The Weirdest Thing I Learned This Week - Drunk Monkeys, Heroic Rats, Forehead Teeth

Episode Date: October 8, 2025

Carly York joins the show to talk about the most heroic rats you'll ever meet. Plus, Sara Kiley talks about some drunk monkeys, and Rachel gets into sharks' toothy foreheads. The Weirdest Thing I Learned This Week is a podcast by Popular Science. Share your weirdest facts and stories with us in our ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠Facebook group⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ or ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠tweet at us⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠! ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠Click here to learn more about all of our stories! ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Links to Rachel's TikTok, Newsletter, Merch Store and More: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠https://linktr.ee/RachelFeltman⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠  Rachel now has a Patreon, too! Follow her for exclusive bonus content: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠https://www.patreon.com/RachelFeltman⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Link to Jess' Twitch: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠https://www.twitch.tv/jesscapricorn⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ -- Follow our team on Twitter Rachel Feltman: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠www.twitter.com/RachelFeltman⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Produced by Jess Boddy: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠www.twitter.com/JessicaBoddy⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Popular Science: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠www.twitter.com/PopSci⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Theme music by Billy Cadden: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠https://open.spotify.com/artist/6LqT4DCuAXlBzX8XlNy4Wq?si=5VF2r2XiQoGepRsMTBsDAQ⁠⁠⁠⁠⁠⁠ Thanks to our Sponsors:  Visit ⁠https://GrowTherapy.com/WEIRDEST⁠ today to get started.  Go to ⁠https://Quince.com/weirdest⁠ for free shipping on your order and 365-day returns. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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And while most of the stuff we stumble, Cross makes it into our articles, we also find plenty of weird facts that we just keep around the office. So we figured, why not share those with you? Welcome to the weirdest thing I learned this week from the editors of popular science. I'm Rachel Feldman. I'm Sarah Kylie-Watson. I'm Carly York. Carly, welcome to the show. Thank you. Would you tell our listeners a little bit about who you are and about the awesome book you just put into the world? Sure, thanks. So I am I am a scientist. I'm an animal physiologist and a biology professor. So I study how animals' bodies have adapted to be in different kinds of environments. And I have studied a wide variety of animals. I've done some like horse stress physiology. And then I decided I wanted to study squid after that, as one does. And now I'm doing some sensory work with frogs. So yeah, a lot of different kinds of animals. But I have also been writing. I still, I have a

hard time calling myself a writer, but I guess I am. So my latest book is the salmon canon and the levitating frog. And it is about the value of curiosity-driven research. So this is research that does not have an immediate application and it might take decades for us to know like how it's useful if we ever do at all. But it's incredibly valuable this research. And the book came out at a sadly prussian time because we're seeing like massive cuts to this kind of research. So I didn't know that when I started writing it, but we're not in a great place right now. You want to know something crazy, I actually have a tattoo of a squid riding a horse. No way. Yeah, yeah. It's a reference to something in.

And not really going to be able to say it, but there's a squid on there. It's a reference to something in Carmen Maria Machado's memoir in The Dream House, which is one of my favorite books. But when you went from horse to squid, I was like, my God. I feel like we're connected. Yeah, yeah, exactly. Well, anyway, we're excited to have you on the show. So let's get right into it. So on the weirdest thing I learned this week, we start by each offering up a little tease about some kind of fact or story we found in the course of reading, writing, reporting, et cetera.

decide which one we just absolutely have to hear more about first. Then once we've all had time to spin our little science yarns, we reconvene and decide but the weirdest thing we learned this week actually was. Though today I feel like the weirdest thing we learned this week is that I have a tattoo of the two very distinct animals that you have studied. Sarah Kylie, what's your teas? Okay. So mine is that wild shrimps quote unquote drink alcohol every single day.

Yay! Good for them. I get it. I understand. My tease is that there are fish with teeth on their heads for sex reasons. Nice. Yeah. And good for them.

