The Density of Callicebus coimbrai is Better Predicted by Vegetation Structure Variables than by Surrounding Landscape

Primate population density often varies considerably between sites, reflecting differences in site conditions and resource availability. Understanding these differences may provide important insights for habitat management. We identified environmental variables that affect the population density of Callicebus coimbrai in forest patches throughout its geographic distribution in northeastern Brazil. We sampled the vegetation structure of 19 forest patches and assessed the composition of the surrounding landscape and the resistance of the surrounding matrix to the movement of C. coimbrai . We used the number of responses of C. coimbrai to playback to estimate the species density in each patch. The density of C. coimbrai was positively related to understory vegetation density, and tree diameter and density, but not to the surrounding landscape composition. The sites with the highest densities were concentrated in the center of the species geographic range and only one of the forest patches may be large enough to host a viable population of C. coimbrai over the long term. Denser understories and larger and closed-spaced trees were related to food availability, and possibly also to predator avoidance, although most predators were extirpated from the region. C. coimbrai tolerate and may even benefit from forest disturbance, depending on how the process has changed the vegetation structure. Our results emphasize the need to enhance the connectivity of the forest patches, particularly in the central portion of the species distribution. Our findings suggest that a whole-range approach is effective to identify the drivers of species density, and priority areas and conservation strategies.