During my thesis project, I studied how squirrel monkeys (Saimiri oerstedii oerstedii) choose their sleeping sites in a Costa Rican landscape heavily influenced by human presence. Sleeping sites are essential for survival: they must provide safety during the night while also allowing efficient access to food resources.
I compared regularly used sleeping sites, occasionally used sleeping sites, and potentially suitable but never used trees to understand what factors really influenced the choice. The results show that there is no single simple explanation.
On the one hand, the presence of humans and dogs seems to play an important role: the most frequently used sleeping sites are more often found in areas with greater human activity. This suggests that monkeys may indirectly exploit human presence as a form of protection against natural predators. Sites used only occasionally, on the other hand, are more frequently found in areas with less human disturbance, where the risk of predation may be higher. Contrary to my expectations, proximity to the first food source in the morning was not a determining factor. Permanent sleeping sites are not necessarily the closest to foraging areas, indicating that safety may be more important than energy efficiency. Tree characteristics also play a role, but not always in the expected way: taller trees with larger trunks are not automatically the most used.
Overall, the results suggest that the choice of sleeping site is the result of a trade-off between safety and access to resources. In a human-modified environment, squirrel monkeys seem to adapt their strategies by combining natural and anthropogenic factors, demonstrating remarkable behavioral flexibility. This highlights how complex the dynamics between wildlife and human presence are and how important they are to consider in future conservation strategies.