Carly, what's your teeth? Well, mine isn't nearly as spicy. I'm just going with rats save lives. I mean, also good for them. Thank goodness for them. It's surprising. It's surprising. Maybe more surprising than the other two.

Sarah Kylie, would you kick us off with drinking juice? Yes, of course. Oh gosh, I'm so excited about this one. Yeah. So this is a big topic, which lots of people have lots of opinions about. But I'll start with us, with us primates, humans. Because we and alcohol go way back, like really, really way back. And that is like an evolutionary perspective, not just like people have been brewing up mystery beer for thousands of years.

So like 10 million years ago. Basically, this study that came out about a decade ago, researchers found out that this common ancestor to humans, chimps, and gorillas, this, yeah, 10 million years ago, this creature that is our ancestral cousin, had an enzyme to break down alcohol. So basically, this is kind of like, alcohol's been a part of our existence, even before humans were humans. And this kind of makes sense, and it will start to make even more sense as we dive into it, because stuff ferments in the wild. You know, in a world where we don't have, like, perfectly curated bananas on the shelf for you to go grab, you're going to probably end up eating some fermented fruit because fermentation is just what happens when yeast and sugar molecules get smushed together and the molecules kind of produce alcohol to say, like, back off! And it creates this, like, antibiotic material and it accumulates at low concentrations

and fruits and nectar. So that's just, you know, part of being a something that eats fruit and nectar. that you're going to bump into some alcohol. But this discovery, along with, you know, decades of research has kind of led to this hypothesis called the Drunken Monkey Hypothesis, which was first proposed by Robert Dudley, who's a UC Berkeley professor back in 2004, and he published a book about it in the same year as the 10 million-year-old alcohol enzyme study. So 2014 was a huge year for people at alcohol, which ironically was my freshman year in college. So a huge year for humans and alcohol in my book.

But the idea goes like this that alcohol is routinely consumed by all animals that eat fruits and nectar. Like even, you know, birds and things, I get a little bit of alcohol. And there's a couple reasons why this, obviously, fermenting on its own. And that also, like, fermented in fruit and, you know, wine, all of these things that have alcohol in them smells. And it basically gives off this smell that's like, hey, like fruit that's just a problem. about to be not good anymore over here. Delicious. Come gobble me up. And of course, there's also the element of that we're, you know, still like maybe in the process of being studied, especially in other animals, is that alcohol makes us happy. You know, we are happier, we're more social,

we get that boost in energy. And so Dudley wrote about this in courts a couple years ago, but like for animals searching in a rainforest for nutritional resources that could be scarce, it's a good idea to consume these ripe fruits as quickly as possible before the competition arrives. So lots going on in the world of our monkeys getting drunk. And at first, people didn't really think that this held a ton of water, but there's been a lot of developments in terms of watching our evolutionary cousins consuming alcohol in the wild and in captivity. And so a couple examples of those.

So scientists at the University of Exeter recently captured this footage of wild chimps kind of eating and passing around African breadfruit in West Africa and at least 10 different situations. So there's like some like monkey alcohol hangouts going on very recently. And in 2016, Dartmouth researchers found that they were doing some experiments with two eye eyes and a slow loros, which I'll explain what those things kind of are. But basically they found that these creatures, which are our evolutionary cousins, although IIs are from Madagascar, so they're in a league of their own, but they still apparently have this 10 million-year-old, hey, enzyme for breaking down alcohol.

But they could tell which nectar samples had more alcohol, and they wanted those. So that's fascinating stuff. And then basically... I want to go to a wine tasting with an I-I. Oh, my dream, my actual dream would be to do that. And I'm like, there's so many things. I want to now do all of these. I want to go to Napa Valley and watch people drink alcohol now.

