07/27/2018

Adapt Or Die In The Urban Jungle

30:18 minutes

raccoon sleeping on air conditioner outside
A city raccoon rests on an air conditioner unit. Credit: Shutterstock

If you thought city life was stressful, imagine being a wild animal trying to outlive speeding cars, toxic chemicals and heavy metals, or even the unnaturally bright nights and din of traffic. Why stick around at all? Yet our urban areas still teem with wildlife. Pigeons, mice, lizards, moths, and plants all eke out their livelihoods in sidewalk cracks, subway tunnels, and building ledges (like the raccoon that napped on a skyscraper in Minnesota, as a dramatic example). But how is city living affecting how these organisms evolve?

[The eerie glow of blue ghost fireflies.]

Biologists asking this question are coming back with answers from urban areas all over the world—observing sexual selection gone awry, catfish learning to eat pigeons, an emerging new species of blackbird, birds singing louder and in a higher pitch, lizards with stickier feet, and toxin-tolerant flowers. Even Darwin’s famous finches seem to be evolving in response to human activity in the Galapagos.

Evolutionary biologist Menno Schilthuizen, author of Darwin Comes to Town, tells tales from the front lines of urban evolution research. Read an excerpt of the book here.


Calling all word nerds! Sign up for Science Diction, a weekly email about words, science, and language.

Segment Guests

Menno Schilthuizen

Menno Schilthuizen is an evolutionary biologist at the Naturalis Biodiversity Center, and author of Darwin Comes To Town: How The Urban Jungle Drives Evolution (Picador, 2018). He’s based in Leiden, Netherlands.

Christie Taylor

Christie Taylor is an associate producer for Science Friday. Her day involves diligent research, too many phone calls for an introvert, and asking scientists if they happen to have an audio recording of their research findings.

Elizabeth Carlen

Elizabeth Carlen is a PhD candidate in biology at Fordham University in New York, New York.

Segment Transcript

JOHN DANKOSKY: This is Science Friday. I’m John Dankosky. City life can be hectic. Your neighborhood is crowded, and there’s constant noise from traffic, sirens, or early morning garbage trucks. Public transit doesn’t always work, and the summer breeze– not exactly refreshing right now.

But if you find urban living tough, try being a mouse or a lizard, or even a flower trying to start a new generation in a crack in the asphalt. Your hazards include speeding cars, marauding cats, and water tainted by car exhaust, road salt, and who knows what. It sounds tough, right?

Well, it could be the perfect laboratory for natural selection. That’s what my next guest is here to talk about. As human cities continue to grow around the globe, a new wave of evolutionary biologists is looking at how our neighbors– the feathered, the furry, the photosynthesizing– are learning to thrive.

Are we even influencing the creation of new species? Menno Schilthuizen is evolutionary biologist for the Naturalis Biodiversity Center in Leiden, Netherlands. He’s also the author of Darwin Comes to Town– How the Urban Jungle Drives Evolution.

So what’s your favorite urban wildlife? Give us a call. Our number is 844-724-8255. That’s 844-SCI-TALK. Or you can tweet us @scifri. Menno, welcome to Science Friday. Thanks so much for joining us.

MENNO SCHILTHUIZEN: Thanks for having me.

JOHN DANKOSKY: So a lot of us might not feel like we’re surrounded by wildlife when we step out the door, so why don’t you paint a picture of what you see as the typical urban ecosystem?

MENNO SCHILTHUIZEN: Well, yeah, of course there are some very obvious, very large animals in cities that we know. Here in Europe, we’ve got foxes. And in the US, you’ve got coyotes. Lots of birds, like peregrine falcons, swifts, your average duck in your city pond. But I think the majority of biodiversity in the city is actually much smaller and less obvious– things like little weeds, and little insects and snails that are finding tiny, tiny niches in forgotten corners of the city. And there’s actually much more biodiversity in cities than we think.

JOHN DANKOSKY: Yeah, that’s the remarkable part. We think about the natural world being something outside the city, but you write about this teeming life that’s all around us that we probably just don’t notice because it’s right underneath our noses.

