Forest Cover and Altitude Are Key to the Occurrence of Black-Fronted Titi Monkeys (Callicebus nigrifrons) in the Brazilian Atlantic Forest.

Human activities are major threats to biodiversity, particularly for arboreal, forest-specialist species such as platyrrhine primates. Habitat loss and declines in vegetation quality negatively affect species' persistence in disturbed and human-modified landscapes. In this study, we evaluated the influence of landscape structure (forest cover and functional connectivity), vegetation quality and structure (EVI and canopy height), fire disturbance history (% burned area), and altitude on the occurrence of black-fronted titi monkeys (Callicebus nigrifrons) in the Cantareira-Mantiqueira Corridor, a region within the Atlantic Forest biodiversity hotspot. We conducted playback surveys at 72 sites to detect the presence of the species. Using model selection approaches, we assessed the relative importance of environmental predictors on the species' occurrence. The best-supported model included forest cover (within a 250 m radius) and altitude, indicating that greater forest cover at higher elevations best explains the presence of black-fronted titi monkeys. Variables related to functional connectivity, vegetation quality and structure and fire disturbance history had secondary importance. Our findings underscore the critical importance of preserving and restoring forested areas, particularly mid-elevation ranges (500-1200 m). These regions face the most severe degradation, posing a significant threat to black-fronted titi monkeys, a species currently listed as Near Threatened on the IUCN Red List. Our results align with previous studies showing positive associations between forest cover and the occurrence of congeneric species, reinforcing the urgent need for targeted conservation actions in increasingly degraded habitats.