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.
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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, Wyoming, 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 their thinking and behavior. 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,” 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 a 0.76m-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.
A raccoon outside a box constructed to house a cognitive test in Laramie, Wyoming.
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 Stanton worked as a graduate student during the
study.
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, 340 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,” 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.
Lauren Stanton releases a raccoon after it was implanted with a transponder in Laramie, Wyoming.
“The deer who constantly visit the compost pile
outside the window of my suburban home are probably not surprised by this
result,” Hare said.
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,” Stanton said.
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,”
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 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.
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