Now that I've researched this. But, yeah, so, and basically, so Dudley and his team is also, they're also doing a bunch of this research, obviously out of UC Berkeley. And a couple years ago, they found that Panamanian black-handed spider monkeys go for fermented fruit in the wild. Like they prefer to find the more fermented fruit in the wild. And then they tested their urine and they saw that like the alcohol is being metabolized. So it's not just like, they're not just peeing it straight out.

Like they're using it for energy, yada yada. So there's all of this research where we're kind of learning more about what our, yeah, our evolutionary cousins are doing in terms of alcohol. But the key driving question behind all of this is not are they eating alcohol-laden stuff, which in many cases, yeah, that appears to be the case. But are they like actually getting drunk? Is anyone acting sillier after having a little gathering with your, your chimp friends and sharing some lightly rotten fruit.

But yeah, so the latest drunk monkey shenanigans kind of came out a couple weeks ago. It's a new study. And this time it's all about chimps, which they haven't been looked at as much. Clearly, we had that study from a couple months ago. But like I mentioned, it's like eye eyes and spider monkeys and all these other guys. But chimps are our closest buddies. We only diverged from them like 6.5 to 7.5 million years ago, which in the grand scheme of things is not that long. but yeah, human and chimp DNA is like pretty much like almost,

it looks almost identical if you like line it up and it's like 99.8% the same. So we're very, very tight with chimps, which, you know, it's always fun to think about. But yeah, so basically this time it's Dudley's team and some other researchers, of course, and they followed around a group of wild chimpanzees in two different locations in Uganda and on the ivory coast. And basically what they did was like, yeah, like lurked around, watch the wild chimps do their thing. And they scooped up samples of the fruit that they saw these wild chimps go for, basically like the undamaged, freshly fallen fruits on the ground near the trees that had been recently forged by chimps.

So basically we're, yeah, scooping up chimp leftovers. And then they kind of tested for alcohol content using, like, there's one device that's like a breathalyzer. They had a chromatograph and a chemical test. So a bunch of different ways to say, like, how alcohol-filled are these fruits anyway? So what they found is that in the course of a day, wild chimps consume a, about 14 grams of pure ethanol, which is adjusting for body mass and all of that fun stuff, like about the similar amount to a human having more than a drink a day or a drink in some.

And these fruits have like an average alcohol content of around 0.26% by weight, which doesn't sound like a lot. But when these chimps are eating 10 pounds of fruit a day, which is like 7 to 14% of their body weight, that adds up. And on top of just the generalized alcohol fruit of it all. The chimps kind of preferred this fig and this plum at the respective locations that were the highest alcohol content. So not only were they having a little booze with their fruits, they were preferring the ones that are even boozyer. And there's a couple interesting things to unpack here. And obviously the first is the question of if the chimps are getting drunk from this and it doesn't really look like it is what the others say. Like nobody was acting. Well, they're getting so much fiber.

Right. Yeah. It's just it really seems like they have no choice but to pace themselves. And that's exactly it is that like, whereas we, we can have as much alcohol as you can take because it's not filling you up, right? But like if you're eating fruit, like you're going to be so bloated and sad if you try to have more than like this amount of alcohol. And at the end of the day, if it's like a, you know, like a beer a day and it's like spread out throughout the whole day, it's just nothing.

It's like you would not feel that unless you are like, it's, it's, tiniest person on earth. So, I mean, who knows? Maybe. But I don't think I would. I would be too distracted by the eating. So that's basically what's happening is they're being very responsible with their food to alcohol ratio and therefore not getting wasted in the jungle all the time. But yeah, so now they're kind of doing this like next, the second part, which was kind of like with the spider monkeys where they're now catching the pee, which is fascinating. It sounds like it's like you kind of like have to like actually walk around with like an umbrella catcher of pee under the chimps to get the pee, or you have to like pipette it off of leaves.

