624. The Animal No One Loves, Until They Do

0:05Are you a chef? Are you a home cook? I can cook. He says reluctantly. I sometimes cook well. Not always. Do you happen to make a nice ratatouille? Yeah, I've made ratatouille before, but I don't have the skill, taste and feeling to make a great ratatouille. The thing is, it's just a bunch of vegetables, right? Well, yes, but no. Yes, but no, exactly. And that's the thing. Ratatouille as a theme and a title for the film. That was there from the beginning for a number of reasons. First of all, it's about rats. And ratatouille, it tells you it's a comedy because it's a silly word. And ratatouille as the quintessential peasant dish, it's just vegetables.

0:48It's stuff that you can find easily. If you know how to cook it well, it's beautiful. I'm speaking here with Jan Pinkover. I worked on a couple of the early feature films of Pixar, including A Bug's Life and Monsters, Inc. and Toy Story 2. And I got a break to develop my own feature film. That feature film was Ratatouille. It's about a rat named Remy who lives in a farmhouse in the French countryside and dreams of becoming a chef. You found cheese? And not just any cheese. Tom de chevron de pay! That would go beautifully with my mushroom! But then Remy, his family, and his entire rat tribe are chased into exile, and he winds up in the sewers of Paris.

1:38As he explores the city above ground, Remy comes across the legendary Gusteau's restaurant. The late chef Auguste Gusteau was Remy's hero. His famous book is called Anyone Can Cook. But Remy sees that Gusteau's restaurant is now run by a corrupt, tyrannical chef. And there's a new garbage boy in the kitchen named Linguini.

2:11Linguini does want to cook, but he doesn't have much talent. Remy has talent, but he's a rat. So the two of them become secret collaborators. One look and I knew we had the same crazy idea.

2:28Remy hides on top of Linguini's head under his chef's toque and becomes his puppet master chef. Together, they make beautiful food. Potato leek soup, the perfect French omelet, and a twist on sweetbreads a la gusto. It turns out that Linguini is the son of the great Gusteau, and the secret collaboration between Linguini and Remy turns out to be a big hit, as was the film itself. Ratatouille, released in 2007, won the Oscar for Best Animated Feature, and it grossed over half a billion dollars. That made Ratatouille a big outlier in Hollywood, and Remy the Rat was an outlier too. As we've been learning in this series on rats, it is a rare day when a rat is the hero of any story.

3:18Since the days of the bubonic plague, rats have been associated with death and disease. To call someone a rat is a special kind of insult. It suggests they've behaved so badly as to be subhuman. But is it time to reassess the rat's reputation? Perhaps even rehabilitate it? Today on Freakonomics Radio, we dissect Ratatouille with Jan Pinkova. In a way, Ratatouille is like ballet dancing with Nazis. We look at why rats have been so valuable to human science. Like right all the way down to DNA. And we hear a love story. Not to say anything negative about the hamsters of the world, but I think it's a different relationship.

4:03Come along for this third and final episode in our series, Sympathy for the Rat.

4:19This is Freakonomics Radio, the podcast that explores the hidden side of everything, with your host, Stephen Dubner.

4:37We humans really love some animals. Two-thirds of American households have at least one pet, most of them dogs or cats. We often treat them like members of the family. When we hear about an animal being mistreated or killed, the outcry can be as loud as if it happened to a fellow human, if not louder. And yet, in 2022, when New York City Mayor Eric Adams declared war on rats and appointed a rat czar to get rid of them, there was almost no outcry. The rat seems to have crossed some invisible border from animal to pest, even menace. But it wasn't always thus. The first rats that were domesticated, they were pets in Victorian England, and they were not thought of as negatively as we think about even pet rats today.

5:28So it was revered to have a rat on your shoulder. This is Julia Zichello. She lives on the Upper West Side of Manhattan and is an evolutionary biologist at Hunter College. But her rat experience is not just academic. During the pandemic, I got a car for the first time because alternate side of the street parking was relaxed. I kept it in one place for too long. I also don't really drive that often. So yes, when I went to start it, it didn't start. And I had to get a toad and the mechanic told me that there was bedding in there connected with rats and also orange peels. This was in the engine? This was in the engine.

6:08It was the late fall, early winter, which is just the time that they would be looking for a warm place. I thought it was really funny at first, before I got the bill from the mechanic. What did it look like inside the engine? The wires were gnawed. You can see shards or pieces of the wire and then the orange peels and some dry leaves and other things that they were using for nesting material. I know that rats are extraordinarily fertile. They have really short gestation. They have a lot of pups. Do you know if maybe your car was also a rat baby hospital as well? I don't know, but it may have been, which is, you know, kind of cute.

