How Frogs Work | Stuff You Should Know Podcast (Transcript)
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How Frogs Work | Stuff You Should Know Podcast (Transcript)
Length: 54 mins
Welcome to you Stuff You Should Know, from howstuffworks.com.
Josh Clark: Hey, and welcome to the podcast. I'm Josh Clark and there's Charles W. "Rivet" Bryant. There's Jerry "Budweiser" Roland.
Charles W. Chuck Bryant: [Laughs] Oh man, that's aÔøΩ Old call back. The Budweiser frogs.
JC: Yeah, man. They were no Spuds McKenzie, I'll tell you that.
CB: I know. Remember when they were on their lily pads going, "Wassuuup!
JC: Oh, yeah, I loved that guy, those guys. Man, we've seen a lot of ads in our lifetime, haven't we?
CB: We've recorded a lot of ads in our lifetime.
JC: We have, we've really been contributing to the pile. How you feeling?
CB: I'm feeling great.
JC: You're feeling froggy?
JC: I'm really sorry. I had no idea this was gonna happen.
CB: I am feeling froggy and, right off the bat, we should go ahead and thank Tracy "TV" Wilson, Tracy V. Wilson. From Stuff You Missed in History Class, because this is one of her great, great animal articles.
JC: Yeah, she's written the best.
CB: She really has.
JC: This one doesn't contain the words "mouthÔøΩ" What was it mouth?
JC: Mouthparts, that's right.
CB: [Laughs] Yeah, she tried to work it in.
JC: It got edited out, I think.
CB: [Laughs] That's right.
JC: So we are, we're talking frogs today, Chuck. I can't believe we haven't talked about them before.
CB: I know. I love frogs.
JC: I love them too and it's sad for us then because it turns out that frogs, apparently, are going extinct at an alarming rate; entire species just dropping off the face of the earth. In fact, one species went extinct here in our fair city of Atlanta. Did you know that?
CB: Oh, really?
JC: Yeah, last September 2016, so about a year ago. The very last Rabb's fringe-limbed treefrog died at the Atlanta Botanical Garden.
CB: Oh, wow.
JC: His name was Tuffy and, from what I understand, he didn't like to be handled. That that was his choice, you know? So he was the last of it. The species was found, I think, in the late 80s or late 90s and we figured out, pretty quickly, that they were endangered, and the last one that was heard in the wild was in, I think, 2005. And so they thought Tuffy was the last one and so a frog species went extinct in Atlanta. And, apparently, that's just one domino out of many.
JC: That's going on right now. There was a study from 2015 that concluded 3%, which is about 200 species, of frog species have gone extinct since the 1970s, right? Which is like, "Wow, that'sÔøΩ" Seems like a lot. Prepare for it to seem like even more. You're ready for this?
JC: So amphibians and reptiles have really high extinction rates as it is. They, apparently, have an extinction rate of about 10,000 times other animals.
JC: And frogs' extinction rate is higher than most other amphibians and reptiles. So the frogs are going fast and the reason why it matters, besides the fact that we love frogs, is that they're also known as an indicator species. They're particularly fragile, they're found all over the world, and they seem to be trying to tell us that the earth is going lopsided as far as the global ecosystem goes.
CB: That's sad.
CB: Remember, we talked about those and, I think, it was Charismatic Megafauna?
JC: Yeah, I guess so.
CB: All right. So, we might as well get into this. I almost said jump into this, but now I'm hyper-aware of bad frog puns.
JC: Yeah, sorry for everything.
CB: So Tracy makes a great point here. Talking about frogs, and if you just said there, what 3% of different species is 200?
CB: So that shows you how many different species there are.
CB: It's difficult to kind of talk about frogs in one big sweeping way because they differ so much species to species. They can be, what is it, the Gold Frog is less than a centimeter.
CB: Then you have Goliath Frogs.
JC: Oh, man.
CB: That are over a foot.
CB: Head to tail.
JC: A foot? 32 centimeters?
CB: Yeah, a lot of them like to be out at night, some of them are more active in the morning and the afternoon, sometimes they live for a couple years, sometimes they live, well, not many, many years, but several years.