It sounds like it's a whole thing. But now they're figuring out if like that same metabolic shenanigans is happening where it's like, okay, they're not just peeing out the alcohol. It's actually like going up and into their brains and all throughout. So we're figuring that out. But it's, I mean, seems like that might be the way that things go. But the other part is, again, that these chimps are wild. These are not like in a zoo somewhere.

and the diet of a wild chimp versus a chimp in captivity is really, really different because chips in captivity are not doing a ton, so they're not eating a ton. And also they're eating, like, fruit that humans are kind of, like, have been in charge of farming. It's not just, like, jungle fruit, which has been sitting in the sun, potentially fermenting. So it just, like, kind of opens up this question of, like, are they getting the nutrient that is alcohol because they're kind of like they're like sober people like they're not like getting it in the same way that wild chips are so it kind of like opens up this question of like are they getting what they need because there are

a lot of benefits to fermented food which like alcohol is fermented food at the end of the day and in a cute bottle a lot of times because like we think about things like yogurt and kimchi and the probiotics and how that helps like your gut be strong and healthy and happy. And if captive chintz aren't getting their fair share of fermented fruits and even, again, like people, like what are the health implications of that? So that's like one of the big unanswered questions with the drunk monkey stuff. And like, so basically, but like knowing all of this, it kind of just like also opens up what it means for, like, why humans are drawn to alcohol in general. Is it an evolutionary thing? And I got to talk to the lead author of this study, which was always so fun. Alexi Morrow, wonderful, wonderful chat,

but basically some of his hypothesis is behind, like, hey, like, what does this actually mean for human evolution? And, like, human issues. Like, alcoholism is not a joke, obviously. And unlike chimps, like, we can drink kind of nonstop. We don't get full from fruit. So it's kind of just asking this question of why did we develop alcohol in the way that we did? is it filling some kind of like evolutionary mismatch is the way that he described it. Like when the ecosystem started to change and we were like, hey, alcohol means good food, like did the brewing come as part of that as kind of like a technology to help humans get through scarce or changing ecosystem times? So lots of just like really interesting opened doors from this like fascinating study of basically following around wild chimps and picking up their leftovers,

which is always fabulous. But yeah, like the moral of the story here is that, yes, chimps are ingesting alcohol. And we know that officially for the first time. But chimps out in the wild minding their business are getting, they're getting a beer. They're getting a beer every day. And are they boozing enough to act drunk? Probably not. But, you know, until we can see it all over and over and over again and keep exploring this,

It's just a conversation for a glass of wine, if I may say. But yeah, that's the scoop on the latest with the drunk chimp drunk monkey hypothesis. I love my favorite aspect of this study is just thinking about how much fiber a chimp would have to consume to have like multiple drinks a day, you know, the equivalent of. And just like how immediately unpleasant that would be from like a blois. over full perspective and how probably humans would drink less if we had more immediate, nasty feelings that having most of the nasty feelings be the next day maybe doesn't do us a lot of favors. I mean, if I had to have like four cartons of strawberries to get a buzz, then like I assure

you I would not be doing that. No, thanks. I can go without. It's quite all right. Okay, we're going to take a quick break and then we'll be back with some more facts. Did you know that there's an online cannabis company that ships federally legal THC right to your door? I'm talking about mood.com. They have an incredible line of cannabis dummies and a lot more. And you can get 20% off your first order at mood.com with promo code weirdest.

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I confess this isn't something that I just learned this week. This is something I have been dying to talk about ever since I read about them. I'm excited. I've actually, I have pitched this to a few places and I've gotten turned down. So I'm really pumped to finally get to talk about these careers. We're honored. So the rats that I am talking about, they are called African giant pouched rats. And they are not like your typical domestic rat or the one you might see in New York City.

They are quite big. They can get up to three feet long, including their tail. So they're not marsupials. They're not pouched in that way. They like to stuff food in their cheeks. And they consider that to be pouches. So they have pouchy cheeks. So there are these big pouchy rats.

