Mammals are turning to the darkness of the night for safety, as they try to avoid contact with people.
Researchers have concluded that mammals may now be 1.36 times more nocturnal – active during night – on average because of human disturbance, compared to their known behavioural patterns. Researcher Kaityln Gaynor of the University of California at Berkeley, United States, and her colleagues compiled data from 76 research studies of 62 mammal species, including spotted hyenas in rural, residential South Africa, black bears in Canadian forests that hikers frequent, and leopards in western Maharashtra farm land. Their effort was to see whether increasing nocturnal activity was a global phenomenon among animals that are active during the day, active at twilight or nocturnal.
“When we pooled these cases together, the result was powerful and striking: human activity is creating a more nocturnal natural world,” wrote Ms. Gaynor, lead author of the study published in Science , in an email. The pattern was consistent across six continents, species, habitats and human disturbances, ranging from hiking to road building.
Yet, animals that are active during the day – a pattern developed over millions of years of evolution – may not be successful at finding food, avoiding predators or communicating in the dark. Managers of habitats where threatened species dwell could consider restricting human activity to certain times of the day, wrote Ms. Gaynor.
Time zoning is crucial, because about 25 million kilometres of new roads are likely to be built in India by 2050, said Sanjay Gubbi, member, Karnataka State Wildlife Board.
However, while interpreting such studies, the diverse situations and cultural contexts should be considered, Vidya Athreya, a Wildlife Conservation Society-India scientist said.