MENNO SCHILTHUIZEN: Yeah, a lot of it we don’t notice unless we start looking for it. And actually, you need very little space to look for it as long as you don’t expect very large animals that you would normally find in wild nature. But smaller things– insects and snails and smaller plants and millipedes and wood lice and spiders– they’re everywhere.

I mean, probably in your basement, on your walls, in your carpets. Outside, if you have a little yard, just pick up a stone or look behind a bush and you’ll find species. Some of which are identical to the ones you would find outside of the city, but there’s also lots of species of animals and plants that are really specialized in living in a city in an urban environment.

JOHN DANKOSKY: So we mentioned, already, the hazards from cars and other urban toxins, but what are some forces that might shape natural selection in cities?

MENNO SCHILTHUIZEN: Yeah, cities are really– despite the fact that there’s a lot of biodiversity in cities, they’re also very extreme environment. They’re just as extreme as a desert or a hot spring. There’s lots of dangers, lots of challenges, lots of very unusual circumstances in cities.

So for example, you’ve got the urban heat islands. In cities– well, actually, in Leiden where I live at the moment, it’s very, very hot. And that’s partly even exacerbated by the fact that it’s a large city and you’ve got all this concrete that’s absorbing heat and reflecting it. There’s people producing heat. So in big cities, it can be up to 10 degrees centigrade hotter than outside. So that’s one aspect.

Another aspect is that there’s all these dangers– like pets, for example. The density of predators in the city, where you have a lot of cats and dogs running around, roaming free– that’s a much denser predator population than you would normally find in an environment. Other things are traffic, which kills off a lot of animals and plants and makes it much harder for weeds to germinate in between the cracks of the pavement, and so on and so forth.

So cities offer a lot of opportunities, because there is food. People concentrate a lot of food in cities. So for animals and also for plants, there are lots of opportunities. But there are also many dangers which are very different from non-urban environments, and that causes a very different kind of natural selection in cities than animals and plants are used to.

JOHN DANKOSKY: You write this amazing story about blue tits in Europe learning how to get cream from milk bottles, and they plagued milk men for decades. And in different cities, they seem to learn this independently of one another. And this really gets to the heart of what’s in your book, here– trying to figure out if this is evolution over time or just a behavioral change– some learned behavior– by these animals.

MENNO SCHILTHUIZEN: Right. Yeah, there’s a couple of very famous examples of– and very cute examples, also– of birds and mammals learning to manipulate us, basically. They figure out how to get to a certain food source. So the famous example is already from the early 20th century, when blue tits and grey tits– these little songbirds in Britain– learned how to open the caps of milk bottles that the milkmen, at that time, still delivered to people’s door and left them there for a while until the inhabitants of the house would pick them up.

And these birds would rush in and peck the lid open and steal some of the cream on the inside of the rim of the bottle. And this behavior– this trick to open these bottles– spreads very quickly through these populations of birds, and it also appeared in different parts of the UK at the same time, more or less.

A similar example is house crows in Japan which have learned to use cars as nutcrackers. They have these walnuts, which they place in front of passing cars, and the cars crack open the walnuts and they get to the flesh inside. And again, this is something that seems to have– this behavior seems to have originated in one place and then spread, but sometimes it also is picked up by other house crows in a completely different place where the crows could not have learned it from each other.

So this in itself is probably not evolution. There’s not a gene for opening milk bottles. But there are genes for personalities of birds, and also mammals. So there are genes which make birds better at problem-solving, less fearful of humans and other large animals, more inquisitive of novel objects. Those are all personality traits which have genes and which are, to some extent, genetic. And those general personalities– they can evolve.

So birds can become better at problem-solving in cities, because the genes for being clever in that way are selected. Whereas in nature, probably, they would not have much of an advantage, because the way you crack open an acorn is always the same. But in cities, every year, you have these new opportunities for birds and mammals and other animals to get to human-generated foods.

JOHN DANKOSKY: So we’re making the birds smarter. We’re giving them harder problems to solve over time.

