- A new study examines when and why mammals eat, sleep and move about, using 2.3 million camera trap photos from the Neotropics, Afrotropics, and Indo-Malayan tropics.
- The researchers found consistent patterns of daily activity across continents, with large carnivores and omnivores being more active during the day and larger herbivores being nocturnal. The main determining factors of daily activity were body size and diet.
- Insectivores were the exception, with larger species being more active during the day in the Americas, but more active at night in Africa and Asia. The activity patterns of carnivores match the activity patterns of their prey.
- The study results have important implications for conservation, the authors say: Knowing when and why different animals in a community are active is fundamental for protecting them, and can also help to mitigate conflicts between humans and animals.
When do weasels sleep? Where do the wild pigs roam? And do jaguars keep their prey up at night?
A new study published in the journal Nature Communications examines when and why mammals eat, sleep and move about, using 2.3 million camera trap photos from the Neotropics, Afrotropics, and Indo-Malayan tropics.
The team found surprisingly consistent patterns of daily activity across the globe. In all of these regions, large carnivores and omnivores (animals that eat both meat and plants) were more likely to be active during the day, while larger herbivores (plant eaters) were more likely to be nocturnal.
“You would think there would be some variation between ecosystems as far apart as Africa and South America,” study lead author Andrea F. Vallejo-Vargas, a Ph.D. candidate at the Norwegian University of Life Sciences, said in a press release. But there was surprisingly little. “Think of it as parallel evolutionary or ecological processes happening across the world at the same time, yielding the same results over and over.”
Insectivores were the exception, with larger species being more active during the day in the Americas, but more active at night in Africa and Asia. The activity patterns of carnivores, particularly top predators, were found to match the activity patterns of their prey, with small prey mostly trying to avoid predators.
Mammal activity patterns were consistent across continents and determined by body size and diet. The researchers suggest there’s a link between body size and thermoregulation constraints, meaning large animals require more energy to maintain optimal body temperature in warm climates. Thus, larger herbivores may be more active at night, when it’s cooler, to save energy.
“The main determining factors of daily activity were body size and diet,” Vallejo-Vargas said.
They also found that the activity of animals that eat plants and insects is largely determined by the climate, while the behavior of predators is largely influenced by the behavior of their prey.
For the study, the researchers used photos of 166 species, including gorillas, wild pigs, African buffalo, jaguars, weasels, and tigers. Many of these species are endangered and understudied.
“This is a great example of how much more information can be gathered from camera trap surveys if they are done across a broad enough scale, and if we look beyond simple species-location data,” Andy Whitworth, director of Costa Rica-based NGO Osa Conservation, who was not involved in the study, told Mongabay.
The data for the study were collected by the Tropical Ecology Assessment and Monitoring (TEAM) Network, which consists of a large group of research partners monitoring biodiversity in protected areas of tropical forests. The initiative was created to establish an early-warning system for tropical forests and to better understand how forests and wildlife are responding to changes at local, regional, and global scales.
“This is an excellent example of the power of large data sets in which the data are collected in a standardized way across sites to inform us about ecological similarities and differences between continents,” Tremaine Gregory, a conservation biologist at the Smithsonian’s National Zoo & Conservation Biology Institute, who was not involved in the research, told Mongabay. “The results are fascinating and have the power to influence conservation and management decisions along with our understanding of basic natural history.”
The study results have important implications for conservation, the authors say. Knowing when and why different animals in a community are active is fundamental for protecting them. Understanding these patterns can also help to mitigate conflicts between humans and animals and to better protect both animals and their habitats.