Researchers from Wildlife Conservation Society (WCS) and the Nature Conservation Foundation spotted and photographed the animals, formally known as Macaca munzala ("deep-forest monkey" in the language of the local people), on a series of expeditions in 2003 and 2004. "This new species comes from a biologically rich area that is perhaps India's last unknown frontier, says team member M. D. Madhusudan of the WCS. The discovery of a new species of monkey is quite rare. What is also remarkable about our discovery is that few would have thought that with over a billion people and retreating wildlands, a new large mammal species would ever be found in India, of all places. The creatures are relatively large, but have shorter tails than other primates of their size. In addition, living between 1,600 and 3,500 meters above sea level makes them one of the highest-altitude primates in the world.
There are 20 other species of macaque monkeys, which live in a variety of locales. The scientists are not sure how widespread the Arunachal macaque is, but plan to undertake future studies to determine its range and whether or not it warrants protected status. A paper describing the animal will appear in a forthcoming issue of the Journal of Primatology.