A group of raccoons rummaging through garbage on the street

TRASHED! Raccoons commonly raid unlocked garbage bins in search of food because they are attracted by the smell.

S AND D AND K MASLOWSKI/FLPA/MINDEN PICTURES

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Investigate It!

Masked Bandits

Scientists have discovered that the calmest raccoons might also be the most mischievous

AS YOU READ, THINK ABOUT how living alongside humans affects wildlife.

Clank! Bang! Crash! You’re awakened by a noisy commotion outside. You jump out of bed and open the curtains. The garbage cans by the curb are toppled—trash is scattered everywhere. Out of the mess pokes a furry head with glimmering eyes ringed in black. It’s a raccoon!

Raccoons raid trash bins, hunt chickens in coops, and nest in homes across the United States. This can result in human-wildlife conflicts—negative encounters between people and wild animals that can put both at risk (see People vs. Animals). Raccoons can be seen as threats to people’s safety, property, or livelihoods. As a result, people may retaliate against the animals to get rid of them. When it comes to raccoons, animal control officials usually aim to remove the most aggressive individuals—assuming they’re the biggest troublemakers.

Clank! Bang! Crash! Loud noises outside wake you up. You jump out of bed and open the curtains. The garbage cans by the curb are toppled. Trash is everywhere. A furry head pokes out of the mess. Its shining eyes are ringed in black. It’s a raccoon!

Raccoons raid trash bins across the United States. They also hunt chickens in coops and nest in homes. This can result in human-wildlife conflicts. These negative encounters between people and wild creatures can put both at risk (see People vs. Animals). People can see raccoons as threats to their safety, property, or livelihoods. So they may fight back against the animals to get rid of them. Animal control officials usually try to remove the most aggressive raccoons. They think these animals are the biggest troublemakers.

EVAN FROST/MINNESOTA PUBLIC RADIO VIA AP IMAGES

CLIMBING CRITTERS: This raccoon went viral across the internet while climbing up the side and to the top of the 25-floor-tall UBS tower in St. Paul, Minnesota, in June 2018. It’s pictured here scratching an itch on a 23rd-floor windowsill. The raccoon was later captured and released into the wild.

But scientists from the University of Wyoming wondered if that was true. Are aggressive raccoons really the most mischievous? Or are the more docile, or calm, raccoons really the troublemakers? The researchers launched an investigation to find out if raccoons’ temperaments, or overall personality, affected their ability to adapt to a changing environment.

The growth of cities and suburbs has greatly reduced raccoons’ natural habitat. “Because we change their landscape, these animals are just figuring out how to survive,” says Lauren Stanton, who led the study. Stanton, who now works at the University of California, Berkeley, is a cognitive ecologist—a scientist who studies how animals think in different situations. “It’s important to study raccoons so we can figure out ways to better coexist with them,” she says.

But is that true? Scientists from the University of Wyoming wondered about it. Are aggressive raccoons really the most trouble? Or are the real troublemakers the more docile, or calm, raccoons? The researchers decided to study raccoons’ temperaments. They wanted to find out if raccoons’ personalities affected the way they adapt to changes where they live.

Cities and suburbs have grown. That has greatly reduced raccoons’ natural habitat. “Because we change their landscape, these animals are just figuring out how to survive,” says Lauren Stanton, who led the study. Stanton now works at the University of California, Berkeley. She’s a cognitive ecologist—a scientist who studies how animals think in different situations. “It’s important to study raccoons so we can figure out ways to better coexist with them,” she says.

FURRY TEST SUBJECTS

Scientists have studied the behaviors of raccoons before, but almost always in laboratories. Stanton and her team wanted to test how wild raccoons adapt to changes in actual settings with humans. So the researchers set up cage traps in Laramie, Wyoming, to capture raccoons.

The scientists caught 204 of them. They recorded each animal’s approximate age, gender, and temperament. A raccoon was categorized as “aggressive” if it growled, snarled, hissed, or tried to swipe at researchers with its claws. Those that acted calmly were labeled as “docile.” The scientists wanted to see if temperament influenced how well the animals could solve human-made challenges.

Once the initial assessment was complete, each animal was fitted with a tracking tag and released back into the city. The tags emitted radio signals so the scientists could keep tabs on the raccoons.

Scientists have studied the behaviors of raccoons before. But almost all studies took place in laboratories. Stanton and her team wanted to test wild raccoons in actual settings with humans. The team would observe how these raccoons adapted to changes. So the researchers set up cage traps for raccoons in Laramie, Wyoming.

The scientists caught 204 raccoons. They recorded each animal’s approximate age, gender, and temperament. Some raccoons growled, snarled, hissed, or swiped at researchers with their claws. Those animals were labeled as “aggressive.” Others acted calmly. They were labeled as “docile.” The scientists wanted to see how well each animal solved human-made challenges. Would temperament affect their performance?

After the scientists checked each animal, they fit it with a tracking tag. Then they released it back into the city. The tags sent out radio signals, so the scientists could keep tabs on the raccoons.

SUZI ESZTERHAS/MINDEN PICTURES

The dark fur around a raccoon’s eyes may reduce glare to improve their night vision.

PICK A BUTTON

Next, Stanton’s team devised a test for the raccoons. The researchers placed wooden boxes around Laramie. Each had an open doorway big enough for just one raccoon to enter at a time. This would allow scientists to gather accurate data about each animal without disruptions.