And it turns out they have a really. really incredible sense of smell. And they are also super duper intelligent. So these two features together have made them actually really useful for a few different humanitarian efforts. And that's why they have gotten the name of the hero rat. They're also really cute. Puffy cheese.

Did you see one with a vest on? Yeah. Yeah. Yes. So this started with an organization. The abbreviation is Apopo, and it translates in Dutch to something close to anti-personnel landmines detection product development. Sounds about right. Sure.

And the first effort that they really took on was using these rats for detecting landmines. So they train these rats to pick up by. I smell where a landmine is and then give a little scratch to let their handler know that they've detected a landmine. And what's super cool about them is a dog could probably do this too, but a dog is heavy enough that it would actually detonate the landmine too. But the hero rats aren't. They're light enough that they won't. So they actually do weekly weigh-ins just to make positively sure that they're going to stay below the threshold that would trigger. or detaining a landmine. So they've been doing this in like really landmine ridden in places like Tanzania,

Cambodia, and Zimbabwe and others. So according to their annual report, their 2024 annual report, they have been instrumental in detecting 1,069,884 landmines. Wow. Liberating an estimated 2 million people from the threat. that they pose. Oh, my gosh. Also, this is the only time I have ever been in support of workplace wagons.

Oh, yeah, skinny rats. Normally, terrible, terrible red flag in this case. Yeah, keep those chunky guys for getting blown up. Important. It is. It is important. Oh, and I will say I have adopted several of these. And we get, oh, my gosh, I was going to put.

put a plug at the end, but I'll do it now. You can adopt these little critters. If you go to the Apopo website, they have a number of them for adoption. I think I've adopted all of them. And you get monthly newsletters that are really detailed, actually, and it tells you, you know, their weight check-in, but it also tells you their favorite treats that week and how many, what kind of, you know, work they've been doing, how is their training going? It's like the highlight of my month. Yeah, I got to check it out. This is essential knowledge.

It is. It is. So the landmine project, that's been going on for a little while now. And if you think that, like, they should win an award for their work, they actually have. There was a hero rat named Magawa. And in 2020, he received this adorable, tiny little gold medal. from the UK charity People's Dispensary for Sick Animals for his life-saving work. And apparently this is equivalent to the George Cross Award,

which is the highest award for a human who shows acts of heroism and bravery. So this is the first time a rat had ever won that award. So this is absolutely worth a Google search. There's lots of pictures with Magawa and his little gold medal. He was written up like in the New York Times. and NPR covered him, and so he got a whole lot of press. His record was that he cleared 2.4 million square feet of land, and he found 71 landmines and 38 unexploded ammunition.

So it was pretty impressive. But another one of the hero rats, a youngan, actually just broke Magawa's record. So Ronan. Ronan is just a young five-year-old, and he just broke the record by uncovering 109 landmines. Wow. So he's a rock star, and he still has years ahead of him to keep sniffing out of these dangers. So amazing stuff, and it doesn't end there. So another thing that these rats are being used for is detection of tuberculosis.

Oh. Whoa. Yeah. So tuberculosis is still an incredibly dangerous virus. Africa has the highest rates of TB in the world with about 75% of them of the approximate 1 million cases arising globally. And even though it's really prevalent and even treatable, it's often hard to get the equipment needed for detection in developing countries. So that requires some pretty. fancy equipment. It requires trained technicians. It requires upkeep on that equipment. So there's a lot to consider in terms of just like TB detection. And a lot is going undetected. For example, in Mozambique, more than half of the positive cases of TB actually go undetected. And it's especially tricky sometimes to detect it in children because they have a hard time producing enough sputum, which is a mucous saliva for an accurate test. But these rats are apparently really, really good at picking out TB in different samples. So they have these incredible olfactory systems, and they have these

neural connections that allows them to literally think with their nose. And that allows them to be able to detect the volatile organic compounds in these TB samples. So, incredibly well. So there was a write-up of a specific hero rat named Tarek, who was doing work in Mozambique in detecting TV. So the way this goes, paint a picture, there is like a big glass kind of cage and underneath the cage is a removable tray. And they can pull out the tray and And they will put multiple samples into that tray. And Tyreek will go around and he will sniff each of these samples. And he's trained so that when he sniffs TB, he'll scratch and let his handler know that he found a sample.

