Living With City Critters Ratios & Proportions Article for Students

Lincoln Park Zoo, Urban Wildlife Institute

Seth Magle sets up a camera trap to record the animals that live in a city park.

Four times a year, wildlife biologist Seth Magle heads into the field to look for animals. He spends hours driving to his research sites. Then he hikes to a series of spots he’s selected and sets up motion-activated cameras. They will photograph the wildlife he’s studying. But he’s not searching for rare species on a far-flung continent—Magle is visiting parks, cemeteries, and golf courses in the bustling city of Chicago.

Magle is the director of the Urban Wildlife Institute (UWI) at Chicago’s Lincoln Park Zoo. He and his colleagues study animals that make their home in the city—everything from squirrels and pigeons to raccoons, opossums, coyotes, and more. “People are often surprised when I tell them that we know a lot more about the lions in the Serengeti than we know about the squirrels in our own backyard,” he says. “But if we want to connect people to nature, a natural place to start is where they live.”

Seth Magle is a wildlife biologist. He looks for animals four times a year. Driving to his research sites takes hours. When he arrives, he hikes to a series of spots. There, he sets up motion-activated cameras that photograph wildlife. But he’s not searching for rare species on a far-flung continent. Magle is visiting parks, cemeteries, and golf courses in Chicago.

Magle is the director of the Urban Wildlife Institute (UWI) at Chicago’s Lincoln Park Zoo. His group studies animals that call the city home. It studies squirrels, and pigeons, raccoons, opossums, coyotes, and more. “We know a lot more about the lions in the Serengeti than we know about the squirrels in our own backyard,” he says. That surprises many people. “But if we want to connect people to nature, a natural place to start is where they live.”

One reason Magle’s work is surprising is that people don’t always think fondly of the animals they share cities and suburbs with. Squirrels are notorious for stealing from bird feeders, and opossums will nest in people’s attics or under sheds. “Raccoons create conflict because they get into our garbage,” says Magle. “Geese and pigeons? Well, they poop on everything.”

But we shouldn’t hold these behaviors against the animals, which are just following their natural instincts, says Magle. Raccoons are intelligent and omnivorous—meaning they eat many different types of food—so unsecured garbage is an easy target. Pigeons evolved to nest on cliffs, and tall buildings make a good substitute. Geese like vast expanses of short grasses they can graze on, and that’s exactly what they get in a sprawling city park or golf course. “We have just built a giant goose buffet, so we shouldn’t be surprised when they show up and use it,” Magle says.

Partly because we perceive these common critters as pests, scientists haven’t always paid much attention to them. But Magle and others are now trying to learn more about their habits, populations, and abilities. Sarah Benson-Amram is an urban ecologist at the University of British Columbia in Canada. She designs food puzzles to test how raccoons learn new things and solve problems. She’s found that they perform about as well as human children!

“The more we study this, the better we’ll be at designing effective mitigation strategies” to keep them from causing trouble for us, says Benson-Amram.

People don’t always like the animals that live in cities and suburbs. Squirrels steal seed from bird feeders. Opossums nest in attics or under sheds. “Raccoons create conflict because they get into our garbage,” says Magle. “Geese and pigeons? Well, they poop on everything.”

But these animals are just following their natural instincts, says Magle. Raccoons are smart and eat many different types of food. That makes garbage an easy target. Pigeons usually nest on cliffs. Tall buildings make a good replacement for them. Geese like large fields where they graze on short grasses. That’s exactly what they get in a sprawling city park or golf course. “We have just built a giant goose buffet,” Magle says. “We shouldn’t be surprised when they show up and use it.”

Scientists haven’t paid much attention to these common critters. But Magle and others are now learning more about their habits, populations, and abilities. Sarah Benson-Amram is an urban ecologist at the University of British Columbia in Canada. She designs food puzzles to see how raccoons learn new things and solve problems. She’s found that they perform about as well as human children!

As we learn more about them, we can figure out how to keep them from causing trouble for us, says Benson-Amram.

Magle and his colleagues want to understand how different species are using urban and suburban landscapes. Since 2010, they’ve set up cameras at dozens of sites around Chicago and left them there for a month every January, April, July, and October. Motion sensors trigger the cameras to turn on anytime an animal climbs, lumbers, or scurries in front of them. With help from volunteers, Magle’s team then tallies which animals—specifically mammals—were detected and where.

The data they collect can’t actually tell them how many of each animal is in the city, explains Mason Fidino, an ecologist and statistician at the UWI. That’s because there’s no way of knowing if two raccoon photos from the same camera are showing the same individual or different ones. But it can tell them which types of habitats around the city different species use and whether their ranges are growing or shrinking. And it can reveal patterns, like when opossum populations boom suddenly in some years and virtually disappear the next.

Over the years, the team has made some unexpected discoveries. Flying squirrels, which Magle assumed didn’t live in Chicago, are actually common—but they come out only at night. Beavers and otters, which used to be rare in the city’s rivers and streams, have been showing up more often. “I think it speaks to the fact that our waterways have really been cleaned up over time,” Magle says.

Magle and his colleagues want to understand how different species use the city and suburbs. They’ve set up cameras at dozens of sites around Chicago in the past 12 years. Every January, April, July, and October, they leave them out for a month. Anytime an animal climbs, lumbers, or scurries in front of a camera, the motion sensors turn the camera on. With help from volunteers, Magle’s team tallies which mammals passed by each camera.

The data the researchers collect does not show how many of each animal lives in the city, says Mason Fidino, an ecologist and statistician at the UWI. That’s because there’s no way of knowing if two raccoon photos from the same camera show the same individual. But the photographs can tell the team which habitats different species prefer. They also show whether an animal’s range is growing or shrinking. The data can also reveal patterns, like when opossum populations suddenly increase one year and nearly disappear the next.

Over the years, the team has made some surprising discoveries. Flying squirrels, a species Magle assumed did not live in Chicago, are actually common. But they come out only at night. Beavers and otters used to be rare in the city’s rivers and streams. Now they show up more often. “I think it speaks to the fact that our waterways have really been cleaned up over time,” Magle says.

Studying urban critters and their habitats can also tell scientists something about the health of the environment as a whole. The same things that might make an area welcoming for wildlife—like plenty of trees and clean air and water—make it more pleasant and healthy for people to live in, Fidino points out. So if animals avoid certain areas, it could mean improvements are needed for all.

In recent years, UWI staff have worked with scientists in other cities to collect data on their local wildlife. The UWI team also uses its research to educate the public about their animal neighbors, which can help reduce conflicts.

Fidino particularly loves talking about opossums and says he’s seen people’s attitudes toward them improve over time. “If you’re trying to teach people about conserving wildlife, it’s much easier if you can make connections to the wildlife they actually interact with,” he says. “And there are a lot of really great, charismatic species that live right beneath our noses that they may not even know about.”

Studying city critters and their habitats can also tell scientists about the health of the environment as a whole. An area with plenty of trees and clean air and water might make a place more welcoming for wildlife. It also makes a place and pleasant and healthy for people, too, Fidino points out. Locations animals avoid may need improvements for all living creatures.

UWI staff have also worked with scientists in other cities to collect data on their local wildlife. The UWI team uses its research to educate the public about their animal neighbors too. The information can help reduce conflicts.

Fidino particularly loves talking about opossums. He says people’s attitudes toward them have improved over time. “If you’re trying to teach people about conserving wildlife, it’s much easier if you can make connections to the wildlife they actually interact with,” he says. A lot of fascinating species “live right beneath our noses that they may not even know about.”

UWI scientists use motion-sensitive cameras to see which animals visit different sites. The percent of sites at which each species is detected tells them roughly how common it is in the area. The chart below shows the data collected on three species in four cities in April 2019. Use it to answer the questions. Round answers to the nearest percent. Record your work and answers on our answer sheet.