Animal hooligan after dark

When it comes to daily schedules, wild animals do not follow the rulebook. New research shows that many mammals do not adhere to strict daytime or nocturnal organisms, especially in areas where humans are increasingly present.

A groundbreaking global study analyses nearly 9 million camera trap images in 38 countries and found that long-term scientific assumptions about when animals are active may require extensive revision.

The study, published in Science Advances, compiled data on 445 species and found that over the entire 24-hour cycle, less than half of the traditional classifications matched daytime activity (daily and night), nocturnal activity (nocturnal), twilight (nocturnal activity), or irregular activity.

“Our arguments are based primarily on anecdotal evidence, but the research project does quantify that wildlife species are not particularly suitable for these parameters, and that our changing environment affects their activities.”

Perotto contributed data from his research in the Edwards Plateau area, where the camera trap was originally designed to study the Rio Grande wild turkey, capturing a lot of information about other wildlife passing through the area.

The international team found that of 445 species, only 39% matched their established patterns of activity in the scientific literature. Many activities regularly switch different periods of activity.

“The most striking thing is that when you are taught that animals are day-night, or nocturnal, which isn’t always right,” said Brian Gerber, a former research ecologist and co-author of the project. “Many terrestrial mammals sometimes are day-night, night-night, or other times of the catheter. When you see nocturnal species during the day, this may not be as unusual as you think.”

Animals can affect several factors when they are active, including body size, geographical location, and especially the presence of humans. Researchers have observed that mammals in North America are becoming increasingly taller in areas with higher human development.

“When we humans develop land and occupy wildlife habitats, this land use change leads to new behaviors of wildlife,” Perotto explained.

These behavioral changes are not without consequences. Animals forced to change their active time may have difficulty finding food, avoiding predators or successfully reproduction.

The study found that smaller mammals are more likely to become nocturnal on a global scale. Species with a larger geographical range show greater flexibility in their activity patterns, switching between day and night depending on local conditions.

The available daylight has the greatest impact on activity timing, and as daylight changes, many species adjust their schedules seasonally. However, the distance between human footprints and the equator also causes a significant change in behavior.

The research team used data from 200 camera trap projects on six continents, representing more than 10,000 years of camera surveillance. A&M contributions in Texas come from about 56 camera traps that were originally designed to study wild turkeys but captured data from many other species.

This extensive collection of standardized data allows scientists to conduct the first global comparative analysis of the daily rhythms of mammals, revealing nuances that are undetectable by smaller localized studies.

“Further research is needed to better understand these implications and identify ways to mitigate potential negative effects,” Perotto said. “Study like this is advancing science and helping us understand how the ever-changing world affects the rhythm of the natural world.”

The results show that wildlife management and conservation efforts need to consider the flexibility of animal behavior rather than relying on rigid categories of expected animal activity.

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