How Ants Make Our Cities Healthier
[Quick shots of New York City scenes—traffic, the Brooklyn Bridge, subway cars, tall buildings.]
JESSICA WARE (Curator, Division of Invertebrate Biology): Cities are one of the only habitats in the world that are growing in size, but we’re just starting to understand how they work as ecosystems.
[A rat pokes its head out of a hole in the sidewalk next to a large garbage bag.]
WARE: When you think about wildlife in the city, it might not be exactly alluring…
[A close-up of ants scurrying in and out of a hole in dirt. In the background, yellow taxis whiz by. Ants crawl over a tree root near the street. Other ants scutter around a Skittles wrapper. A sped-up shot of humans and traffic on a New York City street corner echoes the ants’ movement.]
WARE: But if you start looking on a smaller scale, you realize there are diverse insect societies whose tiny cities mirror the busy human streets surrounding them: ants!
[Extreme close-up of ants busily going in and out of a hole in the ground. In another shot, thousands crawl on a sidewalk curb.]
WARE: These are Tetramorium immigrans—pavement ants. They live in cities all over the world, and they like the same kind of food we do.
[Camera pans across a street scene to land on a piece of fried chicken that someone left on a park bench. Hands pull chips out of a bag on the grass that’s surrounded by food trash.]
WARE: In fact, they love it when we humans drop our crumbs.
[Ants move across a stone wall next to a sidewalk. A street median planted with trees and tulips divides traffic lanes in New York City.]
WARE: Researchers calculated that the ants (and other arthropods) living in just these street medians on Broadway…
[A machine dumps food waste into a towering pile at a sanitation facility.]
WARE: …could eat close to a ton of food waste every year—
[A street vendor squirts ketchup on a hot dog. A discarded bag of potato chips lays on the ground.]
WARE: ...equivalent to 60,000 hot dogs or 600,000 potato chips.
[Ants scurry in and out of a hole. In the background are the discarded chip bag and a city street.]
WARE: And these tiny little ants could be helping us out in big ways—maybe even making our cities healthier places for humans…
[Close-up of a single ant investigating an enormous crumb that dwarfs it in size.]
[Title animation: INSECTARIUM]
[On-screen text: American Museum of Natural History]
[Host Jessica Ware stands in front of an exhibit of live leafcutter ants in the American Museum of Natural History’s Insectarium exhibit.]
DIRECTOR [off-camera]: Hypothetical: you are hit by an incredible shrinking ray.
[On-screen text: Jessica Ware, Ph.D. | Curator, American Museum of Natural History]
WARE: As it happens. It happens to people.
DIRECTOR [off-camera]: It does. You’re shrunk down to the size of an ant in New York City. What are the challenges that you are facing, or that an ant might face?
WARE: Well, I mean, the city- a city like New York City, in theory it’s designed to help humans move places very fast. Right?
[On-screen text: Susan and Peter J. Solomon Family Insectarium | American Museum of Natural History]
WARE: And when you’re moving very fast, you’re often not looking at the ground to see little ants that are scurrying around.
[Low-angle footage of Times Square. In front of the glare of huge, bright ad screens, pedestrians, bikers, scooters, and cars speed past.]
WARE: So, you run the risk of being stepped on, bicycled over, driven over.
[A wand sprayer dispersing insecticide moves across a bed of tulips.]
WARE: There’s of course insecticides that people spray.
[Glaring rays of sunlight bounce off tall glass and metal skyscrapers. Time lapse of a busy intersection, showing hundreds of cars moving by and waves of heat coming off the roadway. An orange haze blankets the cityscape. Steam pours out of a manhole.]
WARE: And the temperature. Sometimes it’s a little bit hotter in cities than maybe what you might be adapted for. Because in cities, you have a lot of buildings and pavement that trap heat, creating these urban heat islands that can be many degrees hotter than nearby areas.
[Ware speaks to camera in the Insectarium.]
WARE: It would be tough to be a city ant.
