Arboreal camera trapping reveals diel-vertical migrations in arboreal wildlife of the Peruvian Amazon rainforest

Tropical forests harbor much of Earth’s biodiversity, with the ground to emergent canopy forming dynamic three-dimensional habitats. Arboreal and semi-arboreal species navigate the vertically heterogeneous environment, in temperature, light, predation risk, and resource availability, responding to further diel, lunar, and seasonal changes. While diel vertical migrations are well studied in aquatic systems, similar patterns in arboreal mammals and birds remain unclear. The roles of unique species vertical shifts in time in structuring tropical forest assemblages, the interaction of vertical stratification and temporal niche partitioning, is poorly understood. We investigate diel vertical behaviors in 31 species of arboreal mammals and birds in the Madre de Dios region of Peru using ground and canopy camera trapping surveys. We assess diel-vertical overlaps among sympatric species and examine relationships between dietary traits and vertical preference and selectivity. Our results reveal many unique patterns of vertical shifts, with many Primates and couple of Cracids descending from crepuscular canopy activity to lower strata at midday, while Tamandua tetradactyla descends from sunrise to sunset and Choloepus hoffmanni from before to after midnight. Lagothrix lagothricha and Pithecia spp. displayed peaks in upper canopy activity at midday, possibly due to ecological release from other primates. We find high diel-vertical overlap between sympatric species pairs, suggesting niche partitioning may involve finer-scale spatial and temporal adjustments rather than strict vertical segregation. We also find patterns of lunar cycle-related shifts in vertical activity for Tamandua tertradactyla, Choloepus hoffmanii and Aotus nigriceps . Diet-related patterns in mammals indicate carnivores favor lower heights, frugivores prefer higher strata, and invertivores are more vertically variable. These findings challenge static views of vertical stratification, emphasizing the need for a framework integrating temporal and spatial variability in the vertical environment and its many biotic agents. Better understanding these vertical dynamics may be valuable for predicting arboreal species and community responses in their warming, fragmenting and increasingly peri-urban habitats.