So it only takes him eight minutes to go through 50 samples. And that's more samples than a lab technician could test in a whole day. Wow. So they're super fast. They're also really, really accurate, though. There was a study that found that the rats' evaluations increased case detection rate by 44% compared to traditional methods. And there have been other studies that have supported that as well.

So training one of these rats, it costs between like $6,000 to $8,000. That's money, but they're relatively inexpensive to maintain. throughout their life. They're little rats. You feed them and you treat them nice. So compared to the cost of some of these other diagnostic tests, most of which are going to run up to close to $20,000 per device. And that's not even with the upkeep.

These rats are actually really significant in terms of being able to make progress in detection of TV. So according to their 2024 annual report, $642,000. 988 patients were screened for TB, and an additional 33,000 cases were detected after failing to be detected in a lab test. Wow. And because of that, another 300,000 other potential infections were prevented by having this detection. Wow.

They're incredible. They're incredible. And so these have been the two biggest ones that Apopos has been doing, the landmines and then tuberculosis. But they have two new initiatives that they have been working on as well. One is training them to detect illegal wildlife trade. So this one, the famous rat who's been working on this, her name is Jane. And she was named after Jane Goodall. she is being trained to sniff out things like giraffe hides or pangolin scales, things that are

commonly seen in illegal trade, and also any animals that might be common in like exotic pet trades. And the way that she does this, she has a little vest, and at the front of the vest is a tag. So when she's going around sniffing stuff, when she detects something that shouldn't be there, she knows to pull on the tag, and then that alerts her handler that she has found something for them to look at. The other newer initiative that they're working on is rescue rats. These ones are going to be rats that will help with search and rescue missions. So they are equipped with a high-tech backpack that has a camera and a two-way radio on it. And they're trained to go find people.

and the camera on the radio isn't on all the time that would take a lot of energy to just have that running all the time instead they have it like ready to go and then this rat too is trained to tug on a little tag on his vest and that will actually turn on the camera and the radio so that can have communication with this person that you're trying to rescue so it's pretty incredible

I highly recommend a YouTube watch of these guys. They're adorable and just like it's so heartwarming to me to see this animal that gets so much hate just be so so wonderful. And and I also got to again highly recommend adopting a rat or two in supporting this organization because not only is it a wonderful cause but also it's really fun to hear about everything that they're doing and all of the. I want to get the rat newsletters. I love the rats. Okay, this is very exciting. When I started doing, so I have a little part in my book about the hero rats, and I've been obsessed ever since I wrote this one little part, and I'm truly like, how do I write a whole

book about hero rats? It's all I want to do is read about hero rats and talk about hero rats. Like, how can I make this happen? So it comes up at like every party I attend. I'm sure my friends are tired of hearing about the hero rats, but man, they're great. Oh, I love them. All right. We're going to take one more quick break and then we'll be back with one more fact. I've been hearing for decades that the markets can solve climate change. Today, we have more incentives for market solutions than ever and emissions are rising. On this season of drilled, Carbon Cowboys, the story of three market solutions colliding in one multinational boondoggle. You got to get Bruce of the guy's credit.