6:48Zichello had never thought deeply about rats until they moved into her car. And even then, her attitude was relaxed. She wasn't strongly anti-rat, nor did she find a reason to become pro-rat. But soon after the car incident, things changed. Yeah. So I inherited rats from a family member who moved to a building that could no longer have pets. The rats were already, I believe, 18 months old. I felt the same way most people would feel, the like, oh, no way kind of thing. Like, oh my gosh, their tails, everyone's so upset about their tails because they're so gross. But, you know, then I warmed to them over time.

7:28Eventually, because you're feeding it, because it's a little bit lovely, Then you end up feeling some warmth towards it. What kind of rats were your pet rats? They were two different breeds. One was a Gooty, and that was sort of silver-colored. The other was a hooded rat, which was white with just a little bit of black on their head and striped down their back. Can I have some names, please? One was named Sylvie, and the other was Pele. They were both males. So you didn't have any breeding, obviously. Correct. No offspring. You know, they were fun to watch. They were interactive. They eat a lot of different things.

8:04We had some fun feeding them the circular corn chips. They would take the corn chip like you would a steering wheel of a car and turn it around and eat it around the edges. One thing I noticed about the two pet rats is that they had different personalities from one another. Sylvie was much more bold and Pele was much more cryptic. They ate food in different ways. Pele would take the food and go into this little hidey box and Sylvie would just unabashedly eat the food out there in front of you. Do they vocalize? They did. Not a lot. Technically, rats do vocalize. It was only when they were socializing with each other or would they vocalize when they were hanging with you?

8:43Only when we were socializing with each other. They were not super vocal that I heard, and I think there are sounds we can't hear. Can you imitate the sounds that you did hear? Hmm, I don't know about that. Is it like a squeaking kind of thing? Yes, very, very light squeaking. Not like long vocalizations. They were not singing. There's been some research showing that rats can laugh when they're tickled. Those are things that you can't hear with the human ear, though there were special recordings that were showing that. Here's what those special recordings sound like.

9:21They also were very responsive to all of the sounds in the environment in the apartment. Things like the coffee grinder. I was noticing that the hooded rat was really stressed out when I was grinding coffee. So what would you do about that? I mean, I couldn't do anything. I had no room to move them and I couldn't stop drinking coffee. Did you take your grinder into the bathroom or a closet or something? No, no. I just noted it and continued on with the grinding. You know, their sensory systems are so acute. Obviously, their olfaction, their sense of smell is really good. Their hearing is really good.

9:55And they seem very sensitive to things in their environment. It did also make me think about the rats in New York City. There aren't a lot of studies about the behavior of wild rats from the perspective of the rats. One of the things I thought about after having the pet rats is that I wonder if the rats in New York City are very, very stressed. They like to be underground. When you see them skittering across the sidewalk, it stresses you out, but I'm pretty sure that they're also highly stressed. Is it possible that one partial solution to the infestation of wild rats in a city like New York would be the widespread embrace of pet rats?

10:36I don't know about the widespread embrace of pet rats, but I think the rat czar in New York, I think that she should have a pet rat. If you want to control them or if you want to love them, you have to know about them.

10:53I first came across Julia Zichello when I read a piece she wrote for a hyper-local news site called The West Side Rag. If you live on the Upper West Side and don't read The Rag, well, I don't even know what to say. Here is the first line of Zichello's piece. Almost a year has passed, and I can finally write about it. So they both passed away, sadly. One of the things that happened towards the end of their life, which also is something that's relevant to all rats, is that they aged so quickly. And they started to show signs of aging, like being hunched over, losing body fat. One month in a rat's life is equal to three years in human years.

11:34People know this because there's a lot of people, obviously, who use rats in the lab, trying to study aging and trying to make that equivalent. So they aged very rapidly. We don't really exactly know why they died. They didn't show any signs of disease that we could see. But one of the things that happened that was very sad is that Sylvie died first. And then for Pele, he was alone. So we bought him a little toy that was the shape of a rat because I knew that he would be lonely. It was a cat toy. He was not interested in the cat toy. And then he died less than a week later. This is typical of rats because they're so social.

