许多动物在夜间保持清醒以躲避人类

Lions, tigers and other mammals are staying awake at night to avoid human beings, a new study finds.

Scientists have long known that human activity can lead to changes in nature. Many mammals may move around less or travel to distant places to avoid contact with people. By being awake at night, mammals can also be on guard against possible attackers and spend less time looking for food.

The latest research found even activities like hiking and camping can frighten animals and cause them to become more active at night.

Kaitlyn Gaynor of the University of California, Berkeley led the study. She said, "It suggests that animals might be playing it safe around people. We may think that we leave no trace when we're just hiking in the woods, but our mere presence can have lasting consequences."

She and her team of researchers examined 76 other studies involving 62 species on six continents. Among the animals studied were lions in Tanzania, tigers in Nepal, and otters in Brazil.

Researchers compared how much time those animals were active at night in areas of human activity, such as hunting, hiking and farming. The team found that, on average, human presence caused an increase of about 20 percent in night time activity, even in creatures that usually sleep at night.

Results were published in the journal Science.

The findings are unusual because no one else has gathered all this information and looked at it in such detail, noted Ana Benitez Lopez of Radboud University in the Netherlands. She examined the research, but was not part of the study.

Ecologist Marlee Tucker was surprised that any kind of human activity is enough for mammals to see people as a threat.

"It's a little bit scary," she said.

Tucker works at the Goethe University Frankfurt in Germany. She was not part of the study.

Kaitlyn Gaynor said the change in hours will affect animals that have already have trouble in the darkness. But she said that the changes could also help other animals reduce conflict with people.

"Humans can do their thing during the day; wildlife can do their thing at night," she said.

Gaynor added, that way, people would be sharing the planet with many other species.

I'm Jonathan Evans.

The Associated Press reported this story. Susan Shand adapted the report for VOA Learning English. George Grow was the editor.