They're Republican. They don't get a lot of money. Listen anywhere you get podcasts. Okay, we're back. And I'm going to get into my fact, which is about fish with teeth, not just in their heads, but on their heads for sexy reasons. So I'm already on the record as thinking. ghost sharks are rad. They all look like they belong in a timber in claymation film. There's one that looks just like zero from Nightmare Before Christmas. And another one that looks like some kind of

horrifying skin puppet that's been like stitched together from different fish, which is probably part of why this order of deep sea fish is also known as chimeras, which of course is a word that means put together from different parts. I think also the name may be a reference. to the fact that they're just generally kind of weird looking. So sometimes they'll be described as being like the nose is very frog-like, whatever. But one cool fact about chimeras in general, before we get into the main fact, is that they're thought to have these special muscle-filled pores that allow them to sense electrical signals in the water, which true sharks do have. And sharks and ghost sharks are related, but not that close related. They broke off like, I want to say hundreds of millions of years ago, but, you know, they're in the same realm.

But yeah, true sharks mostly use these special pores to hunt prey. But ghost sharks have them in like different parts of their bodies and they're also very opportunistic feeders. So it wouldn't really make sense for them to be like hunting down the movements of prey. And scientists think that they actually use them to navigate in the darkness of the deep sea. so they have like a spooky six cents kind of, which is very fitting for these spooky fish. But today I'm going to talk about a specific species of ghost shark, which is called the spotted ratfish,

which did not even think about the rat rat-wrack connection. But it can be found as deep as 3,300 feet, but it spends a lot of its time just like 100 or 200 feet below the surface. You know, it's still like a bottom dweller, but in shallower waters. And following the general corollary, that things get freakyer, the deeper you go into the ocean. These guys, in my opinion, are relatively cute for chimeras. I mean, like I said, I already think chimeras are, like, ugly cute.

But these are more on the spectrum towards, like, actual mainstream cuties. I would say they're a little closer than average. They have this brown-gray coloring, but they're, like, very iridescent. They have these white spots. A lot of times you'll see their face has. being described as rabbit-like. I don't know that I know what they mean by that, but they do have a very, like, short little snout,

and they have big green eyes. And they have these very cute, like big spiked fins on their back. Though, fair warning, that spiked fin is venomous. Okay. It doesn't hurt humans. Apparently can cause, like, a painful wound. But they try to avoid divers. They're not like, they don't want to spike you.

But they are potent enough to kill harbor seals that swallow them. So that seems to be the main purpose of them is to teach seals that you'll have a bad time if you eat a ratfish. But recent studies have focused on another feature of ratfish heads, which is the teeth that they use for sex, separate from the teeth in their mouths, which they don't use for sex, which they don't use for sex, as far as I know. Male ratfish have this forehead appendage called a tenaculum, which is also the name of a type of forcep. if you care. And they use it to hold a female close during sex. The forehead thing is unusual. The grasper part isn't.

In my book, Been There Done That, A Rousing History of Sex. I talked about how our earliest evidence of, like, penetrative sex as we know it, comes from some fossilized fish that were caught, like, side by side in the act, basically doce-doing with their graspers clasped. And indeed, the male rat fish. has a pelvic grasper to help it hold on during sex, but it also has a retractable feature on its forehead that is essentially, as friend of the pod, Sabrina Imbler,

so eloquently put it in their article on the ratfish for defector, a retractable rod tipped with a chandelier of teeth. Beautiful. Yeah, the ocean is full of wonders. And yeah, they're like seven or eight rows of these little teeth. Apparently, the tenaculum, when it's not in use, it retracts into like a little pimple-like nub on their forehead. But yeah, researchers got interested in this appendage and specifically the teeth on them

because they're different, when we say teeth, when we look at a tooth-like object, there are different things that can be going on because true sharks, actual sharks, as we've talked, about before on we're just saying are covered in dermal denticles, which are sort of skin teeth. If you remember when we had a shark scientist on, she talked about how like there's a wrong way to pet a shark because you can, it's like very sandpapery in one direction and smooth in the other because of those little little dermal denticles. But those are a different thing that grow in a different way than the teeth in their mouth. So, you know, the kind of first logical assumption might be, ah, this thing that's not in their mouth is some kind of dentical.