DIRECTOR [off-camera]: But if you can make it here, you can make it anywhere.
WARE: You know, I’ve heard that’s true.
DIRECTOR [off-camera]: Well, ants have definitely made it to my kitchen. Where else are they hanging out?
WARE: Ants are pretty much everywhere.
[Various ant species in a variety of habitats.]
WARE: So, the rainforest, temperate forest, the beach, the desert. Pretty much anywhere on Earth, there are ants.
[Extreme close-up of a single ant. A dozen ants connect their bodies to make a bridge spanning two leaves. Thousands of ants scurry on a forest floor.]
WARE: In terms of sheer numbers, there’s more ants on the planet than there is almost anything else.
[Ware speaks to camera in the Insectarium.]
WARE: So, for every human on earth, there’s 2.5 million ants. That’s a lot of ants.
[Low angle time lapse of ants moving over a sidewalk. In the background, humans also speed by.]
WARE: If you think about it, we’re really living in their cities.
[Ants in a city habitat. Ants in a rainforest.]
WARE: And that’s because ants play an outsized role wherever they are, whether it’s in a city or a rainforest.
[Hundreds of leafcutter ants carry pieces of dry vegetation across the ground at night. Another group of leafcutters marches along a log in a rainforest carrying pieces of green leaves.]
WARE: Take these leafcutters… They—not mammals or birds—consume the most vegetation in Central and South America.
[Ware indicates leafcutter ants in the Insectarium living ant exhibit, carrying leaves through their enclosure.]
WARE: They don't eat these leaves. They don’t eat this as food. This is actually food for the fungus that they're growing.
[Extreme close-up of leafcutter ants on their fungus garden. The fungus is sponge-like—a bulbous blob with holes.]
WARE: And then they eat the fungus. They're basically farmers.
[Time lapse of a single leafcutter ant chewing off a piece of a leaf and carrying it away.]
WARE: And leafcutter ants are just one kind of ant.
[Ants of various species sporting a variety of forms and colors.]
WARE: There’s 14,000 species of ants. They're all in this one family, Formicidae.
[On-screen text: Formicidae | ants]
[Close-up of ants silhouetted against a light background.]
WARE: And we think there are lots more species out there, just waiting for scientists to give them names.
[Ware speaks to camera in the Insectarium.]
DIRECTOR [off-camera]: Very cool. So why are there so many different kinds of ants?
WARE: Well, I mean, that's always a good question. One thing for sure that we know is that ants, individual ants, are actually quite small.
[Various shots of ants that seem tiny in comparison to their environment.]
WARE: And perhaps them being this kind of fun size, tiny insect size that allows them to occupy lots of different niches in one area.
[An ant drinking water collected in a flower’s petals. An ant draws honeydew liquid from a group of aphids.]
WARE: That means opportunities arise for all kinds of specialists and all kinds of ecological roles.
[Broadway street sign. Ware and another scientist crouch in a Broadway street median, pointing at a crumb in the dirt.]
[On-screen text: Broadway and 73rd Street | New York, New York]
WARE: Oh look look look look. There’s an ant coming! There’s the crumb. You did it!
[Ware and the other scientist, Amy Savage, talk in the median and examine small insects through a hand lens.]
WARE: Remember those ants that eat 60,000 hotdogs a year? Well, Dr. Amy Savage was one of the scientists who calculated that number. She’s also done research to understand just who our ant neighbors are.
[On-screen text: Amy Savage, Ph.D. | Assistant Professor, Rutgers University]
[Savage walks through the median, looking for ants.]
AMY SAVAGE (Assistant Professor, Rutgers University): I had done this research for my Ph.D. in Samoa, out in the middle of the South Pacific. And I thought, why- why am I trying to do this thing where I go far away? And so then, when I did the next research project, I said, “What’s happening under people’s feet?”
[At a busy intersection, dozens of people cross the street while a line of cars waits for the light to turn. Savage continues to work in the median as taxis speed past in the background.]