12:12They really like to have other rats around. So Pele died, you think, of heartbreak, essentially? I think maybe, yeah. We knew that the lifespan of domestic rats is around two years, and they were two and a half years old. So, you know, they lived a good life. We certainly appreciated them and learned a lot. I want to read a couple sentences from the piece you wrote. I regularly walk the Upper West Side and spot swashbuckling rats at all hours, but other times I find them squashed. I don't exactly feel sad about the dead rats, but I also don't feel nothing. The dead rats make me think about life, death, and somewhere stuffed between the pavement and the pellage.

12:53I guess pellage is the fur of the rat, yes? Correct, yeah. There is something about love in there, too. Can you say more about that love? I will never see a squashed rat in New York City again and not think about our pet rats. I know that they are different. The rats in the wild are more aggressive. It wouldn't be the same thing as the pet rats that I experienced. But, I mean, of course you'd think about your pet. Are you going to replace them? Maybe that's unfair to say. Are you going to get more rats? Definitely not. I'm definitely not getting pet rats again. Because why? It's too heartbreaking.

13:31Their lifespan is too short. And the relationship between their charm and their lifespan is too asymmetrical.

13:41Julia Zichello, as a scientist living in New York, is by now familiar with what you might call the three main categories of rat. The wild ones who live on the streets, the domesticated ones who live in your home, and the rats that are bred to live and die in research labs. There are many studies across neuroscience and pharmaceuticals and psychology that used rats for decades. The rats that are lab rats are more genetically homogenous than wild rats. Rats and humans shared a common ancestor 90 million years ago. That's not super close, but it's close enough to have revealed things about the brain and behavior and genetics that have ultimately helped humans.

14:29So I wonder about how many people have technically been helped by that versus the number of people who have been harmed by diseases they may have acquired from a rat. What was the common ancestor? The common ancestor was an animal that lived in the late Cretaceous around the time of the dinosaurs. There's not a specific name, but we use genetics to understand how far back these common ancestors lived. the anatomy and behavior of that common ancestor was much more rat-like than it is human-like. They were likely nocturnal. Some of them may have been insectivores. And their basic anatomy was much more rat-like than humans.

15:09For all the parallels there may be between a rodent like a rat and humans, one gigantic difference is fertility and lifespan. Is that meaningful in any significant way to us? Yeah, so that makes rats good model organisms because you can have many offspring within your human life as a scientist studying them. So you can see how things translate from one generation to the next. One rat female can have up to 72 pups per year. And if we think about a rat pair, so a male and a female, and you think about them having offspring and those offspring having offspring, within one year there can be like 1 ,200 rats born just from that pair.

15:52From the perspective of controlling rats in the wild, that's a problem. But from the perspective of using rats in the lab, that's a virtue.

16:03Coming up after the break, what other virtues does the lab rat have? If you want an animal to press a lever and receive a drug, a rat is generally the better choice. And how did the rat become a lab animal in the first place? I'm Stephen Dubner. This is Freakonomics Radio. We'll be right back.

16:33In one recent year, the market for laboratory rats in the U.S. was estimated at$1.5 billion, and that number is expected to rise as biomedical research keeps expanding. The cost of a lab rat can range from around$25 a piece to a few thousand dollars for a specially bred or genetically engineered specimen. But as many lab rats as there are, they are outnumbered by lab mice. They're cheaper. They're smaller. That is Bethany Brookshire. We heard from her in part one of this series. She's the author of a book called Pests, How Humans Create Animal Villains. Especially now with the advent of CRISPR technologies that allow us to alter adult genetics and fetal genetics.

17:19We established that first in mice. We can do it in rats now, but it's very, very well established in mice. And so that really took off. Are there research projects or experiments for which rats are prima facie better than mice? Yes. In my experience, rats are better for self-administration of drugs. So if you want an animal to press a lever and receive a drug, a rat is generally the better choice because of size. Because mice are so small, it's really hard to make a lever that they can press. I thought you were going to say that mice, their hands are too small to hold a joint and that rats somehow.

17:59If you could teach them to roll joints, I imagine that the mice would just roll a smaller one. Before she was a science writer, Brookshire was a practicing scientist at the Wake Forest School of Medicine, where she got a Ph.D. in physiology and pharmacology. I studied primarily drugs of abuse in graduate school, and then I studied antidepressants for my postdoc. What were some drugs that you were giving to mice and rats? Ritalin, cocaine, methamphetamine, ecstasy, alcohol, Prozac. If you want to be really nerdy about it, I studied the dopamine serotonergic interactions in the ventral tegmental area nucleus accumbens circuit of the mouse brain.

