Explaining the primate extinction crisis: predictors of extinction risk and active threats

Explaining why some species are disproportionately impacted by the extinction crisis is of critical importance for conservation biology as a science and for proactively protecting species that are likely to become threatened in the future. Using the most current data on threat status, population trends, and threat types for 446 primate species, we advance previous research on the determinants of extinction risk by including a wider array of phenotypic traits as predictors, filling gaps in these trait data using multiple imputation, and considering more explicitly the mechanisms that connect organismal traits to extinction risk. Our Bayesian phylogenetically controlled analyses reveal that larger-bodied and insular species exhibit higher threat status, while those that are more omnivorous and live in larger groups have lower threat status. The same traits are not linked to risk when repeating our analyses with older IUCN data, suggesting that the traits that influence species risk are changing as anthropogenic effects continue to transform natural landscapes. We also show that larger-bodied and arboreal species are more susceptible to key threats responsible for primate population declines. Collectively, these results provide new insights to the determinants of primate extinction and identify the mechanisms (i.e., threats) that link traits to risk.