You’ve heard of trash pandas: raccoons looting trash cans. What about garbage parrots?
Sulfur-crested cockatoos, which may seem exotic to Americans and Europeans, are everywhere in the Sydney suburbs. They have adapted to the human environment, and since they are known to be adept at handling objects, it’s not entirely surprising that they turned to a rich source of food. But you could argue that the spread of their latest tip, to open the trash cans, blew the lid off social learning and cultural evolution in animals.
Not only do birds learn the skill by imitating others, which is social learning. But the details of the technique evolve to differ among groups as innovation spreads, a hallmark of animal culture.
Barbara C. Klump, behavioral ecologist at the Max Planck Institute for Animal Behavior in Germany, and first author of a cockatoo research report in the journal Science, said: “It’s actually quite complex behavior. because it has several stages. “
Dr. Klump and his colleagues divided the behavior into five movements. First, a bird uses its beak to remove the lid from the container. Then, she said, “they open it, then they hold it, then they walk along one side and then they turn it over. And at each of these stages, there are variations.
Some birds walk on the left, others on the right, they walk differently or hold their heads differently. The process is similar to the spread and evolution of human cultural innovations like language, or a classic example of animal culture, birdsong, which can vary from region to region within the same species.
Dr Klump and his colleagues in Germany and Australia have traced the spread of the behavior in greater Sydney over the course of two years. The behavior became more common, but it did not appear in random places, as it might have been if different birds discovered the trash technique on their own. It spread outward from its origin, indicating that cockatoos were learning to do this from each other.
The new cockatoo skill unlocks a whole new resource for birds. It is an adaptive cultural evolution, spreading at lightning speed compared to biological evolution. Dr Klump noted that cultivation has been called a second inheritance system and one that applies to both humans and animals, allowing us and them to adapt and quickly change our behavior.
It’s impossible to know which bird or birds first developed the trash can technique, but apparently there isn’t a single cockatoo genius. During the study, the behavior appeared a second time in a suburb too far from the first for the spread to be through social learning, said Dr Klump. The technique is invented again.
Scientists have observed social learning and what they call culture in primates, songbirds and other animals. Different groups of chimpanzees exhibit slightly different patterns of tool use, for example, as cockatoos did.
The researchers didn’t just look at different techniques in different fields. They also tagged and observed a hundred cockatoos to better understand individual behavior.
They found that about 30 percent of the birds tried to open the trays and about 10 percent were successful. Most of the successful birds were males. Dr Klump said men are successful because they tend to be bigger and may be better able to cope with physical demands. Or it could be that they have a higher rank and normally have the first access to food.
But what about the birds that didn’t try to open the bins? Weren’t they just smart enough or big enough? Not necessarily, Dr Klump said, because once the trays were opened any cockatoo could join in and feed without doing any work. Maybe, she said, they have a strategy: “This bird can do it – I’ll just wait for them to open it. Whether this is true is a subject for future research.
Mark O’Hara of the University of Veterinary Medicine in Vienna, who studies Goffin’s wild cockatoos in Indonesia, said the study “beautifully combines citizen science with rigorous direct observations.”
He said he was particularly interested in the larger and higher-ranking parrots doing the work of exploiting the new resource. “In primates,” he said, “lower-ranking individuals would have to find new ways to access food, while the stronger dominant individuals could simply move and exploit these ‘findings’.”
The first species of parrot known to open trash cans was the New Zealand kea in a park. But in this case, said Dr O’Hara, humans have nipped cultural evolution in the bud.
“It would have been interesting to see how the kea would have developed over time, but unfortunately the park weren’t too happy with the downshifts and changed the lids on the trash cans.”