3 min read

Chimpanzees Are Becoming Night Owls. Blame Humans.

Chimpanzees, unlike Brooklynites, aren't typically active after sundown. But in response to increased pressure from humans in Uganda's Kibale National Park, some chimps have adopted the dark in order to find food.

By setting up infrared camera traps near a crop field at the edge of the tropical forest, French and Ugandan researchers could keep track of the chimps' night moves. Large groups of chimpanzees - parties of about eight, rather than the usual groups of three who eat together during the day - would venture into a maize field, swinging over a trench via a fallen tree.

A handful of chimpanzees cross over the trench leading into a maize field during the day. (YouTube/PLOS Media)

And come back, loot in mouth. (YouTube/PLOS Media)

Over 20 days in February 2013, the primatologists spotted 14 raiding parties venturing into the corn fields. The chimpanzees, under cover of darkness, spent twice as long grabbing maize after the sun had gone down than during the daytime.

(YouTube/PLOS Media)

(YouTube/PLOS Media)

It's an unusual behavior, the scientists note, but a reaction to habitat destruction near the park. "Even though the chimpanzees' home range has been seriously damaged and disturbed by both logging activities and significant human demographic pressure, chimpanzees have shown great behavioural flexibility including unexpected nocturnal behaviour," the researchers write in the journal PLOS ONE.