Mammals turning into night owls

Many mammal species are so distressed by human activity, they are starting to live by night just to get away from us, a study has suggested. Researchers in the US drew on data from more than 70 previous studies to get an impression of 62 mammal species. When they cross-referenced the
results with levels of human disturbance – everything from road-building to hiking – they found that higher levels were associated with a 1.36 times increase in nocturnal activity, on average. The
phenomenon could be observed regardless of the type of human interference, and persisted when a species’ habitat was unchanged, leading the researchers to conclude that fear must be its main driver.
The earliest mammals were exclusively nocturnal, and are thought to have only started venturing out in daylight once the dinosaurs had become extinct. The University of California, Berkeley’s
Kaitlyn M. Gaynor, who led the research, said that humans were just as much of a “terrifying force” as dinosaurs, and were driving mammals “back into the night”. Writing in the journal Science, she and her colleagues warned that the trend could affect some mammals’ eating habits, with
knock-on consequences for other species.