The Yellow-tailed woolly monkey (Lagothrix flavicauda) is a rare New World monkey native to Peru. It was first described by Alexander von Humboldt in 1812 based on a skin found 10 years earlier. Humboldt had never seen a live animal of this species and for over 100 years, the Yellow-tailed woolly monkey was reported on only a few isolated occasions, so it was thought to be extinct. In 1926, three Yellow-tailed woolly monkeys were collected in San Martin, and later in 1974, a group of scientists found a young Yellow-tailed woolly monkey that was kept as a pet in the city of Pedro Ruiz Gallo, Amazonas. The rediscovery attracted the attention of national and international press, as well as conservation organizations that saw the need to know quickly the status of this species. Today, the Yellow-tailed woolly monkey is considered one of "The World's 25 Most Endangered Primates".
The Yellow-tailed woolly monkey is one of the rarest Neotropical primates and is one of Peru's largest endemic mammals. The monkey's color is deep mahogany and copper with a whitish patch on its snout extending from the chin to between its eyes. Its fur gets darker towards its upper body, making its head seem almost black. It has a powerful prehensile tail, with a hairless patch on its underside and a yellowish pelage on the last third of the tail, giving this species its name. This coloration of the tail is not seen in infants and juveniles. The powerful tail is capable of supporting the animal's entire body weight while feeding or just hanging around; it also uses its tail to help travel through the canopy. The Yellow-tailed woolly monkey also has a long, yellowish, pubic hair tuft. Their fur is longer and denser than other woolly monkeys, an adaptation to its cold montane forest habitat.
Yellow-tailed woolly monkeys can be found only in the Peruvian Andes, in the departments of Amazonas and San Martin, as well as bordering areas of La Libertad, Huánuco, and Loreto. They live in the montane cloud forests with steep mountain sides and deep river gorges. These cloud forests are located in high altitudes and often have cloud coverage near or in them.
Yellow-tailed woolly monkeys are diurnal animals. They live high up in trees in large social groups of both males and females. These groups may contain up to around 23 individuals. Yellow-tailed woolly monkeys are very skillful climbers and can leap up to 15 m (50 feet) through the air. They express aggressive behaviors upon initial encounters such as branch shaking, "mooning" of the scrotal tuft, and short loud, "puppy-like" bark which they use as a territorial or alarm call. Yellow-tailed woolly monkeys feed early in the morning and in late afternoon and the rest of the time is spent resting, travelling, playing, and grooming. Yellow-tailed woolly monkeys are also known to have an interesting habit called geophagy, the consumption of soil. Geophagy provides Yellow-tailed woolly monkeys with needed minerals that they do not get from their regular diet and it also helps reduce intestinal parasites.
Yellow-tailed woolly monkeys are herbivores primarily frugivorous and eat a wide variety of fruits. However, they can also consume leaves, flowers, buds, and roots, and sometimes insects and other invertebrates.
The Yellow-tailed woolly monkey is one of the least known of the primate species so little is known about its mating system and reproductive behavior. Females give birth to a single infant and have long interbirth intervals.
The major threat to the Yellow-tailed woolly monkey is the loss of its habitat. This happens mainly due to the construction of new roads, fragmentation from agriculture, logging, and cattle ranching. Hunting, together with the monkeys' naturally low population densities, slow maturation, and low reproductive rate adds to their vulnerability to extinction. All this and the restricted geographic distribution of the species have led to its current critically endangered status.
According to the IUCN Red List, the total population size of the Yellow-tailed woolly monkey is around 1,000-10,000 individuals. Currently, this species is classified as Critically Endangered (CR) on the IUCN Red List, and its numbers today are decreasing.
