Hidden cameras have caught wild chimpanzees in the act as they carried out night-time raids on farmland.

The new footage, taken by researchers from the Museum of Natural History in Paris and the Uganda Wildlife Authority, shows the chimps adapting to human pressure on their habitat, according to a report by the BBC.

The team says this is the first record of "frequent and risky" nocturnal raids to look for food.

The researchers carried out their study in Kibale National Park in Uganda, by setting up camera traps on the edge of the park.

"[It's] surrounded on the outside by smallholder farms, forest fragments and tea estates," the researchers said in their paper, published in the journal PLOS ONE.

During the 20-day study, researchers were able to record a total of 14 crop-raiding events, with groups of about eight chimpanzees taking part in each raid. Groups of about eight chimpanzees took part in each raid, according to the paper.

Groups included vulnerable animals, such as females with clinging infants. They would raid during the day as well, but during night-time raids the chimps stayed longer in the maize fields.

They showed fewer signs of vigilance and anxiety like looking around or scratching themselves roughly, both recognized as signals of stress.

The raids were far more daring than researchers anticipated and are most likely driven by habitat loss, a bigger threat to the chimps than natural predators.

"It forces chimps to explore new food sources, like human crops," Dr. Catherine Hobaiter, an expert in chimp behavior from the University of St Andrews, told BBC News.

"Raiding fields is extremely dangerous - chimps may be attacked or even killed by people defending their crops, but by raiding at night [these chimps] seem to have reduced this threat," Hobaiter added.

Though the change in behavior is effective, such drastic measures are worrisome to scientists. Hobaiter said that the fact that these animals are willing to go to such lengths to get food means they're under real environmental pressures.

It also increases the chances that there will be run-ins with humans who want to protect their crops..

"From a conservation perspective, the only long-term solution is the protection of the remaining forests," she added.

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