MENNO SCHILTHUIZEN: Yeah, or new problems. I mean, you’re only smart depending on your context. So in the city, it’s smart to be curious about new objects. In the forest, it’s probably dangerous and not very smart to be curious about new objects, because it usually means something is dangerous if humans place a new object there. But in the city, something new often means something that could provide food in a different way than the animals are used to before. So being inquisitive and trying to figure out what that new thing is and how it works is smart in the city.

JOHN DANKOSKY: A lot of people who took high school biology might remember the peppered moth. This is a classic example you write about of evolution in response to pollution during the Industrial Revolution. The moth, it is told, got darker to hide better on soot-stained surfaces. So is this still the textbook example of a type of adaptation or evolution that you’re talking about in the book?

MENNO SCHILTHUIZEN: It is, actually, yes. It’s a very famous example, and it’s still a very good example of how a change in the environment that’s caused by humans drives the evolution in a wild organism. So just two years ago, it was figured out exactly which bit of DNA is responsible for the color of those wings of those moths.

And it turns out it’s a single switch gene that turns on the melanin– this dark pigment– in the wings of the moths, and there’s just little change in that gene that has caused these moths to become darker– and also to become lighter again. Because in the 1960s, the legislation to remove soot from the air was introduced. So the air got cleaner again, the trees got lighter again, and these moths became lighter again.

So you have a very beautiful seesaw of evolutionary change where the moths first, in the 19th century, became darker and almost completely took over the light moths, and then the reverse happened in the late 20th century. And today, the moths in UK and in Europe look exactly the same way they did before the Industrial Revolution.

So I think it’s still a textbook example except that, of course, it’s a single gene. It’s about the simplest kind of urban evolution that you can think of. It’s a single factor in a single gene that changes these moths. We don’t see a new species appearing. And there are other examples, nowadays, of animals that are changing– are evolving– because of urbanization that involve many genes, and they evolve lots of different parts of the genome, and where you see something that you could really say is the evolution of a new species.

JOHN DANKOSKY: We’re talking with Menno Schilthuizen about his new book, Darwin Comes to Town. But let’s get to a phone call. Jeff is calling from St. Louis, Missouri. Hi, Jeff.

JEFF: Hi, how are you?

JOHN DANKOSKY: Good. What’s on your mind?

JEFF: I’m the lucky guy that gets to band peregrine falcon chicks in St. Louis. We’ve got three pairs– three pairs in downtown St. Louis. And I’ve got males and females– adult males and females– on these territories that have been there for many years now, and I’ve always wondered how they’ve adapted to the glass buildings.

Glass buildings kill millions of birds a year in big cities here in the United States, yet the peregrines seem to have adapted to the city lifestyle, and it is rare for them to hit buildings and be found dead. And I know that these females and males are the same ones because we have auxiliary bands on them, so we can see that the numbers and the letters on these auxiliary bands from quite a distance. So it’s very interesting to me that they’ve adapted and not hit these buildings like most of the other birds do, and many of the other birds do in the city.

JOHN DANKOSKY: Jeff, thanks so much for that. It’s interesting.

MENNO SCHILTHUIZEN: It is very interesting. I think, yeah, you’re right that glass– and also reflecting steel and also lights at night– kill a lot of birds, and also a lot of insects. I mean, the death toll is enormous. We’re talking about billions of birds and gazillions of insects that are dying because of that.

And when you have a lot of death, you also have a lot of natural selection. There’s a very high premium on being able to avoid that cause of death. So in insects, we’re seeing that they’re now beginning to avoid lights, actually, in areas where there’s a lot of artificial light.

We don’t have any evidence yet that birds are doing the same with either lights or glass buildings, but you would expect that that sort of evolution would be going on. And it could very well be that peregrines– and maybe other birds, also– are beginning to get better at recognizing glass buildings. And not because they’re learning, but because maybe their eyes are changing. We don’t have any evidence for it. But it wouldn’t surprise me, because the death toll in some species of birds is enormous.

JOHN DANKOSKY: You talked about the massive deaths from lights in insects, and light pollution is one of the big features of the urban landscape.