SAVAGE: I realized that people were a part of the story I was trying to understand about insects. So, I went to the most urban place in America and started looking on Broadway, the ants on Broadway.
[On a street corner near Times Square, a plethora of flashing lights and neon signs advertise theaters and restaurants. On a jumbo screen, an animated graphic shows an ant walking on a thin string and flashes the words ANTS! ANTS! in large letters.]
[JAZZY STING OF MUSIC]
[AMBULANCE SIREN BLARES PAST]
[Ware and Savage dig around in the median dirt.]
WARE: I’ve always been told you should dig around where pigeons have just been. What could happen, right?
[The camera tracks along a street in New York. Paralleling that image, the camera tracks along a park path, converted from an old elevated train line.]
WARE: The city isn’t just one big slab of concrete. Just like there are different neighborhoods, there are different microhabitats—like these street medians.
[Savage and Ware talk while standing in a street median.]
SAVAGE: I got to go into these islands of green, in the middle of a street that’s just surrounded by inhospitable landscape, like pavement and buildings. I started to do some research trying to understand just the diversity in these systems.
[Using a tool that consists of a long rubber tube and a glass vial, Savage looks around the media for ants to collect.]
SAVAGE: We collected all along Broadway and we even collected down in lower Manhattan.
[Close up as Savage lifts a rock and finds traces of ant tunnels underneath. Unearthed ants scurry around in the light.]
SAVAGE: What we were expecting to find was three exotic ants and maybe an occasional native one.
[A graphic illustrating the variety of ant species that Savage’s team found in street medians.]
SAVAGE: And what we found were 24 species of ants in the street medians of Broadway. It was way more diverse than we thought it would be. And it’s really exciting to see what they’re doing.
[Close-ups of pinned ants that are scientific specimens in the research collection of the American Museum of Natural History. Each ant is attached to a number of small tags that name its species and give data about the date and location it was collected.]
[On-screen text: Entomology Department | American Museum of Natural History]
WARE: Amy actually donated many of the ants she collected to become part of the permanent research collection at the Museum.
[Savage and Ware stand in the collection room. The box containing Savage’s specimens is open on a desk next to them.]
SAVAGE: These are really special to me. These were collected right here in New York.
[Savage and Ware stand in the street median.]
WARE: So, Amy, what kind of ants live in New York City?
SAVAGE: Most of them are native ants, in terms of diversity. In terms of the sheer numbers. we got a lot of pavement ants in cities.
[Hundreds of tiny ants swarm over a muffin crumb and scurry through leaf litter on the ground.]
WARE: Pavement ants are originally from Europe, but populations have changed so much as they spread all over the world that they are now a new species. They were almost so common that no one bothered paying attention to them in a scientific sense.
[Savage and Ware speak in the research collection.]
SAVAGE: For the longest time they were known as Tetramorium species E. They didn't have a name.
[Various shots of Tetramorium ants. Hundreds move across the ground.]
WARE: But in 2017, researchers started gathering the data they needed to redefine the species as Tetramorium immigrans.
[Extreme close-up of a pinned ant specimen labeled Prenolepis imparis.]
WARE: One of the native species Amy collected was Prenolepis imparis, the winter ant, which is usually more active in colder weather.
[Extreme close-up of Prenolepis imparis ants in a colony. Dozens of small ants with striped thoraxes surround a much larger, winged ant.]
[Savage and Ware speak in the street median.]
SAVAGE: During the summer they estivate, which is kind of like hibernating. They go to sleep when it’s really hot out. It was one of those species that we were really thinking would struggle in cities. And instead, even in August on hot days, we’re seeing Prenolepis running around in New York City. And so, there’s something really interesting happening with them.
[Time lapse footage of a busy intersection with people and cars speeding by. Various scenes of urban greenspaces, including a cemetery, a sports field, and street medians.]
