When I first got the call from biologist Sean McHugh with the Rainforest Partnership, I almost did not believe it: yellow-tailed woolly monkeys had been found in the Peruvian Región Junín, more than 200 km south of their known range. I wanted to believe it, but I had my doubts. When Sean sent me a video to confirm the sighting, I half expected to see lowland woolly monkeys, which I had studied for several years in Ecuador. These primates can live at high elevations, and in the shadow of a backlit canopy they could easily be mistaken for their Critically Endangered sister species. But when the video started to play, there it was: the whitish muzzle, the beautiful mahogany fur, and the distinctive yellow scrotal tuft. Only one thing was missing: the eponymous yellow tail.

It was at that moment that I knew this was something exciting. Not only did we have a previously unknown population of a Critically Endangered primate, but it appears to be distinct in its markings as well as geographically removed from other known populations.

The yellow-tailed woolly monkey is an intriguing species. Once thought to be extinct in the wild, in 1974 Russ Mittermeier shocked the primatology world with its rediscovery (although locals had known they were still around), published here in Oryx. After Mariella Leo Luna’s pioneering behavioural research in the 1980s, however, the yellow-tailed woolly monkey sank from academic view and from conservation efforts because of Sendero Luminoso terrorist attacks in the highlands of Peru.

A new era of study on the yellow-tailed woolly monkey began in the mid-2000s, fostered in part by new surveys conducted by Anneke DeLuycker, followed by the work of the UK-based non-profit Neotropical Primate Conservation and the tireless efforts of Peruvian primatologist Fanny Cornejo, the founder of Yunkawasi Peru, who is currently working with Rainforest Partnership and finishing her PhD at Stony Brook University. Their work established long-term study sites in Región Amazonas: one in Yambrasbamba, and another currently ongoing with the community of Corosha, organized as the Asociación de Conservación Oso Dorado de Hierba Buena Allpayacu. This has greatly increased our knowledge of yellow-tailed woolly monkey behaviour and ecology while also establishing strategies for preserving those populations.

This research largely focused on the montane forests between the Marañon and Huallaga Rivers, to which this remarkable primate has long been thought to be endemic. Only in the past five years have research groups lead by Rolando Aquino, among others, published reports of populations outside this area. Their work has pushed the known range both east beyond the Huallaga River, and well south of the previously known range, into Region Huánuco. Our discovery with Rainforest Partnership, however, has pushed the boundary for this species nearly twice as far, opening up the exciting possibility of finding populations for further survey work and conservation efforts.

What should we do now that we have discovered this seemingly unique population?  In collaboration with Fanny Cornejo and Rainforest Partnership, we’ve already begun community-based conservation initiatives to protect this new-found population, funded by the Holloman Price Foundation, Margot Marsh Biodiversity Foundation and the family of Paul Pittman. We have also begun the process of studying exactly how this southern-most population is distinct from other yellow-tailed woolly monkeys. This past summer, MSc student Melissa Zarate—funded by the National Science Foundation Graduate Research Fellowship Program, Margot Marsh Biodiversity Foundation, Primate Conservation, Inc., and the American Society of Primatologists— collected faecal samples from many populations of  the yellow-tailed woolly monkey in Peru including in Corosha, Yambrasbamba and Junín. Over the next few months, she will genotype these samples to assess how isolated the Junín population is, relative to those further north.

All of this work—the search for previously unknown populations, novel and community-based conservation initiatives, and the use of behavioural and genetic data to determine population status and viability—increases our knowledge of this beautiful and rare primate. With this new population, we have renewed hope to protect the yellow-tailed woolly monkey for future generations.

All photos: Jasmina McKibben

The article First record of the Peruvian yellow-tailed woolly monkey Lagothrix flavicauda in the Región Junín, Peru is available in Oryx—The International Journal of Conservation.

Christopher A. Schmitt is Assistant Professor of Anthropology and Biology at Boston University, where he is also co-director of the Sensory Morphology and Genomic Anthropology Lab. He conducted his dissertation research on lowland woolly monkeys in Amazonian Ecuador, and has also studied the genomics of obesity in other primates. He is an affiliated Research Scientist with conservation NGO Rainforest Partnership in the USA.