More than two million photos provide important insight into mammal behavior

We are active in the day and sleepy at night. Daylight is favored while darkness is limited. Animals have to balance their use of time to find food, avoid predators, socialize and stay warm without overheating.

In a new study in Nature Communications, an international team of researchers looked at how different animals use their day.

The idea is that the faunas of different tropical regions are different. There are no animals in the tropics of the Americas, Africa or Asia. The history of species exchange, isolation and evolution within each region is what led to this.

Each region has a range of species of different sizes that feed on plants, insects and other animals, which may be hidden within the differences. If we look at how animals use time, how deep are similarities? Is it possible that coexisting species result in the same tendencies to prefer day or night time activity?

There are more than two million photos.

Our eyes in the forest allow us to see when animals are active. Thanks to the more than 2.3 million pictures collected by the Tropical Ecology Assessment and Monitoring Network, we studied the activity of mammals in 16 protected areas.

We looked at the time when 166 species were recorded to see if feeding needs and size had an effect on each species' activity. We compared the patterns on different continents.

The activity is consistent.

The study showed that the activity of tropical mammals varies based on their size and feeding needs. Smaller species are less likely to be active during the night than large ones. The increase of nocturnal activity correlated with an increase of body size.

Large carnivores and omnivores are more likely to be active during the day than smaller species. The key factor in shaping activity is interaction.

In the Americas, larger insects were more likely to be active in the day while in Africa and Asia they were less likely to be active. The behavior of neotropical insectivores is not clear but they have different needs. The long evolutionary isolation of the South American continent is believed to be the reason for this.

The researchers found that the prey and predator's behavior influenced each other. Top-predators follow activity patterns. This affects other species as well.

It's important to know how natural and near-natural communities interact so that we can explore such patterns in less pristine places. We don't know much about the impacts of human activities such as hunting or the presence of artificial light in places where certain species are rare or absent. Future research will look at such explorations.

There are consistent diel activity patterns of forest mammals in the tropics.

Journal information: Nature Communications