MENNO SCHILTHUIZEN: Yeah. That’s, of course, a very pervasive human-generated change in the environment, and it’s very new change. I mean, there’s never been artificial light at night. For some other aspects of the urban environment, you could find parallels in natural conditions. But in nature, the only light at night has always been the moon and the stars. And only less than 200 years ago, suddenly we had all these other lights appearing at night. And all the animals that are active at night and were using the moon to navigate started to get confused because of this artificial light at night.

So insects, for example– they have always used the moon as a beacon to fly in a straight line at night. So if they keep a fixed angle with the moon, they fly in a straight line. But they’ve tried to do the same thing with something that they think is a moon but is actually a street lantern, and they end up going in ever-decreasing circles around that street lantern. And they probably die because of the heat of the light, or they just sit there and waste time that they should be spending feeding or looking for mates.

So I think that this light at night is definitely a very important selection pressure– something that could drive evolution. And the evolution you would expect to happen is that these insects start being less attracted to lights; start losing their tendency to use light at night for navigation. And there is some evidence that insects are actually doing that– that city insects are ignoring light much more than rural insects do.

JOHN DANKOSKY: I’m John Dankosky, and this is Science Friday from WNYC Studios. I want to get to another phone call, quickly, here. Becks is calling from Santa Cruz, California. Hi, there, Becks.

BECKS: Hey, there!

JOHN DANKOSKY: Hi, what’s on your mind?

BECKS: Thanks for having me on.

JOHN DANKOSKY: Of course.

BECKS: I wanted to contribute a couple of my favorite urbanized animals. And here in Santa Cruz, the UC– UC Santa Cruz– is considered a city on the hill. And I like to consider our deer a little subspecies, where they will cross the street in the crosswalks. They will eat grass a few feet from a jackhammer. You can walk just a few feet away from them. Where, I know coming from the mountains, that would be dinner. And they don’t seem to have a fear at all.

We also have this wild turkey we call Hank. And Hank has, I believe, a territorial, protective instinct– particularly against mail delivery. UPS men, the mailman, and, I mean, just cars. He’ll chase, he’ll stop traffic and peck at tires, and sometimes even people. It’s really cute and confusing behavior, and I’ve never seen anywhere else.

JOHN DANKOSKY: Well, thank you so much for those two stories, and I want to ask about both those. Other people are tweeting about deer getting less skittish than they were before. And I’ve heard a lot of stories, Menno, about turkeys taking on really aggressive personalities in urban areas all across America. What do you see there? What do you think is happening?

MENNO SCHILTHUIZEN: Yeah, like I said before, there’s probably some sort of general personality change in many of these animals. And to some extent, of course, there’s more specific things they could simply learn and pass on to each other, but there’s more general personality traits that are evolving if they are genetic. And we noted many behavioral characteristics of mammals and birds are genetic.

So in the case of aggression in turkeys– and in Europe, we often see it with large mute swans, which are in cities, which also seem to become more aggressive and more territorial. Also, tameness– I mean, the caller just described that deer are much tamer in the city. We also see that in birds– that the same species of bird outside of the city would fly off if you get within 40 yards from them, whereas in the city, they stay on the floor until you’re just a few yards away from them.

And those things are repeatable, and you can actually measure them. And you can see that they are genetic changes in these animals. So it seems that, in cities, they evolved the personality that, outside of the city, was very beneficial– namely, being scared of people. In the city, often, people are not as dangerous.

[INTERPOSING VOICES]

JOHN DANKOSKY: It’s actually– yeah, better to be closer to the people. Coming up after the break, more stories from the urban evolution jungle. Plus, how one researcher’s untangling the story of pigeon evolution– that’s right, pigeons in New York and all over the east coast. That’s coming up.

This is Science Friday. I’m John Dankosky. We’re talking with evolutionary biologist Menno Schilthuizen about the evolution of our urban wildlife neighbors– how mice, mosquitoes, and even flowers are responding to the pressures of urban living. But first, ever try to shoo a group of pigeons that crossed your path? Tired of dodging close flyovers of pesky, gray birds?