JC: Yeah. One of the main things that frogs are known for, which is croaking or ribbiting, it would seem like that's universal; it's not. There's plenty of species that don't make any noise.
CB: Yeah, you think of green or brown, there are pink frogs.
CB: All kinds of colors, there are blue frogs. The difference between toads and frogs isn'tÔøΩ We might as well just consider them one thing from what I can tell, right?
JC: Yeah, toads, true toads belong to the Bufonidae family.
JC: So toads are frogs. But even within that distinction, there are some things that are like, "No, that's actually a toad." Like, toads tend to have eyes that are lower on its head.
JC: And more football-shaped, whereas a frog has eyes higher up on its head and they're usually quite round, right? But there are certain toads that have those kind of eyes and there are certain frogs that have toad-like eyes. You can't pin frogs down.
CB: Unless you're in science class. [Laughs]
JC: Right, even with their tails. That was great, man, by the way.
JC: But even with their tails, right? So their order, like I just said, ÔøΩ ÔøΩAnura, means tailless.
JC: And it separates them from the other amphibians, the fact that frogs don't have tails across the board. Actually, no; there's two species that have tails.
CB: Yeah, they're very vexing. There's a coastal tailed frog and the mountain tailed frog, and I looked them up. You know, they're little tiny tails and they are the reproductive organs of those species.
JC: It's a penis, then. I don't understand why they don't just call it the penis frog. There actually is a scrotum frog. And get this, there's a scrotum frog population at Lake Titicaca.
JC: You can't make this up. This is what frogs are here for. It's just to say amazing things.
CB: Here's one thing I didn't know, and we're gonna be dropping in frog facts throughout, they molt. I had no idea that frogs can molt. Every two days they can molt.
CB: And they start out by eating their own skin around its mouth. They basically eat the skin around the mouth then pull the rest of their skin over their head like a dirty tee shirt, and then they eat that like a dirty tee shirt.
JC: Right. Imagine that, man. You know when your lip gets chapped and you kind of bite it, like a little piece, and you pull it off and it's likeÔøΩ
CB: I'm doing that right now.
JC: Oh man, it's a little raw.
JC: Imagine if that piece was your whole skin.
JC: And then you'd be a frog.
CB: [Laughs] Or a toad.
JC: Either one.
CB: I think I'm more down with the toads because frogs are generally the slicker skin.
CB: Toads are the ones that kind of have the bumpy, drier skin and I think they're the ones, when you pick them up and look at them, they stare into your soul right back at you trying to talk.
JC: The toads do?
CB: I think so.
CB: Am I getting that confused with frogs?
JC: I don't know. Have you ever kissed a frog?
CB: [Laughs] No, but I would.
JC: Under what circumstances?
CB: I don't know. A couple of drinks.
JC: [Laughs] A frog or a toad?
JC: Or would you kiss either one?
CB: I would kiss a toad, but then I would be a little, just because I love animals and think they all deserve affection, but I would notÔøΩ I would think twice, and we're gonna go over this later, but licking a frog for hallucinogenic, good times.
JC: Yeah, you might want to think even more than twice.
CB: Yeah, I would not want to go down that road.
CB: But we'll get to that. I think you can kiss a frog and not necessarily hallucinate.
JC: You can. You just have to plant it right on its big old mouth.
CB: That's exactly where it goes.
JC: And if the frog really likes you, he'll be like, "Here, take my skin. I was gonna eat it myself, but you can have it."
CB: [Laughs] The reason why I made that bad but good science joke about pinning frogs down is they are one of the go-to animals that you will dissect in school. And the reason why they're one of the go-to animals, it's not just because teachers hate frogs or that teachers love frogs, but it's that frogs, they're trying to teach kids about internal organs and not that of a frog; they're trying to teach them about themselves because it turns out, when you cut open frog, you might remember this, it's not a circuit board or a series of balloons or golf balls. When you cut open a frog, there are heart and lungs and a stomach and a pancreas and a gallbladder and intestines and a liver.
JC: Yeah, largely connected in a way that's similar to humans.
