Peruvian Yellow-tailed Woolly Monkey
The Peruvian yellow-tailed woolly monkey is a large Peruvian primate.[1] It lives nowhere else. Its scientific name is Lagothrix flavicauda. It lives in the cloud forests of the northern Peruvian Andes. It counts among the Peruvian monkeys. It is also one of the New World monkeys. The IUCN lists it as Critically Endangered.[2]
This Critically Endangered woolly monkey lives only in Peru's Andean cloud forests.
- Common NamesPeruvian yellow-tailed woolly monkey, yellow-tailed woolly monkey, Hendee's woolly monkey, mono choro de cola amarilla
- Taxonomy Classification Year1812
- Monkey SizeMuseum adults average 53 to 56 cm (21 to 22 in) in head and body; tail 56 to 63 cm (22 to 25 in)
- Skin Color(s)Deep mahogany coat, darker head, white muzzle patch, yellow tail band
- HabitatMontane rain forest and cloud forest, about 1,100 to 2,700 m
- DietMostly fruit, plus leaves, insects, mosses, buds and flowers
- Native CountriesPeru
- Its deep mahogany coat is thick and long for a woolly monkey.
- A yellow band runs under the last half of its tail.
- It lives between about 1,100 and 2,700 m above sea level.
- Mixed groups of 5 to 22 monkeys travel together.
- Scientists feared it was extinct until its rediscovery in 1974.
Peruvian Yellow-tailed Woolly Monkey Distribution
)Peruvian Yellow-tailed Woolly Monkey Guide:
Name and Classification
Alexander von Humboldt named this monkey Simia flavicauda in 1812. He never saw a live one. He worked from flat skins used as saddle covers by mule drivers.[3] He thought it was a howler monkey.
Hendee collected three skins at Puca Tambo in 1926. Oldfield Thomas described them as a new woolly monkey in 1927. In 1963, Jack Fooden showed both names belong to one species.[4] Fooden placed it in the woolly monkey genus Lagothrix.
Some later experts gave it its own genus, Oreonax. Genetic work since 2014 places it back inside Lagothrix. A 2015 study compared whole mitochondrial genomes.[5] It found this monkey is the oldest branch of the genus. It split from the other woolly monkeys about 2.1 million years ago. It has no recognized subspecies.
Lost and Found
After Hendee's 1926 specimens, nothing more was heard of this monkey. For almost 50 years, scientists thought it might be extinct.
In 1974, a small expedition worked near Pedro Ruiz Gallo, Amazonas. The team obtained four skins and three skulls from a hunter. The team also saw a live young male. It was the first living one shown to scientists. The expedition called it Peru's only endemic large mammal.
Mariella Leo Luna then ran the first field study.[6] She watched six groups during the dry season.
Physical Description
The coat is deep mahogany in both sexes. The head, crown and upper back are blackish. The color grows redder toward the lower back and tail. The fur is longer and thicker than in other woolly monkeys.
The face is dark gray. A clear white patch surrounds the mouth. Golden-yellow hairs ring a bare pad under the tail's last half. That yellow band gives the species its name.
Adults also carry a yellow tuft of hair in the genital area. It is dense in males and smaller in females. Young monkeys lack both the yellow band and the tuft.[7]
Its yellow tail band places it among the yellow monkeys. Its mahogany coat also lists it among the brown monkeys.
Size and Weight
It is one of the largest New World primates. Museum males average 56.2 cm (22.1 in) in head and body. That figure comes from only three specimens. Five museum females average 52.9 cm (20.8 in).
The tail is a little longer than the body. It measures 56 to 63 cm (22 to 25 in).
Adult males weigh 8.3 to 10 kg (18.3 to 22 lb). Females weigh about 5.7 kg (12.6 lb). These figures come from a 2013 report.
Similar Species Compared
Its closest living relative is Humboldt's woolly monkey. Some authorities split that species into several woolly monkeys.[8] A 2014 genetic study proposed just two woolly monkey species.[9] The table uses the IUCN's range and status for it.[10] The IUCN lists it as Vulnerable. Its sizes come from a source that adds the Colombian woolly monkey.
Humboldt's woolly monkey has no yellow tail band. Its coat ranges from pale blond to almost black.
