The Yellow-tailed woolly monkeys are easily recognizable primates due to their long, dark, reddish-brown coat as well as white ring of fur around their mouth. However, the most conspicuous feature of this species is the small, yellow colored strip on the underside of their tail, giving these animals their name. These monkeys have a prehensile tail, which can grip objects. The Yellow-tailed woolly monkeys were originally discovered in the early 19th century. Over time, however, they were believed to have gone extinct. And finally, in 1974, this species was discovered again.
The tiny natural range of this species covers parts of Peruvian Andes, namely, the Department of San Martín in the east and Amazonas in the west. Within this territory, the Yellow-tailed woolly monkeys inhabit 20–25 meters-high canopy of montane cloud forests, most commonly found in rough areas such as steep mountain slopes or deep gorges along rivers.
The Yellow-tailed woolly monkeys are tree-dwelling primates that are active during the daylight hours. They are highly social animals, gathering in groups of 4 - 30 individuals, consisting of a single alpha male, multiple mature individuals of both genders, infants and juveniles. Meanwhile, community size varies greatly among seasons, depending on the availability of suitable food. Small groups occasionally form larger aggregations during periods of abundant food. Group members don't appear to engage in competition. Each group maintains its own, large territory to be able to find sufficient amount of food. Communication between conspecifics is generally performed through vocalizations such as the loud, puppy-like barking call, which is commonly used as an alarm call or a territorial display.
Yellow-tailed woolly monkeys are herbivores and generally feed upon leaves, fruits and flowers. These primates are also known to consume buds, petioles and roots of epiphytes.
This species currently faces a number of quite serious threats. For example, they suffer from continuous hunting. Throughout their tiny range, the small population of these animals is threatened by loss and fragmentation of their natural habitat as a result of human activities such as road development and logging. Some parts of their range are turned into agricultural land. And finally, Yellow-tailed woolly monkeys are threatened by growing human population without their range.
According to the Wikipedia resource, the last estimated population count of the Yellow-tailed woolly monkeys revealed a total population of less than 250 individuals. Currently, this species is classified as Critically Endangered (CR) and its numbers continue to decrease.