Quirks & Quarks

How trash bandits, furry and feathered, outsmart humans for food

In their quest for food, animals venture into human environments to access one of the richest urban food sources: garbage. Two new studies published this month detail how cockatoos and raccoons, two notorious trash bandits, are using their smarts to overcome human obstacles and fill their stomachs.

'This is really like the beginning of an innovative arms race,' says cockatoo researcher

Two new studies published this month detail how cockatoos and raccoons are using their smarts to overcome human obstacles and fill their stomachs. (Barbara Klump/Max Planck Institute of Animal Behavior, Tom Middleton/Shutterstock)

In their quest for food, animals across the world are venturing into human environments to access one of the richest urban food sources: garbage.

And as human-wildlife conflicts increase, some scientists are noticing just how good some animals are at adapting to — and often outwitting — humans. 

Two new studies have detailed how cockatoos and raccoons, both notorious trash bandits, are using their smarts to overcome human obstacles and fill their stomachs.

Australia's trash parrots

In Sydney, Australia, clever cockatoos have perfected the skill of opening trash bins using their beaks and legs. Since the birds toss the garbage everywhere looking for the tastiest tidbits, Sydney's other highly intelligent species — humans — has been experimenting with ways to outwit the birds. 

A study published in Current Biology earlier this month documents how humans and cockatoos are racing to outsmart each other.

A large grey-white bird opens a plastic garbage bin with a red lid using its beak by a house in a suburb of Sydney, Australia.
A sulphur-crested cockatoo pries open the lid of a garbage bin with its beak in Sydney, Australia. (Barbara Klump/Max Planck Institute of Animal Behavior)

Barbara Klump, lead author of the study, and a behavioural ecologist at the Max Planck Institute of Animal Behavior, said the birds learn how to open trash cans by observing one another, via a sort of cultural transmission of information.

"This is a cultural trait, which means that each group of cockatoos has their own little technique for how they open the bins, and they transmit that socially," said Klump.

"So, if you look at cockatoos that are far apart, they will also have more diverse techniques of how they open the bins."

But it turns out that the cultural transmission goes both ways.

Klump and her team found that people living on the same street or neighbourhood used different techniques to protect their bins compared to people living in another neighbourhood.

"There seems to be very similar learning strategies at play," said Klump.

Two large grey-white birds sit by a plastic garbage bin with a red lid. One bird looks on as the other hold the lid open with its beak.
A cockatoo pries open the lid of a garbage bin with its beak, as another cockatoo looks on. (Barbara Klump/Max Planck Institute of Animal Behavior)

The study documented more than 50 different measures Sydney residents developed to protect their garbage. One of the most common measures involved putting something heavy, like a brick, on top of the bin to prevent it from opening.

Other techniques involved tying a string between the lid and rim to prevent the lid from opening completely, or placing an item between the lid and the hinges, like a pool noodle or shoes, to prevent the cockatoos from flipping the lids open. 

But Klump said Australia's trash parrots are already finding ways to outmaneuver some of these measures, such as pushing the heavy objects off of the lid.

"We are thinking this is really like the beginning of an innovative arms race that we're seeing here," said Klump.

North America's adaptable raccoons

Human-wildlife conflict isn't uncommon, but Sarah Benson-Amram, a cognitive ecologist at the University of British Columbia, says it's rare to have data "that document this sort of innovation arms race from both the human and animal side."

Benson-Amram, who was not involved in the cockatoo study, has been studying the cognitive abilities of raccoons for years. In North America, she says the furry creatures — often referred to as trash pandas — are filling "a pretty similar" role to Australian cockatoos.

This week, she and her team published a study in the Journal of Experimental Biology that suggests a raccoon's personality may play an important role in how good it is at accessing garbage and adapting to human environments.

The mischievous raccoon seemed like the perfect candidate for her research because of their reputation for being clever and capable of overcoming any and all human obstacles.

Raccoons are known for raiding people's garbage in urban environments. (Shutterstock)

The team studied wild raccoons living in Laramie, Wyo., for two years. They found that the most calm, docile and shy raccoons are better adapted to city environments.

To learn this, they built four raccoon-sized cubicles in the animals' neighbourhoods. The cubicles had two buttons: when pressed, one button released a handful of dog treats. The other button released nothing.

After the raccoons learned to climb into the cubicle and press the correct button to obtain treats, researchers switched things up by changing which button released the edible reward. 

The more docile raccoons, they found, were best at adapting to the change and pressing the correct button.

A wild raccoon receives a handful of dog treats after pressing the correct button in an outdoor research cubicle. (Lauren Stanton)

Benson-Amram says this displayed certain raccoons' "behavioural flexibility," or their ability to change their own behaviour when their surrounding environment changes.

"We think that this is potentially really important for animals that are living in human-modified environments, because cities can be really variable in what resources are available."

The findings have significant implications for how cities manage human-wildlife conflict, said Benson-Amram.

"We think from a management perspective, if we just focus on removing bolder, more aggressive animals, we may actually be sort of unknowingly selecting for these quieter, smarter individuals," she said. "That may lead to more conflict in the future."


Produced and written by Maya Lach-Aidelbaum.

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