Urban settlements attract not only human residents, but also many creatures happily sharing the cities, scavanging on easy pickings.
But what makes some creatures better suited for life in urban environments than others? One particularly successful urban colonist, the raccoon, has taken North American cities by storm, yet no one has pinned down how.
A research team led by Lauren Stanton from the University of California, Berkeley, USA, published their discovery that the least bold and most docile animals are the most successful in a peer-reviewed study in the Journal of Experimental Biology.
The findings suggest that targeting the boldest raccoons when there is human conflict could exacerbate the problem, as the most docile animals that remain are most likely the true criminal masterminds trash raiders.
"Several cognitive abilities have been proposed as particularly important for urban wildlife," Stanton said.
While studying for her Ph.D. with Sarah Benson-Amram at the University of Wyoming, USA, Stanton, with Eli Bridge (University of Oklahoma, USA) and Joost Huizinga (OpenAI, USA), embarked on an ambitious study to get inside the heads of the urban mammals to find out what makes a great urban dweller.
"We used live traps baited with cat food to humanely capture raccoons living in the city of Laramie, Wyoming, " Stanton said, who then transported the animals to the lab to assess their health and how feisty or docile they were.
A tiny radio frequency ID tag was then injected between the animal's shoulder blades to individually identify them before returning the animals to their home territories, keeping track of their impulsivity by recording each time an individual ended up in a trap again.
Having tagged 204 raccoons between August 2015 and September 2019, the team then tested how well the wild raccoons learned and adapted to change by locating a raccoon-sized cubicle in the animals’ neighborhood, equipped with two buttons: one that released a handful of tasty dog food treats when pressed, and a second one that provided nothing.
Once each raccoon had overcome its misgivings and learned to climb inside the cubicle and obtain its edible reward, the team turned the tables on the animals, switching which button dispensed the reward to find out how quickly the raccoons figured out the change.
However, it seems that Stanton and her colleagues hadn’t factored in how popular the raccoon cubicle would be, with several animals often trying to crowd inside simultaneously, bumping and distracting the raccoon as it tried to obtain its dog food treat.
Yields of raccoon testing over the last two years
After two years of ongoing experiments, 27 raccoons got the hang of the cubicle, with 19 figuring out how to press the buttons to provide themselves with rewards, and 17 realizing that they had to switch buttons when the team tried to outfox them.
Initially, the youngest raccoons seemed the keenest to explore the experimental cubicle; however, the adults were better prepared for adversity when the researchers switched the buttons. And when they checked the animals’ temperaments.
"The least bold and most docile raccoons seemed best prepared to learn how to operate the console, which suggests a potential relationship between emotional reactivity and cognitive ability in raccoons," Stanton explained.
"The least bold and most docile raccoons seemed best prepared to learn how to operate the console, which suggests a potential relationship between emotional reactivity and cognitive ability in raccoons."
Lauren Stanton
When the researchers compared how the raccoons in the Laramie suburbs coped, in comparison with the wild raccoons that tried out their mettle in a peaceful lab environment, the captive animals seemed to pick up the test more readily, likely because there were fewer distractions and interruptions.