I’ve written before about animal culture (a set of socially-learned behaviours specific to a given group). I’ve also written about animals’ adaptation to urban life. This time I write about both: animal culture that is an adaptation to urban life.
The main characters in this story are sulphur-crested cockatoos (Cacatua galerita) – large-brained, highly social parrots native to Eastern Australia (and other islands in the region). They naturally live in forested areas, but are increasingly common in cities, especially in the suburbs. While their natural food (seeds, nuts and fruits) might be scarce in the cities, there are plenty of other food sources, for example human food waste. But obtaining this food is actually not easy if it’s stored in bins with big and relatively heavy lids.
However, some birds discovered how to open these household waste bins.
To learn how common opening of the waste bins is in urban cockatoos an international group of researchers observed individually-marked birds and asked residents of Sydney and surroundings to record the behaviours of cockatoos over two years (2018 and 2019).
The data showed a fast spread of the behaviour from 3 suburbs to 44 in a way that is consistent with social learning. Over time the frequency of the behaviour increased within a suburb and spread to other areas, further and further (although in some neighbourhoods parrots opening bins were never observed). In one of the locations the cockatoos appeared to independently discover bin opening.
Flipping over the bin lid needs a coordinated sequence of different movements – opening the lid, holding it while walking towards the hinges and eventually flipping the lid completely open. There were differences in how individual birds opened the bins – for example whether they were walking on the left or right side of the bin rim or whether they would open the lid with one foot on it or not.
But there were also clear differences between locations in, for example, whether the birds would grab the handle or the rim of the lid when opening it, or whether their head was upside down (or not) when opening the lid. The further apart the locations, the larger the difference between the birds’ opening technique. These regional differences show the emergence of local subcultures in bin opening.
In many cases birds were observed trying to open a bin, but without success. Most of the birds trying to or opening the bins were males which suggests that this behaviour may demand quite some muscle power as males are heavier than females in this species. Additionally, males are more dominant and they could have priority accessing the food. But more studies are needed to figure out the cause of the sex differences and who exactly learns from whom.
Keep an eye out for unusual animal behaviour in your own neighbourhood. You might be the first to record an innovation that will lead to a discovery of a new animal culture!
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Photo: Photo by Gilberto Olimpio from Pexels