The urban pigeon may feel like another city nuisance, but there’s a lot they can teach us about how wildlife is adapting to coexisting with us. The science is there– if you can just chase it down. SciFri producer Christie Taylor recently joined a biologist pigeon hunt in New York City, and here’s her story.

CHRISTIE TAYLOR: Elizabeth Carlen would be the first to tell you she has understanding friends.

ELIZABETH CARLEN: They’re quite used to going into my freezer to get ice and seeing blood samples, or a dead bird or a dead mammal.

CHRISTIE TAYLOR: They’ll even text her when they see dead pigeons on the streets of New York City so she can snip off a sample.

ELIZABETH CARLEN: Sometimes it’s the whole foot. Generally, it’s just the toe– or a couple toes.

CHRISTIE TAYLOR: Her car and clothes are constantly covered in feathers, too– and sometimes bird poop. But it’s all part of the job, because Carlen is a biologist who studies evolution– urban evolution– in the common city pigeon. These feral, ubiquitous birds are the descendants of wild, cliff-dwelling doves from Europe and North Africa, and they seem to like living with us. They moved into most major cities around the globe, and that sets up the perfect experiment in adaptation and evolution in harsh, dangerous, sometimes toxic environments.

ELIZABETH CARLEN: We’re starting to realize that animals rapidly evolve– much faster than we thought. And that means that organisms are able to adapt to cities– these very new ecosystems, this new habitat.

CHRISTIE TAYLOR: To look for answers in New York City, step 1 is to get in the car. Carlen meets me in Inwood– the northern tip of Manhattan. Our mission– find and capture some pigeons, and then sample their blood. Our getaway vehicle– Carlen’s silvery-gray Subaru Hatchback. She has a stash of bird seed in the trunk, a full tank of gas, and we’re ready to roll.

[CAR HONKING]

ELIZABETH CARLEN: So mostly what I’m looking for is a lot of pigeons that are close together and that are feeding, and kind of distracted.

CHRISTIE TAYLOR: This is harder than it sounds.

ELIZABETH CARLEN: We have not really seen any big flocks on the ground. They all just flew away as soon as we drove up. We’re just stopped for no reason. I am really not seeing any pigeons. No, that just scared them away. So a guy just walked up and pulled up his cane and totally scared them off.

They’re definitely in the neighborhood. Why are they not here?

CHRISTIE TAYLOR: I never thought it would be this hard to find a pigeon in New York, but we finally look out on the Upper West Side– 20 or 30 gray, brown, and white birds just peck, pecking away at a stash of food someone’s left in a park. We sneak up on them, and Carlen pulls out her secret weapon– a net gun. It looks like a long, black flashlight, but it shoots out a net, capturing as many as 13 pigeons in a shot– on a good day.

[SHOT, FLUTTERING]

The birds scatter– except for a few choice research subjects.

ELIZABETH CARLEN: We got two this time, which is great. We’re going to head back to my car so I don’t get a ticket.

CHRISTIE TAYLOR: We have the birds. Now it’s time to collect the data. Remember Carlen’s bird seed-filled trunk? It’s also a traveling lab, packed with test tubes, bloodletting needles, and brown paper grocery bags– where the birds can wait calmly until it’s their turn to be processed. And in just a matter of minutes, she’s gotten everything we spent the whole morning hunting. She weighs each bird.

ELIZABETH CARLEN: So this guy’s about 410 10 grams.

CHRISTIE TAYLOR: She notes its location and color, gingerly draws a small blood sample from a vein under its wing–

ELIZABETH CARLEN: So then I just slowly insert the needle up against the vein.

CHRISTIE TAYLOR: –and fits a small, lavender identification band around one leg. These blood samples will go in her freezer, along with those cut-off toes from roadkill pigeons. And in the DNA of all those samples, she’s hoping to find clues as to why pigeons thrive in big, busy cities.

Are urban pigeons genetically more tolerant of toxins, noise, or light pollution? Are their genes helping them digest our junk food? How are birds in New York related to birds in Boston or DC? We don’t even know how many are out there, and DNA can help biologists count. Then, the last bird in her hands, Carlen asks me a question.

ELIZABETH CARLEN: Do you want to let him go?

