Population Viability and Genetic Structure of the Last Remaining Population of the Critically Endangered Gray Snub-Nosed Monkey (Rhinopithecus brelichi)

Habitat destruction, land conversion, and forest fragmentation over the past several decades have resulted in major declines and local extirpation of wild animal and plant species. The gray snub-nosed monkey (Rhinopithecus brelichi) is currently listed among the 25 most endangered primate species in the world, with an estimated remaining wild population of less than 400 individuals. Given the potential negative effects of small population size on genetic diversity, we investigated how factors, such as climate, inbreeding, kinship, population structure, and effective population size, have contributed to their genetic status. We extracted DNA from 307 fecal samples and analyzed microsatellite diversity, sex-identifying genes, and the mtDNA control region in 179 wild individuals. Our analyses suggest that gray snub-nosed monkeys experienced an initial population decline during the Last Glacial Maximum, some 20,000 years ago. During the past 70 years, this species experienced a second, steeper population decline, coinciding with human activities. Their current effective population size (± SD) of 675 ± 292 exceeds the remaining number of individuals in the population and has declined by 93.9%—96.7% over the past 20,000 years. Our findings highlight the need for immediate conservation and management strategies to protect this endemic and Critically Endangered primate species.