But other than this weird tooth chandelier that's retractable, ratfish are smooth little guys. They do not have any of the sandpapery skin teeth. So, yeah, they wanted to analyze the teeth, see what manner of teeth they were. And the other interesting thing about the tenaculum is that, like I said, only males have them and they use them in a very specific way for mating. But both male and female ratfish do grow them, but they only like continue to develop and stick around into adulthood in the males. In the females, it seems like it basically just stays as like a thing that looks like a pimple. Nice.

Great. Yeah. Yeah. So, yeah, that raised the question of like, where do they come from? Why is it there? And also, what kind of teeth is it? And so recently researchers actually went through the trouble of analyzing this tissue and they found that it has dental lamina, which is the structure where new teeth sprout

out of in the jaw of any animal that has true teeth. So they are mouth teeth. They are not skin teeth. They are mouth teeth. They are on the forehead. They are mouth teeth on the forehead. And so that's weird. That's weird than the alternative. And they did some follow-up molecular testing and they were like, yeah, there are mouth tooth genes in the forehead thinking. So confirmed, mouth teeth on the forehead. And then they also found that this is not like a recent fluke. Because again, like deep sea, weird, weird stuff happens. It would be one thing if this was just an odd mutation of this one species.

They also looked back in the fossil record and they found a related fish. from like more than 300 million years ago. And that was the oldest example they found of a tenaculum. It was closer to the animal's jaw compared to the ratfish. So it was, you know, maybe a little less kooky for it to be growing teeth. But it does, you know, it's an analogous structure. So it does seem pretty clear that the legacy of mouth teeth growing on the outside side and being part of these odd appendages is probably hundreds of millions of years old

and was useful enough to stick around. And I will say their pelvic clasper's have toothy features too, but those are more like denticles. Those are not mouth teeth. They don't have mouth teeth in pelvis. That would just be a bridge too far. But yeah, we, the sort of remaining question is what was this originally for? for because it's interesting that females seem to have like, you know, for lack of a better term,

like a vestigial forehead tooth situation that just doesn't fully develop. And they also have the pelvic grasper. So it's not like this was the only way they could have connected for sexual reproduction. So like that sort of suggests it was once for something else, but I don't know that we'll ever know what it was for. But we do know that their mouth, And that's really weird and we may just have to be satisfied with that level of information. I will also say that there is, as part of this recent study, there is like an illustration going around that I really think the ratfish has been hard done by in this illustration. It's truly the, it's just that they look, they look pretty lumpy and they're just colored a like flat brown. and IRL, they are very like shimmery, which makes a big difference.

And they also, I just think it's not a very flattering picture. I don't think the illustrator did anything wrong. I'm sure they are excellent at their job. But they really caught the ratfish on a bad day in this illustration. So if that's the first time you saw a ratfish, I encourage you to Google images of them. because despite being weirdos with retractable tooth graspers for sex, they are kind of beautiful, at least, you know, in the realm of deep sea fish that are weird looking. But yeah, that's my whole fact, the ratfish, tooth on the head.

What other mysteries could we uncover in the deep sea? Where do other fish have teeth? We don't even know. Mouth teeth. Oh, justice for their bad photo op. That makes me so sad. When I saw it in the press release, it was a little bit of a jump scare. I was like, who's, who, which ratfish is that? I don't know her. But yeah. Well, what are you a assortment of facts. Carly, thank you so much for coming on. And would you remind our listeners what your new book is called so they can find it? Yeah. Thanks again for having me. This was super

fun. My book is the salmon canon and the levitating frog and you can find it at your local bookstore but also at places like Amazon and Barnes & Noble. Woo! The weirdest thing I learned this week is produced by all of our hosts, including me

Rachel Fultman, along with Jess Bodie, who also serves as our audio engineer and editor extraordinaire. Our theme music is by Billy Cadden. Our logo is by Katie Belloff. If you have questions, suggestions, or weird stories to share, tweet us at Weirdest underscore Thing. Thanks for listening, Weirdos.

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