Inside the box were two illuminated buttons. The researchers placed some food behind the buttons to motivate a raccoon to touch them. Hidden video cameras recorded the animals’ behaviors from both outside and inside the boxes.

At the start of testing, the raccoons could push either button and receive a treat—dry dog food. If a raccoon pressed either button 11 times, a more difficult test began. Now only one of the buttons would deliver a treat. The researchers measured how long it took each animal to learn which button gave a reward.

If a raccoon correctly pressed the treat button 9 out of 10 times, the buttons’ responses would switch. Food would now be dispensed only by pressing the opposite button. The scientists did this “reversal test” to determine whether the raccoons would realize the change and adapt their behavior by learning to press the other button. But as soon as testing began, Stanton and her team ran into some trouble.

Next, Stanton’s team arranged a test for the raccoons. The researchers placed wooden boxes around Laramie. Each had an open doorway. Just one raccoon could fit through at a time, so other raccoons wouldn’t interrupt. That way, scientists could gather accurate data about each animal.

Two lighted buttons were inside the box. The researchers placed some food behind the buttons to get a raccoon to touch them. Hidden video cameras were set up both outside and inside the boxes. They recorded the animals’ behaviors.

At first, the raccoons could push either button and receive a treat. It was dry dog food. If a raccoon pressed either button 11 times, a more difficult test began. Now only one button would deliver a treat. The raccoons had to learn which button to push. The researchers measured how long each animal took to figure it out.

If a raccoon pressed the correct button 9 out of 10 times, the buttons’ responses would switch. Now only the opposite button would deliver food. The scientists did this “reversal test” to see if the raccoons would change their behavior. Would they realize the change and learn to press the other button? But when testing began, Stanton and her team ran into some trouble.

RASCALLY RACCOONS

The wooden test boxes turned out to be popular with the hungry raccoons—too popular! Multiple animals would fight to squeeze their way in to get a snack, disrupting the experiments. “We assumed the raccoons would go inside one at a time, but that’s not what happened,” says Stanton. “We’d put a box in the field, and then a bunch would try to gain access.”

If more than one radio tag was detected by sensors inside the box, the experiment would end. Of the 40 total tagged raccoons that entered the boxes, 19 learned to push the buttons. Of those, 17 learned the reversal test. And only 10 of them were studied individually and without interruption. In the future, “we have to figure out how to test the raccoons when they all want to be in the device at the same time,” says Stanton.

The scientists also observed that the more time spent interacting with the buttons, the fewer mistakes raccoons made. They learned to quickly switch to the opposite button once food stopped dispensing from the box.

The wooden test boxes were popular with the hungry raccoons—too popular! Many raccoons wanted a snack. They fought to squeeze in and interrupted the experiments. “We assumed the raccoons would go inside one at a time, but that’s not what happened,” says Stanton. “We’d put a box in the field, and then a bunch would try to gain access.”

Sensors were placed inside the box. If they detected more than one radio tag, the experiment would end. In all, 40 tagged raccoons entered the boxes. Nineteen learned to push the buttons. Seventeen of those learned the reversal test. And only 10 of them were studied alone, without interruption. In the future, “we have to figure out how to test the raccoons when they all want to be in the device at the same time,” says Stanton.

The scientists noticed something else. If raccoons spent more time pushing the buttons, they made fewer mistakes. When food stopped coming from the box, they quickly switched to the opposite button.

COURTESY OF LAUREN A. STANTON, PH.D.

RACCOON RELEASE: Lauren Stanton releases a raccoon after it has been tagged.

Overall, raccoons adapted well to the human-made challenge. They are extremely intelligent, so the results weren’t a big surprise. But scientists were surprised by the role animals’ temperaments played. They assumed that the aggressive raccoons would be better at getting food. That wasn’t the case. The docile raccoons performed the task better. This means that “the docile animals might actually be better at figuring out problems like getting into garbage cans and chicken coops,” says Stanton. Capturing aggressive animals might not be the best way to prevent human-raccoon conflicts after all!

Instead, Stanton suggests that people secure garbage cans, compost bins, and chicken coops so raccoons can’t open them. People should also make sure to fix holes in the outer walls of buildings and cap chimneys so raccoons can’t get inside. And never feed raccoons—the animals will keep coming back, just like in the experiment. “It’s up to us to recognize raccoon attractants and do our best to deter them,” says Stanton. “These animals are just trying to survive in the environments we created.”

Overall, raccoons adapted well to the human-made challenge. They are extremely intelligent, so the results weren’t a big surprise. But one thing did surprise scientists. It was the role of the animals’ temperaments. The scientists thought that the aggressive raccoons would be better at getting food. That didn’t happen. The docile raccoons performed the task better. This means that “the docile animals might actually be better at figuring out problems like getting into garbage cans and chicken coops,” says Stanton. Officials have been capturing aggressive animals to prevent human-raccoon conflicts. That might not be the best plan after all!

Instead, Stanton suggests other actions. People should secure garbage cans, compost bins, and chicken coops. Make sure raccoons can’t open them. Be sure to fix holes in the outer walls of buildings and cap chimneys. That way, raccoons can’t get inside. And never feed raccoons. The animals will keep coming back, just like in the experiment. “It’s up to us to recognize raccoon attractants and do our best to deter them,” says Stanton. “These animals are just trying to survive in the environments we created.”