WARE: There are lots of scientific mysteries to uncover in the patchwork greenspace of pocket parks, cemeteries, soccer fields, medians, and street tree beds scattered throughout our cities. But we already know these spots are vital for both people and ants.
SAVAGE: They end up being really important for the people who live in cities, both psychologically and physiologically. And they’re also important for maintaining this diversity of species that provide ecosystem services.
[Time lapse of an ice cream scoop fallen to the ground, melting, and then being devoured by hundreds of ants.]
WARE: And one ecosystem service that city ants perform is helping to clean up our food waste.
[A single ant carries a comparatively large crumb over a red-and-white checked picnic tablecloth.]
WARE: It’s almost a cliche that ants will invade a picnic—but it may be surprising just how important their sanitation work can be.
[Savage and Ware speak in the research collection.]
SAVAGE: I think people have a good sense that if there’s just food lying on the ground, it’s not a good thing.
[A park sign shows a figure disposing of trash in a container and reads, “Leftover food can attract rats. Use trash cans to help keep this area rat-free.” The camera pushes into the interior of a trash can with food waste inside.]
SAVAGE: But even if people are good and put their food in a trash bin, it still goes to a landfill.
[Drone footage of a large landfill as a bulldozer levels it off.]
[New York, Denver, and Nashville street scenes. An NYC Sanitation worker picks up trash bags from the sidewalk and throws them in the back of a garbage truck.]
WARE: One study found that Americans in three cities—NYC, Denver, and Nashville—throw out an average of 3.5 pounds of food waste per week.
[Food waste travels along a conveyor belt. Wide shot of a landfill with large mounds of trash surmounted by large, methane-venting cylinders, each bearing an orange flag. Venting methane flames.]
WARE: A lot of that ends up in landfills where, as it rots, it emits methane—a significant contributor to the rise in greenhouse gasses.
[A small ant tugs a crumb through the grass.]
SAVAGE: So anything that an urban animal like an ant can do to just process that food at the source is going to be an ecosystem service for everyone because of climate change.
[A starling picks at a piece of fried chicken left on a park bench. Rats nibble on a muffin wrapper. A raccoon rifles through a trash can at night.]
WARE: A bonus is that unlike other city food scavengers, ants aren’t nearly as likely to spread disease to us humans than animals like rats, raccoons, or birds.
[Dozens of ants combine their efforts to carry off a sizable potato chip. Trash piles up on the street. Other ants swarm a large crumb.]
WARE: As the paper Amy co-authored puts it, ants’ contribution to urban waste removal is “modest but notable.”
[Dozens of people sit in a small city park during the day.]
WARE: So, of course, ants alone aren’t going to solve global climate change—that’s still on us humans—but we should give them credit for the role they play in greening our cities.
[Ants travel in a line across a concrete wall.]
WARE: And while ants are changing our cities, we’re also changing their tiny worlds.
[Extreme close-up of ants interacting with one another. Ants swarm a discarded chip.]
WARE: It’s a symbiotic relationship where we’re adapting to one another as we learn how to live together.
[Savage and Ware speak in the research collection.]
SAVAGE: We don’t drop our hot dogs, we drop our buns. And so, there’s a lot of carbs.
[An ant struggles to haul off a large crumb.]
SAVAGE: And we know that ants don’t have a long evolutionary history eating these weird foods that we drop. Our food is actually changing their behaviors.
[Hundreds of extremely tiny ants swarm over a piece of cake. A pavement ant colony rushes in and out of a small opening dug out under a landscaping light fixture. Ants crawl into cracks in the sidewalk.]
WARE: With a carb-heavy diet, rather than one full of protein, like they may have in more rural spots, Amy observed that ant colonies enter survival mode: they tighten up their colony size because they’re not able to support large numbers of workers.
[A group of ants moves a large fly carcass across the dirt of a median.]
WARE: And Amy’s research has shown that city ants are becoming more voracious predators: pouncing when they come across scarce insect prey and preferring crickets over corn chips.
[Savage and Ware look for ants in the street median.]
