Animals are Evolving to Cope With City Life

You may think humans are changing to adapt to city life. However, animals living in cities are evolving faster. Metabolisms of the little creatures are running hot. In Puerto Rico, anole lizards can travel across concrete due to changes in their feet structure.

Animal in city

Charles Darwin did get things wrong. Evolution does not just happen over tens of thousands of years. It is dynamic. Alterations are rapid. PCB (Polychlorinated Biphenyls) levels rise in cities and it will kill some animals. The mummichog fish has quickly evolved to survive the poisonous chemical.

The shorter the lifespan of living organisms the faster they evolve. A long-time resident of cities is the European blackbird. It has developed more practical beaks and songs. Moreover, their digestive system can digest food scraps discarded by people. Urban blackbirds no longer migrate.

Mosquitoes in the London Underground have changed dramatically. They breed one-on-one, not in the clouds of mozzies in a sexual frenzy like their forebears. No blood meal is required before eggs are laid. Different rail lines have their own types of mosquito.

Coyotes wander the streets of Chicago, going to rooftops to raise their young. New York mice no longer succumb to fatty foods thrown away by humans. Because people are kept alive by modern medicine we hardly evolve at all. Eating take away food does not kill us before the age of procreation.
Urban Darwinism: Species Evolving to Survive Cities. In urban areas, forces rapid natural selection leading striking genetic changes animals. Dutch biologist Menno Schilthuizen talks Yale e360 transformations seen creatures ranging mice Central Park anole lizards Puerto Rico. The unprecedented influence humans exerting natural world given epoch Anthropocene. Now, his latest book, Darwin Comes To Town, evolutionary biologist Menno Schilthuizen explores influence rapidly reaching genes plants animals.

In interview Yale Environment 360, Schilthuizen, researcher Naturalis Biodiversity Center Netherlands professor Leiden University, describes how, fast-paced natural selection, creatures cities suburbs genetically evolving deal omnipresence humans. Examples abound. Urban populations birds, adjusting traffic noise, becoming hard-wired sing higher pitch their country cousins. White-footed mice Central Park evolving better deal fatty foods New Yorkers serendipitously drop their way. Caribbean lizards undergoing genetically driven physical changes they better maneuver urban surfaces far smoother rough bark trees.

Schilthuizen discusses theories challenge current conservation orthodoxy, noting, example, corridors enable isolated wildlife populations connect may not always advantageous urban setting “local adaptation deal specific local conditions something that’s important animals.” Still, says Schilthuizen, ability species adapt city life way lessens urgency preserve earth’s remaining natural areas. “You appreciate what’s going evolution artificial human-constructed environments cities,” he says. “[But] someone inspired biodiversity, me would tragedy lose species need untouched areas survive.” Yale Environment 360: You write fascinating examples species have rapidly changed urban environment, including American cliff swallows, se wings have become shorter they take off faster vertically face oncoming cars. And then there’s case white-footed mice New York City, live isolated populations various parks. What’s genetically different populations, pressure diverge way?


Menno Schilthuizen: This work that’s been done Jason Munshi-South Fordham University. He found number genes different several parks he looked at. And they ly seem have diet, but bit pollution disease resistance. In Central Park, he found mice there had two genes seem have evolved different direction compared isolated mouse populations city, genes have resistance aflatoxin, harmful compound formed nuts get infected particular type fungus grows discarded peanuts, example, toxic many mammals, including ourselves. And second gene has [accommodating] fatty diets. Central Park far visited park he looked at. Twenty five million visitors go there every year course they leave junk food, discarded nuts, muesli bars, what-have-you. And presumably mice there get substantial portion their nutrition human-derived foods, fattier may have aflatoxins them. “The idea it’s always good connect populations corridors maybe not always true local evolution… [is] important animals.”

You give examples plants animals have adapted natural selection traffic noise, road salt, heavy metals, city lights. And then there’s case foot pads Puerto Rican crested anole lizard. Tell me example urban-induced genetic change. Schilthuizen: Anole lizards really poster boys evolution first place. They’ve diversified hundreds species Caribbean, normally natural conditions. There’s species lives Puerto Rico, both forest cities. In forest, particular species anole lizard runs branches catches insects, but city ly hangs around human structures, walls windows, large often much smoother surfaces forest. And lizards need grip their substrate quite tightly. They’re heavy enough break bones they fall great height. So they have toe pads, geckos do, lamellae help them grip surfaces. But sometimes they fall, that’s course evolution comes from, animals die falls, animals cannot move fast enough surface get way predator get prey themselves.

And we see cities, legs have become longer they have obtained more lamellae their feet. And idea surfaces city smoother they need better grip. Also, surfaces usually much larger flatter branches forest, lizards need longer appendages move faster hold better. There nice videos you see forest lizards, you put them tiled, slippery urban slope, they really have trouble walking properly, city lizard runs it’s problem all. Kristin Winchell [a post-doctoral research associate Washington University] researcher working this. A comparison Puerto Rican anole lizard forest (left) adapted live urban environment (right) navigate painted concrete surface, tilted 60-degree angle. A comparison Puerto Rican anole lizard forest (left) adapted live urban environment (right) navigate painted concrete surface, tilted 60-degree angle. A comparison Puerto Rican anole lizard forest adapted live urban environment (right) navigate painted concrete surface, tilted 60-degree angle. Videos courtesy Kristin Winchell

And she did study urban forest lizards were raised same way saw true genetic change. Schilthuizen: That’s crucial type experiment many researchers working — so-called common garden experiments, you get eggs young animals two different habitats, city forest, you bring them lab same conditions, you still see differences then clearly it’s evolution genetic Habitat Edges: Making room wildlife urbanized world. Read more. Counter notion fragmentation threatens wildlife, there’s now theory urban fragmentation may actually help certain urban populations. I’m thinking particular bobcats Southern California you wrote about.

