contributor to the mammal species there's like 2000

species of bats or something for now someday we'll be number one that would be a bummer but then where would all the chickens be

well there's chickens and humans we're tied for first I think that if the chickens wanted to take us over they apparently could you think so

23 million how many people are there 7 ish 7 plus yeah you're right chickens are small though what's 23 divided by 7 they apparently could. You think so? Oh, there's more. 23 million. How many people are there? Seven-ish? Seven plus? Yeah, you're right. Chickens are small, though. What's 23 divided by seven? About three.

I could kill three chickens. There's tons of people. We all gotta do our part, guys. But they're also like babies and old people. They can't take those three. But some of those chickens are babies and old people.

Hank could also kill six chickens if he had to. Especially if some of them were babies and old chickens. Hank could also kill six chickens if he had to. Especially if some of them were babies and old chickens. Take some extra for Oren. Yeah. He has his three chickens delivered to the doorstep. You have to murder them for him. They're not delivered.

They're coming at us. Oh, they're attacking. Okay, somebody has to get a Hank buck taken away, and I think it's me. Okay. I'm going to give you my Hank buck. Well, I lost it immediately me. Okay. I'm going to give you my Hank buck. Well, I lost it immediately. I'm also going to give mine to Hank. I'm sorry.

The global warming made me sad. And now it's time for Ask the Science Couch, where we ask listener questions to our couch of finely honed scientific minds, by which we mean Sari. Patty asks, why aren't there more giant rodents? This is a great question. And I don't have a good answer for that. Were there even a lot of prehistoric giant rodents?

Well, this big one in South America, which died out about 4 million years ago, is by far the biggest and is about twice as big as the next smallest. And then the one after that is the capybara. So there just never have been super giant ones besides that like those two it seems like that yes there's a giant beaver that was in north america how big is a giant beaver approximately two meters and weighed up to 125 kilograms so so almost 300 pounds not that big compared to the other guy animals kill other animals and that's like the ultimate answer to the question because of what are known as ecological niches or niches, however you want to pronounce that word. Just the way the food web is set up, there are a lot of small animals that eat things like grasses and little bugs, foraging kind of things. And then as you go up the food chain, there's less room for those animals because they need space.

They need resources. And rodents are often on the lower end of the food chain. A lot of them eat grasses. A lot of them are those foraging herbivorous kind of organisms. So in order to get really huge, they need to be or would ideally be the apex predator in a situation. But there are very big herbivores. Like the biggest animals are herbivores on land. And interestingly, like there were a lot of giant ground sloths and giant and like this big old rodent in South America.

And what is interesting to me is like what makes horses and elephants better at being big old herbivores than rodents? I feel like part of it is luck and chance and the way that these adaptations rolled out. So maybe whatever the elephant's ancestor was just happened not to be eaten enough as the babies got bigger and bigger over evolutionary time. And so then they filled this role within the ecosystem. But I don't know, even capybaras are eaten by bigger things. They're jaguars. Humans hunt them and kill them. Where do beavers fit into the food chain?

Did they get big because they learned how to build a house? I will guess and like preface it with the fact that it's a guess. A lot of the big rodents seem to be water based so like capybaras beavers nutrias they all filled i don't know this like aquatic mammal thing is is kind of a weird space to occupy because not all mammals are comfortable in the water can survive in there can build a shelter can find food in that ecosystem. And so it's possible that over time, like they just got healthier, they got bigger, and then their babies were healthier and could grow bigger. If you have everything being taken care of for you, there's an arrow towards

getting bigger because it lets you compete more effectively for resources amongst, like if you're competing with other members of your species, it often does help to get bigger. There's a really good example of that. It's not a giant rodent, but it's rodents that are giant relative to their size or like the normal size. On Goff Island, house mice are like 150% their normal size.

So like there's an arrow. There's an arrow. Something pushed them to get bigger. Yes. And it's because I think there aren't that many humans on the island. They were allowed to run rampant and they started eating Atlantic petrel chicks. So they started eating bird chicks. And in order to compete with that, I think we're like not entirely sure why, but they're about 10 inches or 27 centimeters big. And the chicks are still bigger than them, but they're about 10 inches or 27 centimeters big. And the chicks are still bigger than them, but they just grew to get big enough to start like attacking these baby birds and eating them.

Yeah. And now, according to this paper, which is buck wild to me, of the 1.6 million petrel chicks born each year, an estimated 1.25 million of them are eaten by mice. By these like giant tiny mice you guys stop it i know where this is going i've heard this story before they're just like us too and so that's an example of something that is small like a house mouse that just ended up on an island bred really fast found a food source didn't have anything really eating it and then

bleh yeah they're gonna drive themselves to extinction no problem they're gonna have to start getting small real fast alright

so if you wanna ask the science couch a question you can tweet us your question using the hashtag ask scishow thank you everybody who did that

including color me trash 2 and cat loving london our final hank buck scores sari you have won I have won Thank you to everybody who did that, including Color Me Trash 2 and Cat Loving London. Our final Hank Buck scores. Sari, you have won. I have won because I went on a dumb tangent and I could have been tied for the win. Stefan, you have won, and Sam is our winner. You're a bunch of losers.

That's why you encouraged the tangent. No, no, I won completely naturally. It doesn't matter how you win, Sam. It matters that you do. If you like this show, and you want, it's America, and you want to help us out, it's really easy to do that. First, you can leave us a review wherever you listen, like Amber Loves Pods did.

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I've been Stefan Jin. And I've been Sam Schultz. SciShow Tangents is a co-production of Complexly and WNYC Studios. It's produced by all of us and Caitlin Hoffmeister. Our art is by Hirokumatsu Shima. And our sound design is by Joseph Tuna-Medish. Our social media organizer is Victoria Bongiorno. and we couldn't do any of this without our patrons on Patreon. Thank you, and remember, the mind is not a vessel to be filled, but a fire to be lighted. But one more thing.

Capybara have anal pouches, which are described in males as dry and bristly. What's it do? It is a scent receptacle. There is a great picture on the internet of a capybara that has inserted a stick into its scent pouch.

No. Just like gotten right up into the capybara's pouch. It's like, I'm going to make this smell real nice. Yeah, and it's how they communicate and they all have different scent smells and it's not unusual,

of course, but does feel a little bit grody. And they really like to put their nose scent glands on each other's anal pouches

and mix the smells together.