Residents of almost any city in North America know how frustratingly clever raccoons can be. They break into garages, pilfer supposedly unreachable bird feeders and ransack trash bins, even defeating lids specifically designed to thwart them.
Despite their reputation, little is known about why raccoons are so good at urban living.
Over the past few years, researchers have taken to the streets of Laramie, Wyo., to uncover the raccoons’ secrets, adapting a cognitive test designed for captive animals so that it can be deployed in the wild.
Preliminary findings suggest that the most docile animals learned to use the testing devices more easily than bolder, more aggressive ones did, a result that has implications for our relationship with urban wildlife. The study was published on Thursday in the Journal of Experimental Biology.
As the planet is increasingly urbanized, the questions of which animals will be able to cope with the sprawl and why are becoming more urgent. The answers could be key to mitigating the conflicts that interspecies proximity brings and may point to better ways to manage animals as they are forced to share more of their habitat with us.
“The more that we know about their behavior and their cognition, I think it can really aid us in figuring out how to coexist with them,” said Lauren Stanton, a cognitive ecologist at the University of California, Berkeley, and lead author of the new study.
In their natural environments, animals deal with all sorts of pressures that shape how they think and behave. Raccoons have to acquire food, avoid predators and cars, find mates, raise kits and navigate social landscapes that include both raccoons and other species, including humans.
“It’s hard to really replicate that in a captive setting,” Dr. Stanton said.
Previous studies on how raccoons think have suggested they are indeed canny creatures, but nearly all of that work has been done in captivity. To get better insight into the animal’s real-world behavior, the researchers employed a classic learning test housed inside of a two-and-a-half-foot-tall wooden box.The test involves choosing between two options — in this case, pressing one of two buttons — only one of which results in a food reward.
Once the animal learns to consistently press the reward button, the task is reversed so the other button delivers the food. Scientists are interested in how quickly animals pick up on the change.
The researchers tested the cognitive flexibility of wild raccoons in Laramie, a city of around 32,000 people and the home of the University of Wyoming, where Dr. Stanton worked as a graduate student during the study.
Lauren Stanton, the study’s lead author, released a raccoon after it was implanted with a transponder.Credit…Stanton et al., Journal of Experimental Biology, 2022
The scientists trapped 204 raccoons that were roaming in backyards, alleys and parks across the city and set them free after implanting tiny transponders, devices similar to microchips used to identify pets, under their skin. Then they placed the wooden boxes, each equipped with two large LED buttons, a food chute, a small computer and night-vision cameras, where raccoons tend to hang out.
It took two years, but eventually 40 of the tagged raccoons were detected by antennas attached to the boxes. Nineteen of them figured out how to push the buttons to get food rewards, and 17 participated in multiple reversal trials.
The data for seven of them was unusable, mostly because other raccoons interfered during the testing. Two would squeeze in at the same time, and other times, a raccoon would push another out in the middle of a trial. One raccoon named Chive was doing great on the task each night until her performance suddenly plummeted. The camera footage revealed she had shown up with a litter of kits. “The babies were basically walking all over the buttons and creating chaos inside the testing device,” Dr. Stanton said.
In the end, data for 10 raccoons was included in the researchers’ analysis of learning flexibility. Seven of them improved, making fewer mistakes each time the reward button was reversed.
The results add more evidence that many animals are most likely evolving to thrive in landscapes created by humans, said Brian Hare, an evolutionary anthropologist at Duke University who was not involved in the study.
“The deer who constantly visit the compost pile outside the window of my suburban home are probably not surprised by this result,” Dr. Hare said.
Dr. Stanton’s team also wanted to know if certain characteristics made a raccoon more likely to excel on the test. They noted each animal’s behavior throughout the trapping and tagging process and found that individual raccoons reacted differently to the stress of being captured: Some were aggressive, hissing at the researchers, whereas others were quiet in their traps.
The scientists had expected that bolder raccoons would be more likely to interact with the testing devices. “But this isn’t what we found,” Dr. Stanton said.
It took two years, but the boxes eventually detected 40 tagged raccoons, 17 of which participated in multiple reversal trials. Sometimes, other animals snuck in. Video by Stanton et al., Journal of Experimental Biology 2022
Instead, the docile raccoons were more likely to learn how the devices work. The surprising discovery has implications for how cities deal with raccoons.
Urban wildlife management tends to focus on aggressive animals that may be confronting people and their pets, noted Sarah Benson-Amram, a behavioral ecologist at the University of British Columbia and a co-author of the study. By neglecting the docile animals, we may be increasing the proportion of problem-solving raccoons living in cities.
“Maybe they’re the ones who are learning how to open up the chicken coops and steal your chickens or break into your attic,” Dr. Benson-Amram said.
The results of the study add to a growing body of research suggesting animals that aren’t as aggressive or stressed by the presence of people may also have cognitive skills that help them thrive in urban areas.
“This is perhaps the first step towards domestication,” said Benjamin Geffroy, a biologist at the University of Montpellier in France. “Now we need to know more about what comes first, docility or cognitive abilities.”
Some research suggests the process of domestication changes how animals think. Dogs, for example, are better than wolves or nonhuman primates at following some human gestures, such as pointing to hidden food.
This does not necessarily mean that raccoons will soon be reading our gestures. But living alongside animals that may be evolving to exploit our presence might mean people need to better understand how the animals think in order to avoid conflicts with them, the researchers said.
Raccoons, however, could be particularly difficult. Working with captive raccoons has convinced Dr. Benson-Amram that they actually enjoy cognitive challenges. “We give them problems, and even when there’s no reward, they just keep going for it,” she said.
Raccoons in urban environments can also be remarkably persistent, said Suzanne MacDonald, an animal behavior scientist at York University in Toronto. For one study, she put an open can of cat food in a trash bin, secured the lid with a bungee cord and deployed it in backyards to see how raccoons would react.
“I had one female spend like eight hours trying to get in,” Dr. MacDonald said. “And she did.”
Raccoons are often perceived as invasive, Dr. MacDonald said, but humans are the ones who invaded their land.
“These guys have figured out a way to live with us,” she said. “Surely to God, we can use our giant cortexes and figure out a way to live with them.”
Betsy Mason is a freelance journalist and a 2022 Alicia Patterson Foundation fellow.