What does it take for a person to adapt well to living in the big city? Other than a willingness to pay way too much to live in a tiny space with unkempt roommates, the ability to navigate crowded transportation arteries, and a penchant for relatively regular cheap fast food, certain deeply engrained personality traits can help. For example, people that are laid back are less likely to have an anxiety attack brought on by the continual contact with strangers. Those more willing to get out and explore – to put themselves out there, so to speak – are more likely to find community and the advantages offered by having a crap ton of stuff nearby.
The same can also be said for animals packing up their roosts and heading to the urban forest of skyscrapers. Studies have shown that birds inhabiting the big city are less easily stressed and more likely to explore novel objects and places. But are these personality traits learned by individual birds as they navigate the streets, or have these flocks evolved genetically to be a better fit for their chosen environment?
In a recent paper from Indiana University, scientists tried to get at this tiny riddle in the larger context of nature versus nurture. They captured a handful of infant dark-eyed juncos both from a population that has taken up in San Diego County and their brethren that haven’t strayed from their ancestral breeding grounds 50 miles away. These baby birds were then raised together in identical circumstances within an aviary in Bloomington.
After eight months’ time, the birds were put through a battery of tests to look at their stress response levels and willingness to explore. The researchers found that even though both sets were raised in identical circumstances, those from the city explored faster and more extensively, and had lower stress-induced levels of the hormone corticosterone. The latter points to slight modifications of the hypothalamic-pituitary-adrenal axis, a complex network of interactions between three glands that control stress reactions and regulate digestion, the immune system, mood, and energy usage.
Of course, there’s still the chance that the brief amount of time spent in their home nests before being swept away to Indiana caused the differences. Further genetic studies, however, should be able to tease out if there are indeed genetic mutations at the heart of the apparent adaptations.
“Boldness behavior and stress physiology in a novel urban environment suggest rapid correlated evolutionary adaptation” was co-authored by Danielle J. Whittaker of Michigan State University; Earlham College graduate Samuel Campbell-Nelson; then IU undergraduate Kyle W. Robertson; Goncalo C. Cardoso of the Universidade do Porto, Portugal; and IU Distinguished Professor Ellen D. Ketterson. Whittaker is a former postdoctoral researcher in the Ketterson research group, which is in the IU College of Arts and Sciences’ Department of Biology.