SAVAGE: One really cool thing about studying ecology and cities is that cities provide us a glimpse of one possible global future.
[Drone footage of a circular skyscraper with a lush green roof. People walk through Times Square.]
SAVAGE: We are an urban species now. It’s really fascinating to think about what does the future world look like.
[Tall buildings in Singapore are covered in vegetation—vines and trees growing down the sides and on the tops of structures.]
SAVAGE: I like going places like Singapore where there’s plants growing down the sides of buildings that help cooling down without air conditioning units. There’s walls of just vegetation that have a bunch of species flying all around them.
[Various buildings with exterior landscaping and small urban greenspaces that preserve patches of natural habitat.]
WARE: We often think of urbanization as kind of like a bad word, right? But what you’re saying is that urbanization can be done in a thoughtful way that could preserve some of the species diversity and the human health aspects that we like about rural settings?
[Savage and Ware speak in the research collection.]
SAVAGE: It could and, you know, I always have this vision of people walking through a city the way that they walk through a forest in a hike.
[Savage, standing in a street median, examines a tiny ant in a vial with a hand lens.]
SAVAGE: How can we look to nature to make our cities more of a place that we want to be?
[On a sidewalk, people stroll by a hot dog vendor and a large tree. Zoom in to the tree bark and an ant scurries past.]
WARE: While we still have a lot to learn about urban ecosystems, if we’re aware of the small players all around us, we’re more tuned in to the idea of a city as our habitat and what we and our tiny neighbors need to thrive.
[People walking, sitting, and eating in New York City’s Bryant Park—a green space spanning a couple of blocks and surrounded by tall buildings. Close-up of a tiny single ant crawling over a leaf.]
[Credits roll.]
[Close-up of pavement ants walking back and forth over sandy soil.]
WARE: You might have seen some cool pavement ant behavior without even realizing it.
[Ware speaks to camera in the Insectarium.]
WARE: Maybe you overlook them when it's a single individual walking around. But you may have seen pavement battles…
[Hundreds of tiny ants swarm in a cluster around a curb. A gap divides them into two sides.]
WARE: …where there's large groups of pavement ants that will kind of line up facing each other with a little bit of a gap between them.
[Ware speaks to camera in the Insectarium.]
WARE: It’s not so much like a battle as it is almost like a dance-off. You know, if you've seen West Side Story—very West Side Story.
[Pavement ants scurry around a small entrance to their colony on a sidewalk. Extreme close-ups of pavement ants running across stony blocks.]
WARE: Like their name suggests, pavement ants like to live under slabs of concrete and they’re very territorial.
[Close-up footage of ants grappling with one other. Ants are locked together with their forelegs and are pulling and biting at each other.]
WARE: Their battles usually happen in the spring and early summer when they’re trying to establish their territory.
[A blanket of tiny ants covers a spot on pavement, thousands of individuals battling.]
WARE: These are turf wars where the conflicts can go on for hours or even days! While there’s plenty of pulling and wrestling—and some ants are definitely killed—fatalities are comparatively low.
[Extreme close-ups of pavement ants fighting. Low angle of pedestrians wearing sneakers, heels, loafers, etc. crossing a city street.]
WARE: So, keep an eye on the sidewalks the next time you’re walking around the city and appreciate the world of tiny wildlife!
[A single ant runs up a blade of grass.]
In pavement cracks, roadside medians, and parking lots, there are incredible miniature civilizations booming within our concrete jungles: ants! We don’t often think of urban areas as having “ecologies” but Amy Savage, Ph.D. studies the amazing diversity of ants making their way in the city. Their combined efforts make our urban landscapes greener places to live, but their newfound love of carbs is also changing things for them...
Our host and museum curator, Jessica Ware, Ph.D. joins Amy in a search for some tiny neighbors. They're managing surprisingly well in New York and other cities by adapting to human food. But without the access to easy protein (e.g., other insects to prey on), they're doing things a bit differently in street medians than they would in a more rural setting.