[GASP, LAUGHTER]

CHRISTIE TAYLOR: (EXCITEDLY) Yes.

ELIZABETH CARLEN: Cool.

CHRISTIE TAYLOR: By the way, I’m someone who loves New York’s pigeons. They feel like my neighbors. Seeing them hopping along on the sidewalk in the morning gives me this little burst of dopamine, like we’re all in this crazy city together, rushing to get to the train on time.

So holding this calm little bird in my hands– this is really great– is kind of a dream come true. How are you doing, bird? OK, so–

ELIZABETH CARLEN: OK, so yeah, just open the door, and then open your hands.

CHRISTIE TAYLOR: OK. All right, bird.

[FLUTTERING]

And it just went.

ELIZABETH CARLEN: Just went.

CHRISTIE TAYLOR: It just went. And that’s the gift Carlen wants to give other city dwellers, too. The sense that pigeons– they’re not just a nuisance clogging up the sidewalk, eating our trash, or pooping from building ledges. They’re our nature, our wildlife, and part of our shared urban ecosystem.

So why not take a minute? Look up from the crowded sidewalks and screeching traffic and the weird smell of garbage in the wind, and just watch a few of these graceful birds wheeling about in a bright, blue sky. In New York, I’m Christie Taylor.

JOHN DANKOSKY: And you can see pictures from Christie’s pigeon exploration at scifri.com/pigeons. We’re talking with biologist Menno Schilthuizen, author of Darwin Comes to Town. It’s such an interesting story. What else can you tell us about pigeon evolution, Menno?

MENNO SCHILTHUIZEN: Yeah, John, I think that was really a great report on the city pigeon. I think they’re really wonderful animals. And most people wouldn’t consider pigeons as wonderful animals, but they’re ideal for studying this urban evolution.

So there’s some evidence, now, that the wing shape of city pigeons has changed, but also that their colors are evolving. You may have noticed that in cities, you can have these light gray and dark gray pigeons. And it seems that the larger the city is, the more of these dark gray pigeons you have, and their genes for the color of their wings and their plumage.

So there’s also genes for dark gray pigeons and for light gray pigeons. And it turns out that the ones that have dark gray feathers– they have more melanin. This is dark pigment in their feathers. And melanin also helps them to basically detox their bodies. Melanin binds to heavy metals, lead and zinc– of which there is a lot in cities, because there’s a lot of pollution.

In the past, of course, lead from fuel. Today, a lot of zinc, also, from lampposts and electricity poles. And the animals ingest this accidentally, and it’s dangerous for them. And they can get rid of that zinc by basically incorporating it in their feathers, and then it’s harmless and it’s bound to the melanin. So the dark-feathered pigeons are better at getting rid of these metals from their bodies, and that’s why these dark ones do better and you see more of them in big cities.

JOHN DANKOSKY: I’d like you to quickly, though, tell a story that our pigeon-loving producer Christie might not like so much– a story you tell about France, where catfish are jumping out of the water to eat pigeons.

MENNO SCHILTHUIZEN: Yeah, that’s– of course, much of the things I’ve talked about, and also much of the things I talk about in my book, have to do with the physical and chemical aspects of [INAUDIBLE], and that’s the thing you think of immediately. But there’s also a very interesting biological thing going on in cities in the sense that cities are places where all these species of animals and plants come together that have never met each other.

We introduce animals and plants in cities. They start thriving there, and they start building an ecosystem together with species that come from all over the world– from different parts, from rain forests, from deserts, from cities in Asia, Africa, Europe. And in France, for example, they have introduced– well, the rock pigeons are there, which are generally from southern Europe and from Africa– North Africa. And they’ve introduced catfishes from Eastern Europe for angling– for fishing.

And these catfishes– normally– they’re very large freshwater fishes, and they tend to rustle up clams and worms from muddy river bottoms. But in a city in France– in Albi in southern France– they have figured out that you can actually catch– as a catfish– you can also catch pigeons. These city pigeons are bathing– are preening on the water’s edge of the big river that flows through the city.

