Data to accompany the paper “Highly variable densities and a decline in critically endangered golden-crowned sifaka (Propithecus tattersalli) population abundance from 2008-2018,” International Journal of Primatology, In review, 2022.
Animal abundance is determined by a number of factors, including vegetation structure, food availability and quality, human activities, predation risk, and disease. Vegetation structure, food availability, and human activity are often used to guide conservation efforts, such as protected area zoning and reforestation, especially for primates. We sought to determine whether Critically Endangered golden-crowned sifaka (Propithecus tattersalli) densities could be predicted across a heterogeneous landscape as a function of vegetation structure, food availability, and human activity. We conducted walking transect surveys across the sifakas’ entire global range in the Loky-Manambato Protected Area of Madagascar from 2016–2018, expanding upon a study conducted in 2006/2008. Potential predictors of sifaka density included metrics of vegetation structure (e.g., tree density, forest type), food availability (e.g., food tree basal area, normalized difference vegetation index (NDVI)), and human activity (e.g., tree cutting, livestock grazing). Low-intensity tree cutting and wet season NDVI were the best, positive predictors of sifaka densities. Our results suggest that from 2008-2018, populations declined by 30-43%, from at least 18,000 (estimated confidence interval of 11,000 – 26,000) to 10,222-12,631 individuals. Sifaka densities within study units across their restricted range (880 km2) were highly variable (range: 6.8-78.1 sifakas/km2), emphasizing the importance of large-scale and randomized study designs for assessing species abundance, regardless of its area of occupancy. Understanding that wet season NDVI was a positive predictor of sifaka densities can aid managers in prioritizing conservation actions in this region using widely available and remotely sensed data.