They’d rather eat in the dark than risk coming across one of us.
By William Brennan
Several years ago, Kaitlyn Gaynor and her colleagues noticed an intriguing pattern. It started with data from Tanzania, where motion-detecting cameras captured a trend: Antelope that had once roamed primarily in the day were now roving more at night. As Gaynor, a doctoral candidate at UC Berkeley, and her fellow researchers discussed the change, they realized that a similar nocturnal shift had occurred in many other mammals, too. In Mozambique, elephants had begun traveling on roads in the dark, when they were relatively free of humans, and staying in the forest by day; in Nepal, tigers were moving about more often by moonlight, while people slept; in Poland, boars living in a national park split their days evenly between waking and sleeping, while urban-dwelling boars were awake almost exclusively at night. Once the nocturnal phenomenon “was on our radar,” Gaynor told me recently, “we started seeing it, really, everywhere.” Everywhere is no exaggeration: In a paper published in June, Gaynor and her co-authors offered evidence of nocturnal shifts in dozens of species that come into regular contact with humans, on every continent but Antarctica. Gaynor suspects that these behavioral changes are bringing with them rapid evolutionary change as well.
