Vertical space use and activity changes with seasonal climate variation in Bengal slow lorises (Nycticebus bengalensis) in Thailand

Abstract Most species are adapted to navigate the seasonal variations that impact their habitat use and behavior. We can use this baseline understanding of their seasonal responses to understand how they may respond to more extreme and unexpected changes. The canopy structure can provide a buffering effect for arboreal species through vertical microclimatic gradients, creating potential microrefugia. In this study we examine how seasonality impacts the activity and vertical space usage of the nocturnal Bengal slow lorises ( Nycticebus bengalensis ) in Northeastern Thailand. We collected behavioral and concurrent climatic data from June 2023 – August 2024 and used Bayesian multinomial logistic models for each season to understand the impact of loris height in the tree, temperature, and relative humidity on behavior. We found that temperature had the strongest negative association with activity levels and verticality across all seasons. When temperatures rose above average, slow loris activity declined, suggesting that the buffering effect of lower canopy layers was limited when temperatures exceeded the thermal neutral zone for this species. The lower canopy is a climate microrefugia for Bengal slow lorises, however it depends on upper canopy connectivity. As global temperatures rise due to climate change, it is essential that we maintain forest canopy structure to preserve these microrefugia, especially for nocturnal species that have no cooler period to utilize.