New research has shown that many species of mammals are being driven to become nocturnal, by nearby human activity, according to The Guardian.
The study, published in the journal Science, examined 62 species of mammals around the world, revealing that when humans were nearby, they often became less active during daylight hours. The change was even observed in species that were already considered nocturnal.
Scientists warn that beyond the effect this has on individual species, a chain reaction might affect other species in their ecosystems. For example, coyotes in California are now eating nocturnal animals such as mice, rats, and rabbits, instead of diurnal squirrels and birds.
“Humans are now this ubiquitous terrifying force on the planet and we are driving all the other mammals back into the night-time,” according to the study’s first author, Kaitlyn Gaynor, a doctoral student at the University of Berkeley.
She notes that before the extinction of dinosaurs, mammals were generally nocturnal – an adaptation to avoid danger during the day.
Dr. Chris Carbone, of the Zoological Society of London, who was not involved in the new study, commented:
“One of the key, interesting findings here is we are used to seeing human impacts on the environment in terms of loss of habitat or conversion of habitat or loss of space for those big, wide-ranging species – but this is talking about loss of time.”
Carbone and Gaynor both suggest that it may be necessary to limit human activity in some areas. Recent research by Carbone found that hedgehogs are active for more hours of the night in parts of London parks that close at night.
“It is likely that we are going to need to preserve wilderness areas that are entirely free of disturbance to protect really vulnerable species, and for species that can’t shift their activity to the night-time or where increased nocturnal activity is having negative consequences, we may need to restrict human activity to certain times of the day so we leave some daylight hours for animals to do their thing.”
The research examined data for each species from a total of 76 previous studies, using information from motion-activated cameras, human observation, and tracking devices. They found that high levels of human activity, such as hunting, hiking, and construction, was linked to 1.36 times as much nocturnal mammal activity. In 141 measurements from the studies analyzed, 83 percent showed an increase in nocturnal activity.
These changes occurred even in relation to human activities that did not directly threaten the animals. In addition to a fear of humans, the authors cite factors such as light pollution and food availability.
“A lot of the species that are adapted to [daytime] activity may be less successful at finding their food, or avoiding their predators, or finding their mates if they are active more exclusively at night – and this could potentially reduce their survival or their ability to reproduce,” according to Gaynor.