The white-bellied spider monkey shares some of its forests in Amazonas. It has a longer tail and a pale belly.[11] It is listed as Endangered.[12]
| Trait | Peruvian yellow-tailed woolly monkey | Humboldt's woolly monkey | White-bellied spider monkey |
|---|---|---|---|
| Scientific name | Lagothrix flavicauda | Lagothrix lagothricha | Ateles belzebuth |
| Range | Peru only, northern Andes | Brazil, Colombia, Ecuador and Peru | Brazil, Colombia, Ecuador, Peru and Venezuela |
| Habitat | Montane and cloud forest, 1,100 to 2,700 m | Lowland and montane rainforest, up to 3,000 m | Lowland and montane forest |
| Coat and key marks | Deep mahogany, white muzzle, yellow tail band | Pale blond to near black, no yellow band | Blackish back, yellowish-white belly and inner limbs |
| Head and body | Museum averages 52.9 to 56.2 cm | Males 46 to 65 cm, females 46 to 58 cm | 46 to 50 cm |
| Tail | 56 to 63 cm | Males 53 to 77 cm, females 62 to 72 cm | 74 to 81 cm |
| Weight | Males 8.3 to 10 kg, females about 5.7 kg | Males about 7 kg, females 5 to 7 kg | Males average 8.3 kg, females 7.9 kg |
| Diet | Fruit 46%, leaves 23%, insects 19% at one site | Fleshy fruit 79%, leaves 11% at one site | Fruit 73 to 92% across studies |
| Group size | 5 to 22 | Studied groups of 17 and 24 | 15 to 30, in small subgroups |
| IUCN status | Critically Endangered (2019 assessment) | Vulnerable (2020 assessment) | Endangered (2019 assessment) |
Range and Distribution
This monkey lives only on the eastern slopes of the Peruvian Andes. Its core range lies in Amazonas and San Martín. Smaller areas lie in La Libertad, Huánuco and Loreto. Its northern edge follows the Marañón River valley. A few groups survive west of the Utcubamba River.
In 2018, surveyors found it in Junín.[13] That record extended its known range over 200 km south. A 2023 study found it at nine sites in Junín.[14] Nearby lowland woolly monkeys were never found alongside it.
Habitat Needs
It lives in primary premontane, montane and cloud forest. It lives from about 1,100 to 2,700 m (3,600 to 8,860 ft). A few records lie just above 1,000 m. It also uses white-sand, bamboo and ridge-top forests.
One survey checked 43 sites between 2007 and 2010.[15] It found the monkey at 35 of them. Every record came from cloud forest rich in fig trees. Its montane rain forest home makes it one of the rainforest monkeys.
Diet and Feeding
It eats fruit, flowers, leaves, lichens and bromeliad leaf bases. It also takes epiphyte roots, bulbs and insects. At La Esperanza, two groups were followed through the seasons. Fruit made up 46.3% of their diet. Leaves made up 23.3% and insects 19.1%. Mosses, buds and flowers made up the rest.
When fruit runs short, they eat more leaves and insects. Figs and Cecropia trees are among their main food plants. This mixed diet makes it one of the omnivorous monkeys.
These monkeys also eat soil. They come down to the ground to do it. Researchers logged 77 soil-eating events at La Esperanza.[16] Most took place in the dry season.
Behavior and Groups
Groups mix males and females. They hold 5 to 22 monkeys. An average group had about three adult males and four adult females. Lone monkeys of both sexes also turn up.
Home ranges cover 92 to 174 ha (227 to 430 acres). Groups travel about 1 km (0.6 mi) a day. At La Esperanza, they spent about 30% of the day feeding.[17] They spent 29% traveling and 26% resting.
When threatened, the lead male puts on a display. He shows his genital tuft and shakes or drops branches. Excited adults give a sharp bark. Leo Luna compared it to a puppy's bark.
Breeding is poorly known in the wild. Copulation was seen only twice in 15 months of study.
Population and Status
The IUCN assessed it as Critically Endangered in 2019. It suspects a decline of over 80% across 50 years. The assessment covers about 1985 to 2030. Habitat loss and hunting drive that decline.
The 2019 assessment estimated 1,000 to 10,000 mature individuals. