Science Friday - Are Raccoons On The Road To Domestication?

Episode Date: January 8, 2026

What does it mean to be a wild animal in a world dominated by humans? A recent study found that city-dwelling raccoons’ snouts are getting shorter—a sign of domestication. Another study on dark-eyed juncos living on a Los Angeles college campus found that their beaks changed shape during the COVID-19 lockdown, when there wasn’t as much food and trash on campus.  Evolutionary biologist Pamela Yeh and animal domestication expert Raffaela Lesch join Host Flora Lichtman to discuss how wildlife is evolving in urban areas, what it means to be domesticated, and when we can expect to have a pet raccoon sleeping at the foot of the bed.  Guests:Dr. Pamela Yeh is a professor of ecology and evolutionary biology at UCLA.Dr. Raffaela Lesch is an assistant professor of biology at the University of Arkansas at Little Rock.Transcripts for each episode are available within 1-3 days at sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

I'm Florida Lichten, and you're listening to Science Friday. First, there was Pizza Rat, then Central Parks, celebrity, coyote. And finally, I give to you drunk raccoon. A now infamous raccoon. Video obtained by NBC News shows the critter inside of Virginia liquor store. A trashed panda spayed out next to a trash can and toilet, like that one person that maybe had one too many at the holiday party. And there might be more to this ridiculous story. then amazing memes. This raccoon points with its tiny little adorable hands to a possible larger

trend. A new study shows that raccoons are showing signs of being domesticated. Today we are talking about that and what it means to be a wild animal in a world dominated by one animal in particular us. Here to discuss are Raphael Aleish, a biologist studying raccoons at the University of Arkansas at Little Rock, and Pam Yeh, an evolutionary biologist studying. birds, among other creatures at UCLA. Welcome to you both to Science Friday. Hi. Thank you for having us. Yeah, thank you so much.

Raphael, let's start with that raccoon that lived its best life in the Virginia liquor store. Yeah. When you saw that story as someone who studies raccoon domestication, what did you think? So I actually got an email. A news agency was asking me for comment on that. And it's like, I'm not sure what to say other than I'm pretty sure it was. fairly drunk. But yeah, that

was honestly perfect timing for our study. It almost seemed like we paid off that raccoon to like break into a liquor store right after our paper came out. Yeah. I mean, okay, so what are the signs that what are the signs that raccoons are getting

domesticated? Yeah, so I got to preface this by saying that there's like basically found one trait that could be associated with a domestication phenotype. We can't clearly say that they really are on the pathway to domestication, but we can kind of use that as an indication of them potentially being on the pathway of domestication. So what we found was that urban raccoons have shorter snouts than raccoons that live in the countryside. And this reduction

in snout length is a trait that we very commonly see in domesticated animals. And it's part of what we call the domestication syndrome. So a whole collection of traits that we very much associate with an animal being domesticated, like floppy ears, curly tails, white patches, smaller brains and shorter snouts. Smaller brains? Yeah. Yeah. Which it doesn't automatically mean that they're dumber because there was a study we published

on on cat brains and domesticated cats have smaller brains and wild cats. And I had... Yeah, watch out. We have like really a lot of team cat people. Yeah, yeah, yeah, exactly. So I was just wanting to say like we never said domesticated cats are dumber because it was just about pure brain volume. It doesn't have to mean anything in regards to intelligence necessarily.

But yeah, all of those things are traits we associate with domesticated animals. But why does snout size? Why should that correlate with whether an animal is domesticated? So there's one hypothesis, and I'm going to walk you through this hypothesis, but keep in mind we're still arguing whether this is the thing or not, whether it's like true or not. But the main thought that we have is all these traits that we see into domestication syndrome potentially could be explained by a mechanistic pathway in the early development. So if you think about the journey of a domesticated animal,

at the very beginning stages they have to adapt to living in close proximity to humans. So they undergo a fairly strong selection pressure for friendly and tolerant behavior, because usually animals, when they live close to us, you know, if you're too aggressive, then you usually get eliminated from the breeding population. So animals that are tolerant and can make best use of that human environment can reproduce more. So over time, you have this what we call selection pressure for tameness. And this hypothesis, the neural crest domestication syndrome hypothesis suggests that the selection for tameness alters the migration and proliferation of neural crest cells.

Those are cells that are very important in development and provide a lot of ancestral cells for different organ system. So that has the potential to explain all of these traits that we observe across the phylogenetic tree of domesticated animals. Wait, let me see if I understand. So if you start behaving tamely, somehow that is linked to an embryonic development stage that also changes the size of your nose. So it's kind of, it's really like a, think about it as like a multi-generation thing. So that's not something that happens super fast, but would be a very slow process where basically over many generations, these traits basically get reinforced and then show up as this domestication syndrome. Pam, how do we define domestication? Oh, that's a good question. You know, we have

these wild animals and their closeness with humans in terms of their proximity starts to change their behaviors, change their morphology, change their genes, because their selection for the one that once it happened to be tamer, the ones that happen to have the traits that humans find appealing or find useful. Raffaella, you might have a better. I was really interested to hear your take on it because the definition of domestication is like, that's actually a really, really difficult question. There's a bunch of new research that came out where we basically argue back and forth, and that's kind of like the fun, the sweet spell of science, right? when you have these back and forth arguments of what is domestication, how do you define it?

Because of course you have the aspects of us like selecting, like actively selecting and breeding, but then you also have aspects of really like these very beginning stages where animals like get used to human environment. And that doesn't necessarily have to end up in a domesticated product. And I think there's kind of like more of a spectrum really of like where do animals end up on that spectrum. But yeah, the definition is actually really kind of tricky. And just in the last 12 months, there have been a bunch of papers that came out arguing back and forth on how we define these things. Because some definitions, for example, would consider, I think, bedbugs to be domesticated. And I hope I remember it's correctly, but how sparrows to not be domesticated.

So it is really tricky to find a definition that encompasses this kind of fairly complex interaction and, and set up of what it means to live in close proximity to humans. Pam, you had a recent study on the songbird, the dark-eyed junco. So introduce us to them and what their life is like in terms of the ones that you study. Yeah. So the dark-eyed junco is a small passerine. It's an unshrieked sparrow. And they typically, they're found actually in many places in the U.S.

So they're a very common species. but they're typically found at altitude in the mountains in forest habitat. About maybe 50 years or so, they colonized an urban area in Southern California, which is the campus of UC San Diego. And so it's been almost 30 years now since I started studying those guys as a graduate student. And, you know, because they were here. And my advisor said, you know, there's something interesting going on. You're going to find interesting evolution because this is such a

different environment, you know, or we should at least look, you know, and from where they live in the wild. From where they live in the wild. They're very, very different. And of course, you know, when you get into this type of field, you want to go out to, you know, you want to go to the Himalayas, you want to go to Antarctica, you want to go far away. And I was not excited at first about this. But they have turned out to be such an interesting species and an amazing set of populations. and they have colonized San Diego, but then they've colonized other Southern California urban areas over the last few decades. And so now we have multiple, as far as we can tell, fairly separate urban populations with minimal gene flow. And so that allows us to ask some questions about generalizations we can make about urban evolution. Like are each of these populations evolving in the same way?

Are they evolving in different ways? what are the important selection pressures. Okay, so you studied these birds during the lockdown. What did you find? We found that the birds that were born in the years where we didn't have a lot of people on campus actually had longer, skinnier beaks than the ones that were either born before the pandemic or born, you know, 22, 23, 24 afterwards. It turned out that the ones that were born during the ones that were born during the ones that were born

during the 2020 and 2021 campus closures, had beaks that looked more like the wildland beaks that were longer and skinnier, more slender. Why would that be? That is a very good question. And we think it has to do with the food on campus. We have a lot of students on campus, people, faculty, staff, and so everyone is eating, and there's trash, you know,

overflowing in the trash hands sometimes. And, you know, we leave. leaf crumbs everywhere. And I think that there was strong selection pressure during normal times. For birds that had shorter beaks, they probably were able to get at more of that food. Short beaks are good for trash. We think so. I think that they're good for a kind of a generalist being able to grab at the food that we produce. We don't know for sure. So I think that would be like an important thing to test. But that seems to be the case that they can handle more. more of the odd-sized and variable-shaped food a little bit more easily.

Whereas during the pandemic, when there was way less food on campus, birds were, junkers are typically granobores. They eat a lot of seeds. They feed their offspring insects. And so you often see them digging in lawns and vegetation looking for insects or, you know, getting the seeds. And we think that those long slender beaks do better with insects and grains. Pam, can I ask you a question?

Sorry, Flora, I don't want to interrupt, but this is super interesting. Do you think that this could also be like a plastic response to what the birds are exposed to early on? Yeah, that's a good question. And so that's why we have to be a little hesitant when we say rapid evolution, you know, rapid evolution, you know, as a result of the pandemic. Because it could be a plastic trait. It could be. When you say a plastic trait, you mean that it's basically a trait that is adaptable based on the the environment that they're in.

Exactly. It can change during their life. Exactly. Exactly. And so we can't fully rule that out. But we know in general for birds, there are beaks, there are genes that are related to all these beak traits. And so we think that this is one of those things that doesn't change that much. But I think it's something we probably need to, it would be nice to look into more.

Don't go away because when we come back, Raphael, I want to hear when I can expect to have a pet raccoon. Sounds good. And whether I can look forward to a raccoon doodle, a raccoon frieze, an English cockercoon. I love it. We're back. I'm talking with biologist Raphael A Laish and Pamela Yeh about urban wildlife and how these creatures are becoming a little less wild. So, Raphael, we know with dog domestication that, you know, phase one with wolves was, sort of wolves eating our scraps. And I guess, you know, these days a lot of animals are living

beside us, rats, bears, possums. Is there something else about an animal that makes it prone to domestication? Yeah. So you're asking all the big questions, which like is really good. So we have some thoughts on what might kind of like increase the probability of like, like an animal falling down that hole of like the domestication pathway. So they have to have a social system that kind of has enough complexity in it that would kind of like benefit a coexistence between these animals and us. Also the animals have to be animals that are not super dangerous to us humans. So bears, for example, would most likely never end up on the pathway to domestication

simply because they are too dangerous to really create this environment of like, you know, a human environment and all of that. So there's certain limitations. But wolves were dangerous to us, right? Well, I mean, they're kind of, like, usually they, like, wild wolves are really kind of like, they try to stay away from humans. So they're really, I guess they could be dangerous if you, you know, if you really push the wolf to its limits, but they're not really out to, like, get humans. That's not really... Eat us.

Yeah, exactly. Yeah, we're not on the menu. Of course, like nutrition, dietary background could make a huge difference. One thought, for example, that we had is that animals that are able to exploit the human trash that we have laying around, because they have somewhat of a match with their dietary background, would have an easier time being domesticated. So if we look at dogs, for example, they have the ability to digest starch a lot more. than wolves do. So they clearly adapted to kind of like going throughout trash and, you know, eating whatever bread and carbohydrates we throw away. So animals that are able to kind of thrive on

what we throw away potentially have an easier time going down that pathway. But now if you think about cats, they don't really do carbohydrates to the same degree that like dogs can. There you have argument that the trash that we have attracts rodents. So cats might have kind of like exploited the rodents on the trash. So we were thinking that or the initial thought behind looking at raccoons was, well, we know they're there. We know that every single trash can or every single dumpstone campus houses raccoons. So it was kind of interesting to look and see if there was a pattern that would hold across the entirety of the United States. Rafael, how long till I have a raccoon sleeping at the foot of my bed. Oh yeah, and see, this is where the bad news comes in. I'm so sorry.

I wish time travel was a thing because it definitely would not be in a human lifetime. So if they are in the pathway to domestication, it would most likely be similar to other animals like thousands of years, so many, many generations before we end up with like a version of this animal that could be considered domesticated. And there's also another thought that we have where we kind of want to confirm our finding, and that is, because it ties in so nicely with what Pam said earlier, about, like, dietary impacts on, like, morphology and anatomy. So we just looked at this change in snout from, like, a perspective of a domestication framework. But we also need to consider that potentially there could be a difference in dietary background in all of these

populations, and we have to test out and rule out that that's not a signal that we're picking up. I don't think it is, but, you know, that's the joy of science. It doesn't matter what I think. We're going to need data for that. This is a tiny bit philosophical, but do you both have feelings about wild animals becoming more dependent on people? Yeah, I think sometimes people think about humans as one thing, and then there's nature and there's us, but we're really very much a part of the ecosystem.

And the animals affect us and we affect other animals. So, you know, we really need to be aware of we want to think about how we want to change things or how we are trying not to change things. The fact that our cities keep encroaching, we keep encroaching into wildlife and kind of like true wild environments. If we do that, it's almost inevitable that animals will adapt to us. Like at the end, we're also like ecosystem engineers, right? So wherever we go, we change things. And I think that has to be a very conscious thing that we have to consider as humans. How do we deal with that?

Pam, Raphaelah, thank you so much for talking to me today. Thank you. Thank you so much. Thanks for having us. Raphael Lash is an assistant professor of biology at the University of Arkansas, Little Rock, and Pam Yeh is a professor of ecology and evolutionary biology at UCLA. This episode was produced by Kathleen Davis and D. Peter Schmidt. Thank you for listening.

And if you have an urban wildlife encounter that you want to share, or tell me what wild animal is on your domestication wish list. I'd love to hear from you. 877 for SciFri. I'm Flora Lichtman. See you next time.