CB: Yeah, just all packed in that tiny little guy.
JC: Yeah, I mean they're all tiny organs.
CB: Very cute too.
JC: Appropriately sized.
JC: They are cute. Remember that smell, though?
CB: Of the formaldehyde?
JC: The formaldehyde stink of death. Man, that was not a good smell.
CB: That was not good.
JC: And so beyond just the internal organs too, Chuck, if you look at a frog's skeleton, especially its arms, its extremities, it bears a resemblance to human anatomy as well, right?
CB: For sure.
JC: You've got a humorous, a radius, and an ulna, just like with your arm. And then the frog's legs and back, they have a femur, a tibia, and a fibula, just like your legs too.
CB: Yeah, the only difference is the radius and ulna are fused and the tibia and fibula are fused.
CB: Whereas they are not in our bodies.
JC: And they have a scapula and clavicles.
JC: Collarbones and shoulder blades too, right? So they're just basically little people with big mouths.
CB: Sort of.
JC: Well, there's actually some big differences too.
CB: They have fingers and toes.
JC: They do. They have, usually, and again it's tough to generalize here, but a lot of frogs have four fingers on their front feet, and five on their back.
CB: Yeah, and these little digits are gonna vary from species to species according to what the frog's locomotion needs are.
CB: So if it's a tree frog, they're gonna be long and flexy so they can grab stuff, if they're swimmers, and all frogs and toads, we should point out, need water to live.
JC: Yeah, we really have to get into that part.
CB: Which we will. But they have little webbed feet and toes, of course.
JC: Yeah, it makes it easier for them to swim.
CB: And what about the little burrowers?
JC: Yeah, some of them, I get the impression that they burrow to hibernate or estivate.
JC: Emilio Estivate. [Chuckles]
JC: We're feeling silly today, huh?
CB: I was watching Breakfast Club last night for the first time in years.
JC: How was it?
CB: It holds up, and I know that movie by heart, it's really remarkable how well I know that movie.
JC: But it does hold up?
CB: I think so.
CB: The only thing thatÔøΩ T's not a very diverse movie likeÔøΩ
CB: You know, it's five white kids and a white principal.
JC: Throwing a little bit of casual racism here there.
CB: Yeah, but I mean, you know, John Hughes has been accused of that in recent years.
JC: Oh, really?
CB: Yeah, just sort ofÔøΩ
JC: Oh, Long Duk Dong was his too, huh?
CB: Of course. And the only time there were people of different ethnicities in his movies, they were kind of joked about or aped.
JC: Yeah. I'm sureÔøΩ It's funny how history can just turn on you, you know?
JC: He was probably like, "Wait, no. Everybody loves me; I'm John Hughes. What do you mean?"
JC: "We all thought this was great, don't you remember? I'm John Hughes, don't you know me?"
CB: [Laughs] Yeah, it's very sad.
CB: He was gone too soon. Where were we? Oh, Emilio Estevez.
JC: Oh, yeah. They Emilio Estivate, which isÔøΩ
JC: Like hibernation in warm temperatures or hot temperatures, when it gets so hot out.
JC: That, for all intents and purposes, you can't go hunt. You're just like, "It's too hot."
JC: "I'm gonna dig myself a little hole and lay here until it cools off a little bit."
CB: Yeah, and the whole point of that was that their feet and hands are shorter and wider like shovels. And like Emilio Estevez, ironically. [Laughs]
JC: Yeah, that guy can dig a hole faster than anyone you've ever seen.
CB: What are some of the different things? They don't have necks. If you look at a frog, he doesn't have a big long neck that turns around and looks at you; they're just sort of these little squat heads sitting directly on their bodies.
JC: Yeah, like Fred Flintstone.
JC: And, as a result, they can't turn their heads, right?
JC: They can't lift them up or down or turn them.
CB: If a frog ever turns his head and looks at you, then that is a evil possessed frog.
JC: [Chuckles] Right. Which, if a frog sitting there staring at you, especially if they're suddenly joined by some companions, you should probably run away.
JC: There's just something super creepy about them. I can't remember the movie, Chuck. What was the horror movie that features lots and lots of frogs?