Schilthuizen:bobcat population partly urban population Los Angeles, they actually process really invading human-dominated areas. They cross gardens streets quite easily, but they cannot cross really big highways. In area, two major highways bisect region basically four sections bobcats live, but they cannot easily cross section other. Research wildlife zoologist Laurel Serieys found you see pattern four sections genes bobcats. These genetic markers different each section, suggesting they mix lot every section, but they rarely cross highway, four sections basically evolve independently.

In particular section there mange epidemic, disease caused spread mites burrow skin big cats, often exacerbated pesticides bobcats accidentally ingest makes their immune systems weaker. And seems many bobcats died disease past -and-a-half decades, surviving were had genes particularly good affording resistance particular disease. And it’s not certain same would have happened four sections bobcats would have been touch each other, then population needed resistance may have been swamped genes coming s, similar have prevented white-footed mice New York adapting their local conditions.

So idea it’s always good connect populations corridors maybe not always true local adaptation, local evolution deal specific local conditions something that’s important animals. “If we want make cities greener, then best candidates would species have already adapted urban conditions.” Urban environments even having effect mating. In 1980s, few dark-eyed juncos, then had bred mountain forests, began stay year-round San Diego, California. It discovered female urban birds preferred males few white feathers their tails, their forest counterparts looked guys lots white feathers. What’s going there?

Schilthuizen: So competing territory mountain forests they normally live, it’s important have bright, white colors tail dark feathers head, striking s aggressive successful defending territory. And territories mountains extremely important season there insects short. And you need defend territory males female raise least clutch eggs few insects there are. But San Diego, sea level, it’s urban environment there’s plenty food they start breeding early year. They easily have three four nests year, importance maintaining territory not great anymore. And females, it’s actually much more important male helps raising young rather fighting males. So you see colors males changing, preference females changing. So city, white tail disappearing darkness head becoming less striking, presumably important defending forest territories, city not crucial more.

So you need kinder, gentler males city? Schilthuizen: Exactly, sort metrosexual juncos. A bobcat photographed camera trap Los Angeles' Griffith Park. A bobcat photographed camera trap Los Angeles' Griffith Park. National Park Service. You have interesting thoughts regarding non-native species urban environments. You say green urban architecture must accept many plant species have successfully evolved adapted urban environment not native, plants green urban planners should using.

Schilthuizen: To begin with, urban environments melting pots anyway. In cities, main players ecosystem species have been brought people, not necessarily native species, smooth running urban ecosystem best species may not native species. And more importantly, I think, we want make cities greener, then best candidates would species have already adapted urban conditions rather species you pick catalog garden center. It’s best get species have already experienced long period adapting urban conditions, species you find growing vacant lots city. And you’ll find many fact exotic therefore probably species best suited growing green roofs green walls green you want design city.

You’re quite adamant, though, take-home message book should not misconstrued be, “Hey, everything okay nature adapting increasingly urban world.” In Defense Biodiversity: Why protecting species extinction matters. Read more. Schilthuizen: I think it’s fascinating process study adaptation wild species human-created conditions, you see fascinating examples rapid evolutionary adaptation there. But it’s important realize flip side fast evolution lot death. To able evolve fast you have have great difference individuals make individuals don’t. So we see evolving few species were lucky enough have variants were able live artificial conditions we threw them. Behind probably much larger group species were not able adapt change environment we create. So it’s certainly not true species adapt, we don’t see species didn’t adapt. They simply disappeared. They extinct. And they survive areas probably pristine.

As biologist somebody ’s inspired diversity, me would tragedy lose species need untouched areas survive. So preserving bulk earth’s biodiversity we still need protect untouched areas. Meanwhile, you appreciate what’s going evolution artificial human-constructed environments cities. “My vision have monitoring system urban evolution we citizen science constantly watch process taking place.” You discuss citizen scientists book, you have idea you propose called “urban Evo Scope.” What would entail?

Schilthuizen: It would simply entail people cities observing, especially photographing otherwise documenting, appearances urban animals plants. In Holland, we’re running pilot project mapping urban evolution citizen science, people photograph particular species land snail, grove snail, comes many different shell colors. And we have evidence — we’re testing citizen science — shells cities lighter shells outside cities urban heat island, creates higher temperature cities, lighter shell protected overheating lighter shell color reflects heat better darker shell colors. So we had 10,000 snails photographed citizen scientists, upload them website. We still need work human validators check photos, but artificial intelligence soon should possible image analysis image recognition automatically. And then we roll many urban species animals plants.

My vision have sort automatic monitoring system urban evolution we general public constantly watch process taking place, even discover urban evolution species we didn’t even know were evolving. And it’s way general public really begin understand process evolution begin appreciate it’s something you watch even backyard.
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