Landscape Attributes Shape Population Density Patterns of Black and Gold Howler Monkeys ( Alouatta caraya ) Across Their Southern Range

Understanding the drivers of spatial variation in primate population attributes is essential, especially in human-modified landscapes. However, most research has focused on assessing the effects of forest patch size on presence-absence data rather than how landscape attributes can shape population density. Numerous studies have presented data on Alouatta caraya (A. caraya) populations across their distribution, revealing variation in population densities among sites. Although there are hypotheses to explain why population density varies, the ecological factors influencing such variation remain poorly understood. We aim to explore the effects of landscape attributes, climatic and ecological variables in A. caraya population density throughout its southern range. We gathered a database of population data of A. caraya, and tested the effects of landscape attributes, land-use, temperature, precipitation, seasonality, elevation, and presence of sympatric species on the population density using generalized linear models. Total forest cover and landscape configuration were the most influential predictors of A. caraya density, while the presence of other species had a low but non-significant effect, and land-use and climatic variables had a weaker or no effect. Overall, howler density increases in landscapes when there is a larger number of patches of forest mixed with a heterogeneous matrix. These results support the assumptions that ecologically flexible species may positively respond to forest fragmentation, highlighting the conservation value that small patches can have for some species. As A. caraya is a forest-dependent species, conservation efforts should prioritize maintaining and enhancing patch connectivity to ensure the long-term persistence of their populations.