CB: Oh, I don't know.
JC: It's like the point of them. I can't remember the name of it. It's from the 80s, I believe.
CB: I don't know.
JC: I will happily respond to anybody who writes in.
CB: Was it The Day the Frogs Took Over?
JC: [Laughs] That's right. The Day the Frogs Stood Still.
JC: Frogs! With an exclamation point.
CB: [Laughs] What else? They don't have ribs, they have a pelvis that can slide up and down to help them jump.
JC: I thought that was pretty cool.
CB: Which one, the pelvis?
JC: What, it has a hole in it and it slides up and down the spine?
CB: I think so, so it can help it jump.
JC: Yeah, I think that's pretty cool.
CB: And what else?
JC: They haveÔøΩ Well, their eyes, Chuck, the eyes.
CB: Oh, yes.
JC: Like I said, frogs typically have eyes that sit on the top of their head and they can see quite well in a very wide angle. They have a wide wide view.
JC: Vantage point. Could've put that better, but that helps compensate for the fact that they can't turn their heads, right?
JC: But apparently, as Tracy says, what one eye is getting in information is not really overlapping with the other eye, so they don't have binocular vision; they have vision from two different eyes. And it sounds like, "Okay, whatever. Who cares?" But if you think about the depth perception it would take to pick a fly out of the air with your tongueÔøΩ
JC: It suddenly becomes quite impressive that they don't seem to have binocular vision.
JC: And have did you do any research on their tongue?
JC: So, Chuck, their tongue, right?
JC: They don't have a tongue that's anchored to the back of their mouth like we do.
JC: It's anchored to the front and they can throw it out. And there's this one researcher, who I think is working out of Georgia Tech, who filmed leopard frogs. The leopard frog can catch an insect with its tongue in 0.7 seconds.
JC: Which is five times faster than humans blink.
CB: Holy cow.
JC: Right. So researchers wanted to know how are they doing that? If you're hitting on a fly with your tongue, you're gonna knock it away from you. How do they grab it?
CB: It's sticky, right?
JC: They figured that, yes, there was something sticky and they determined that frogs' saliva is a non-Newtonian fluid, which, remember we covered that.
CB: Oh yeah.
JC: In the ketchup up episode. And just like ketchup, a frog's saliva can turn sticky or it can turn less sticky when you apply force to it. So when the tongue, and the saliva on the tongue more importantly, comes in contact forcefully with an insect, it thins out and it covers the insect. But the moment it starts coming back and the force reverses, and I'm sure I just got that wrong.
JC: I'm gonna hear about it, about physics from everybody.
JC: But once it stops being thin, it goes back to being viscous and somewhat sticky, and so now the fly or the insect has been covered in the sticky goo and is attached to the tongue and is being brought back into the frog's mouth.
JC: All that happens in less than 1/800 of a second.
CB: That's crazy.
CB: I'm sure they have some pretty super cool slow-mo.
JC: Yeah, they do for sure.
CB: Well, but since you mentioned the tongue, though, because it isn't anchored in the back of their mouths, they can't use the tongue to push food down. So when a frog eatsÔøΩ They also don't have a jaw that they can chew, like you would think and like humans do.
CB: So they just swallow it in a couple of gulps and they actually, since they can't use their tongue, they use their eyeballs.
JC: [Laughs] Yeah.
CB: Their eyes sink into the skull to push food down.
JC: So I just have to ask, Chuck. Where do frogs stand in relation to jellyfish and octopi now?
CB: Oh, wow. Not ahead of those too.
JC: Okay, so third, fourth, fifth, seventeenth?
CB: Well, if we're talking all animals, I don't know where to rank them, but if we're talking crazy Stuff You Should Know animals, I would go with number three.
JC: Got you.
CB: For now.
CB: And on those eyes, they have what's called a nictitating, is that right? Nictitating membrane. You've probably seen when frogs or toads go to dive underwater, they have a film likeÔøΩ What's the other animal that does that? Seems like we talked about that.
JC: We have.
CB: They have a film that covers the eye.
JC: I think alligators, probably?