18:39That was going to be my guess, but, you know. Yeah. So I was interested in drugs that primarily targeted dopaminergic systems. And what were you looking for? I was interested in chronic high-dose administration of methylphenidate, which is Ritalin. You know, humans, we give people Ritalin starting at very young ages. So I was very interested in what chronic exposure to these drugs means for the brain as you get older. Does it make you more or less susceptible to drug addiction? And what'd you learn? It's tough to say. I did show that in some animals you get tolerance to other drugs that are similar.

19:24In some you get sensitization, so they're more sensitive to the effects. You also get transferal, so different drugs that don't necessarily primarily hit that pathway will begin to hit that pathway. I've read that the mouse or rat model in research can be really fruitful for certain kinds of research, but unfruitful for others. What can you tell me about that? I can say that, for example, in the area where I was looking, which is a group of structures that we call the basal ganglia, there's a lot of similarity between basal ganglias across all mammals, heck, across like reptiles. It's when you get into kind of higher order stuff that things get more different.

20:06Certainly there are drastic differences in things like the immune system. But I do strongly feel that rats and mice are really essential to our understanding of the human body and the human brain. What are the other things that make mice and rats still really popular subjects of this kind of research? Is it that they're available, cheap, docile, that they breed quickly, that they respond quickly? Mice and rats have become very popular research animals, in part because they were actually sold that way. C.C. Little, who founded the Jackson Laboratory in Maine, which is one of the world's biggest purveyors of mice for scientific purposes, he wrote a piece in Scientific American selling the mouse as a lab animal to the public.

20:54The opening line was, do you like mice? Of course you don't. He basically said mice are awful and we hate them, but they could be heroes of medicine. It can be a replacement for other animals that we are currently using. At that time, dogs were a really big research animal. He proposed mice as being, you know, cheaper, faster. They do have all of those things. We have amazing abilities to alter their genetics now. But all of that stems from the fact that we consider them pests. We consider them expendable. And how do you feel about that as a human? It's complicated. Says the woman who, as a scientist, did her share of rat and mouse experiments.

21:42Sure did. And I'm guessing a bunch of them died in the process of that, yes? Yes. Hundreds. And I feel bad about it. At the same time, you know, they worked really hard for me. They worked hard for me. I liked working with them. Rats are much sweeter than mice, by the way. If you're going to have one as a pet, have a rat. Mice I like because mice are honest. Mice don't like you. They're never going to like you. Rats like you. You pick one up and after a while they snuggle into you. They'll like snuggle in your armpit or your elbow or they'll get on your neck. They're sweet and they're smart. They make great pets, honestly.

22:22Okay, for the record, I'm looking here at your author photo where you're looking like a regular human, right? Dressed nicely, standing in a nice place. But then you've got this rat kind of curled, not even curled up, like luxuriating in the crook of your arm. Yeah, that's Magrat is her name. And she is not mine. And sadly, she has since passed away because rats don't live very long. But she was a wonderful model. She did not pee on me the entire time. I was shocked. This kind of affection toward the rat, expressed here by Brookshire and earlier by Julia Zichello, would seem to be rare. Anti-rat sentiment is widespread and it is vocal.

23:06Let's not forget, New York Mayor Eric Adams calls rats public enemy number one. But there are other voices out there and other sentiments. A researcher at Utrecht University in the Netherlands named Kuhn Bomer published a paper called Catching the Rat in which he examines the portrayal of rats in 20th century novels, movies, comics and more. In this analysis, Bomer found an extraordinarily diverse spectrum of human rat relations. He argues that for many people, rats are no longer seen chiefly as villains. And here's Bethany Brookshire again. I absolutely think the way we see animals in media can strongly affect our perception.

23:49I've been able to learn from my own research that rats are absolutely not public enemy number one everywhere. You may remember the story that Brookshire told us in part one of this series about the temple in India where rats are worshipped. They don't have to be the villain that we see them as. They could be something else. and the good news is that humans can change their minds. We do it all the time, so we could do it with rats too. I love the movie Ratatouille. I love that movie because not only do I like rats, I love food. I've never yet been able to make that picture-perfect Ratatouille that Remy makes.

24:31It never looks that good. Coming up, we go back to Jan Pinkova to find out the real mission of the film Ratatouille. Really to help us get along with each other. I'm Stephen Dubner. This is Freakonomics Radio. We'll be right back.