When Animals Take the Night Shift
They’d rather eat in the dark than risk coming across one of us.
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.
The study of what scientists call “human-induced evolution” took off almost 20 years ago, when the marine ecologist Stephen R. Palumbi, writing in the journal Science, said that humans “may be the world’s dominant evolutionary force.” Of course, humans have been deliberately manipulating plants and animals to bring out preferable traits for ages (Exhibit A: beagles, mastiffs, and Chihuahuas). But we also induce evolution in less intentional ways. For instance, Chris Darimont, a conservation scientist at the University of Victoria, in British Columbia, points to a simple mechanism he calls “selective killing”: Keeping all the big salmon and letting the little ones slip through the nets gives the smaller salmon a survival advantage, bringing down the species’ overall size.
theatlantic.com |
