How a Garbage-Bin War Schools Humans and Birds

Forget the space race. In Sydney, Australia, the innovation arms race is real. It’s between humans and sulfur-crested cockatoos, and the battle is over the trash.

The cockatoos, which are native to Australia and frequent the suburbs, were already known to be trash-bin bandits. They open the lids using an innovative combination of prying up the front, lifting the lid, walking around to the side of the can and flipping the lid back. The clever birds learn about the behavior from one another, a type of cultural transmission. That cultural transmission, it turns out, goes both ways. In humans’ efforts to protect their garbage, they’re showing cultural transmission and innovation, too.

It’s “evidence that people socially learn from other people which protection methods to use, and that they are geographically clustered,” said Barbara C. Klump, the first author of a study published Monday in Current Biology, and a behavioral ecologist at the Max Planck Institute of Animal Behavior in Germany.

For a sulfur-crested cockatoo, a garbage bin is a big draw. “I’ve seen them eating chicken bones and ham sandwiches, but they really like bread,” Dr. Klump said. As the cockatoos hunt carbs, they scatter trash far and wide. The windy environment then turns a localized trash raid into a far-flung garbage disaster. It’s no surprise that people want to protect their bins.

In the study, Dr. Klump and her colleagues surveyed more than 3,000 trash bins in four suburbs of Sydney to see whether people had tried to protect their bins from birds. It’s not easy. The bins are emptied by a semi-automated arm on the top of the garbage truck. When the truck arrives, it picks up the bin and flips it over, automatically opening the lid to let the trash fall out into the truck. So whatever bird-proofing people try must still allow the bin to open.

“I think the most common one is just putting something heavy onto the lid,” Dr. Klump said. “It’s usually a brick or a rock.” Residents also tried deploying a rubber snake to scare the birds or placing an item between the lid and the hinges, like a pool noodle, a stick or shoes, to prevent the cockatoos from flipping the lids open. Some attached a rope to make sure the bin couldn’t open all the way — just wide enough for trash to spill into the truck.

Good defense ups the birds’ game. Dr. Klump has observed cockatoos using brawn as well as brains to shove bricks off bins to get the prize. It has changed garbage collectors’ behavior as well. When they lift a protected bin, “they give it one little shake, and then the brick or rock falls off and then they empty it,” Dr. Klump said. Sticks or pool noodles fall through the hinges to make emptying easy.

To show the behavior was socially learned, the scientists looked at the geographical distribution of trash protection and surveyed more than 1,000 residents. People and birds have a lot in common. Birds living close to one another learn to open bins in similar ways, and human neighbors tend to protect their trash using similar methods.

In the survey, 172 residents reported guarding their garbage. Being humans, 64 percent of the trash-can owners learned about new methods of bin protection from other people. As the birds prevailed over bricks and rocks, 61 percent of the residents who protected their bins changed their strategies. “Bricks seemed to work for a while, but cockies got too clever,” one survey respondent reported. “Neighbors on other side of highway suggested sticks. They work.”

The human-bird innovation arms race is “a really exciting idea,” said Sarah Benson-Amram, a behavioral and cognitive ecologist at the University of British Columbia in Vancouver. “It’s really wonderful to see data showing that likely this is what’s happening.”

Dr. Benson-Amram studies how animals respond to their environments. She thinks this behavior might extend to other human-wildlife interactions, like those involving African and Asian elephants that have learned to use their tusks or logs to burst through electric fences surrounding crops. Dr. Benson-Amram’s lab studies raccoons, another example of a trash bandit famous for outsmarting humans’ efforts to defend their garbage.

In Australia, it’s the birds’ move, and if Dr. Klump and her colleagues can show that methods to defeat bin protections also spread among local birds, the arms race will truly be on. Australians will have to come up with new defense methods and stay vigilant. It’s never good to be cocky.