When the wild things are: URI team reports on mammalian daily activity with surprising results

(Press-News.org) KINGSTON, R.I. – Feb. 26, 2025 – Animal antics have captured public attention and viral views across the U.S. in the last few years with the advent of mini cameras that capture the movements of animals in front yards nationwide, from bear to deer.

A University of Rhode Island-based group has taken the camera concept one step further and then some, generating a massive dataset of animal images, not for entertainment, but for science. 

When the Global Animal Diel Activity Project results were analyzed, researchers made some unique discoveries. 

Put together, researchers across the country and around the world generated a more focused picture of animal habits at various times of day. The team created a camera trap dataset from 20,080 camera sites across 38 countries in six continents. They gathered and analyzed data on more than 400 mammal species, representing one of the largest camera trap datasets in existence.

Together, they leveraged 8.9 million observations to create an enormous library of standardized activity estimates, finding that less than half of the estimates for the species studied were in agreement with their diel classifications in common reference literature.

Brian Gerber, a University of Rhode Island research ecologist now with the U.S. Geological Survey at Colorado State University, and Kadambari Devarajan, URI research fellow and affiliate through 2024, led the project team of over 200 collaborators that recently published their findings in Science Advances. Gerber was the project’s principal investigator along with Devarajan, an engineer-turned-ecologist and National Geographic Explorer now based in Mumbai, India.

What’s the diel?

The idea for the study germinated 18 years ago when Gerber was in Madagascar studying the fossa there for his master’s degree, and saw how much variation there was when they were active. Fast forward to 2017 when Gerber, now at URI, determined a methodology to explore the topic of animal diel phenotypes with colleagues elsewhere in the field. 

The project stands out for its scale, scope, and subject matter. The study examined 445 terrestrial animals in total, from American bison to zorillas, using data from cameras in a range of environments, including arid desert, rainforests, arctic tundra, and savanna grasslands.

Gerber was surprised by the variability of when species were active.

“I expected some variation,” he says, “but basically most species that we had adequate data on showed that they would change their diel activity.” For example, American black bears were found to be diurnal and cathemeral — nocturnal and irregularly active during the day and night —  at different places and times. 

The study examined how the general “global human footprint” affects diel activity. Because the researchers were looking at data from both urban and wild locales, they saw some species become more diurnal and others more nocturnal. Overall, a third of species were affected by the human footprint measure.

And how does this relate to the typical front-step or back-deck wildlife observer, perhaps a human “lark,” spotting a raccoon wandering by the front door or sighting a deer across the yard? 

“The most striking thing is that when you are taught an animal is diurnal or is nocturnal, that is not always correct,” says Gerber. “Many terrestrial mammals will be diurnal sometimes and nocturnal or cathemeral other times. When you see a nocturnal species during the day, this is perhaps not as unusual as you might think.”

Species are often classified as diurnal, nocturnal, or crepuscular (twilight) and sometimes cathemeral, as if these are immutable phenotypic traits, adds Devarajan. When an animal is active is certainly impacted by the species' evolution, but it's also a behavioral response to its environment.

The data provided some surprising results, including that much of the existing diel classifications are inaccurate. The team found existing classifications were accurate for only 39% of all species studied. 

Out of the species studied, 74% switched phenotypes. Species that became more nocturnal with increasing global human footprint included urban adapted mammals like the striped skunk, as well the snowshoe hare, gray fox, and North American porcupine. 

While light availability played a role in diel plasticity, the team found that increasing anthropogenic pressure (environmental change caused by people) impacted mammals, primarily in North America.

Animal behavior in focus

Animals’ diel activity is important for better understanding changes in animal distribution and abundance, critical measures that are used to determine species endangerment and legal harvest levels. The team’s results will be useful for organizations and conservation initiatives since it's important to know when species are active in order to better conserve them, especially in the wild.

As the world is experiencing a time of rapid environmental change, says Gerber, many species are shifting their diel phenotypes with unknown fitness consequences. Species that cannot shift or adjust behaviors may experience negative outcomes if their behavior doesn’t change. 

“Recognizing the fitness consequences of species’ diel phenotype plasticity and lack thereof is an important next step to understand the impacts of environmental change and can help direct conservation actions,” Gerber says.

See the searchable library of the team’s results here and watch for a fun video about the project created by the U.S. Geological Survey. 

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