Rural owl species doesn't mind the stress of city life

BAHIA BLANCA, Argentina, Sept. 17 (UPI) -- The majority of species prefer to avoid the encroachment of urban development. In fact, most endangered species are in the predicament they're in due to habitat loss at the hands of growing populations and expanding development.

But a few species aren't fazed by city living, and some flourish in urban environs. One of those species is the burrowing owl (Athene cunicularia), a small, long-legged bird found in South America and the American West. And now, scientists are keen on what makes some city dwellers so adaptable.

According to researchers at Pablo de Olavide University (UPO), a public university in Spain, the burrowing owl has been observed rapidly colonizing the Argentine city of Bahia Blanca, near Buenos Aires. According to their recent study on the owl's urban success, one of the species' key attributes is its calm, cool demeanor -- a buffer against the stresses of life among city folk.

In measuring levels of corticosterone, a stress response hormone, in both rural and urban owl specimens, researchers found the burrowing owl to be seemingly stress free.

"Despite the fact that the urban and rural individuals differed in the exposure they have to disturbances and the comfort distance from people, we did not find any differences in the levels of the stress hormone," Martina Carrete, a researcher at UPO, said in a press release.

While stress levels didn't differ on the whole, researchers did find individual differences in corticosterone levels. For city dwellers, these levels were key to survival. High levels of the hormone were linked to negative health effects and a higher risk of mortality, while low levels were found among thriving urban specimens. Meanwhile, in the country, corticosterone levels weren't linked with an improved or diminished chance of survival.

The study, published in the journal Nature, suggests that burrowing owls with the lowest corticosterone levels are most likely to colonize the city.