And these catfishes sneak up on them like orcas sneaking up on sea lions on a beach, and they grab them by their feet and pull them under and swallow them, which is something that catfishes are not supposed to do. But they have an opportunity in a city, and they take it. And in this sense, they’ve created a new ecological relationship between pigeons and catfishes that wasn’t there before and that could be the start of a new evolutionary process.

JOHN DANKOSKY: Well, you mentioned something earlier that I wanted to loop back to about whether or not, some day, we might see entirely new species that live just in cities.

MENNO SCHILTHUIZEN: Yeah. Of course, we humans have been creating cities not for a very long time yet. So I mean, we’ve started doing it a few thousand years ago, but it’s really taken off only in the past century. So animals and plants that are adapting to cities haven’t had much time to evolve.

What we see now is really the beginning of evolution. So not really completely new species are evolving, but there are one or two examples that seem to go a little bit in towards new species evolving and new species being– organisms that had a lot of different genes in their genome that are evolving.

So blackbirds, for example– the European blackbirds, which have invaded cities– and they were one of the first birds to do that. In the early 19th century, in Rome and in Germany, they started invading cities. And they’ve continued doing that throughout the 20th century. And we now see that these blackbirds have a whole range of genes in which they are different.

They sing at a different pitch. They have differences in their intestines. Their beaks are shorter. They don’t migrate anymore, so they breed much earlier in the year than the forest blackbirds do. Their personalities also have changed, also, in the genetic level.

So we have a whole range of differences between the forest blackbirds– the ancestor of the city blackbird– and the urban blackbird. And you could argue that they are on the way of becoming a separate species– some sort of turdus urbanicus– turdus merula, the scientific name of the first blackbird. Maybe in a few hundred years we could speak of turdus urbanicus, the city blackbird.

JOHN DANKOSKY: I want to end on this– and I think it’s fascinating whenever we think about an animal in what we call the wild outside the city. If we have some sort of impact on it and it starts to decline in number, we wring our hands about what we should do to bring it back or preserve it. How do you think about this within the context of this urban environment in which there’s so many animal and plant species that are living amongst us? How should we prioritize what is important and less important to make sure we preserve?

MENNO SCHILTHUIZEN: Yeah, I think– well, we tend to think in terms of individual species. We tend to think we have to preserve this species or that species. Or this species is doing poorly, so we have to help it. But I think what’s much more important– and we’re starting to see that in conservation, also– that people are focusing more and more on the ecosystem as a whole, rather than the individual species. And of course, in cities, you have very few species that are rare or endangered.

Often, they are common species or invasive species or exotic species which usually don’t have much conservation value, but together, they form a very well-functioning urban ecosystem. And I think that ecosystem itself is something that we should preserve and stimulate, and we can do that by creating cities in which there is space for urban nature, by creating bits of vegetation– small bits, large bits– by sometimes maybe creating corridors between parks, sometimes maybe not creating corridors, planting– let’s say not planting parks with species from a catalog of a garden center, but letting them be colonized by urban plants naturally. In all those sorts of ways, I think you can stimulate that these urban ecosystems will thrive.

JOHN DANKOSKY: Menno Schilthuizen is evolutionary biologist at the Naturalis Biodiversity Center in Leiden, Netherlands. He’s the author of this new book, Darwin Comes to Town– How the Urban Jungle Drives Evolution. Thank you so much for joining us. I really appreciate it.

MENNO SCHILTHUIZEN: Thank you, John.

JOHN DANKOSKY: I’m John Dankosky, and this is Science Friday from WNYC Studios.

Copyright © 2018 Science Friday Initiative. All rights reserved. Science Friday transcripts are produced on a tight deadline by 3Play Media. Fidelity to the original aired/published audio or video file might vary, and text might be updated or amended in the future. For the authoritative record of Science Friday’s programming, please visit the original aired/published recording. For terms of use and more information, visit our policies pages at http://www.sciencefriday.com/about/policies/

Meet the Producer

About Christie Taylor

Christie Taylor is an associate producer for Science Friday. Her day involves diligent research, too many phone calls for an introvert, and asking scientists if they happen to have an audio recording of their research findings.

Explore More