Where Do Monkeys Sleep?

Thermal Drone Images Reveal Insights into Japanese Macaque Sleeping Behavior

Little is known about where and how Japanese macaques sleep. In the morning, the animals are observed descending from trees – suggesting they rest in the canopy. Whether they sleep in groups, on different levels of the same tree, or individually per tree, however, remained unclear.

As part of the Smart Monkey Lab, the SIENA research group at the Carinthia University of Applied Sciences conducted night-time drone flights to collect thermal image data. In parallel, researchers from the University of Vienna confirmed through ground surveys that no animals were present on the forest floor. Analysis of the thermal imagery confirms: the macaques indeed roost at considerable heights in the trees.

Notably, the distribution of heat signatures provides further insight: pixel clusters of elevated temperature vary in size, and the number of clusters is lower than the total number of animals. This suggests that at least some Japanese macaques sleep in groups.

A detailed study on methodology and results is currently being prepared for publication. An update will follow upon release.

The Smart Monkey Lab project is funded by the Austrian Research Promotion Agency (FFG) as part of the BRIDGE program (project no. 4639393, duration 2023-2026).