CB: Oh, that sounds about right.
JC: Yeah. I think that's right, yeah. Which would make sense because alligators are reptiles.
JC: And these guys are somewhat related to reptiles.
CB: All right. So that's a lot of initial frog stuff, frog body stuff. So let's take a break and let's talk a little bit more about frog body stuff. [Chuckles]
JC: All right.
JC: All right, dude, so we're back. We were about to talk about frogs getting it on.
CB: Well, quickly though, we never mentioned the ears.
JC: Oh, yeah, that's a big one.
CB: You probably noticed that frogs don't have these big, funny ears that stick off their head.
CB: They do have ears; they're just not external.
JC: That'd be hilarious.
CB: They just have the littleÔøΩ [Laughs] That would be funny. They just have the little tympanum, the little eardrum behind each eye.
JC: Yeah, and you can, apparently, if you know what you're doing, in most frog species, tell whether a frog is a male or female based on the size of their tympanum to their eyeball. In a male, I think the tympanum is bigger than the eye and, in a female, it's either about the same size or smaller.
JC: So there you go, now you know, frogs.
CB: And finally, we would be remiss without talking about the vocal sac because frogs and toads are most known, at least to me, for that great, great sound they make in the evening time in the American south and all over the world.
JC: Yeah. It's pretty awesome. So you know, you've seen pictures and video of a frog's, their skin under their chin just suddenly turns into a huge bubble?
JC: So what they're doing right then is they're taking in a tremendous amount of air and they're holding it in their air sac, right?
JC: And they're moving it, keeping it in their air sac, they're not releasing it, but they're moving it around across their vocal chords. That's what makes the ribbit sound or the croaking or the trilling sound.
JC: It's pretty awesome. One of the reasons why they're making those sounds, or at least one of the sounds, is they're attracting a mate, right? They're talking to one another, they're saying, "Hey, what do you think?"
CB: Yeah, and that sound can be everything from a croak to a ribbit to there's this, I don't know, there may be more than one species, but there's this one I've heard this summer that sounds, and I've heard people call the police, because it sounds like a child that's in danger.
JC: [Chuckles] Yeah, can you do an impression of it?
CB: No. I wish I could. It's just super loud and it sounds like a child that's hurt. It's like a screaming sound.
JC: Oh, I've not heard of that one.
CB: Oh, man. It's crazy sounding.
CB: Yeah, I'll send you a link. I bet there's a YouTube recording or something.
JC: It's like peacocks going, "Heeeelp!"
CB: [Laughs] Yeah.
JC: It's off-putting, isn't it?
CB: I still say that to this day because of you.
CB: Because we have a neighborhood peacock that I've talked about.
JC: So, Chuck, when frogs are making these mating calls, right?
JC: They're saying, "Hey baby, how's it going?" And the frog might come over or the, the male frog might say, "I like your look. I'm gonna climb on top of you, how about that?" And there's actually, because frogs are, in a lot of cases, not sexually dimorphic, like you can't visually tell the difference between a male and a female frog of that species.
CB: Apparently, that extends not just to us humans but to frogs as well because there's something called a release call to where if a male frog has mounted another male frog, the male frog that's been mounted will have a release call saying like, "I'm a dude, buddy. Keep looking."
CB: Yeah, actually, they've actually recorded that sound in nature.
JC: Oh, yeah?
CB: And I think it's something like, "Whoa, whoa, whoa, whoa!'
JC: [Laughs] Right.
JC: "I like you as a friend."
CB: [Laughs] Yeah.
JC: So the frog will move on. It's funny that they get confused just from looking as well and that it takes a reactive.
CB: Yeah. [Laughs]
JC: Process to handle that, you know?
CB: Yeah, it's called the amplexus, which is the position that they're in.
JC: Yeah, that's the mounting position.
CB: Yeah, and the male literally gets on the back and clasps the forelegs around the lady frog's middle.
CB: And they can stay there for days like that.
JC: However long it takes.
CB: Pretty much.
JC: It's just a sensual seduction.
CB: [Laughs] Basically just waiting for the female to release her eggs. As far as reproduction goes, and this is something tha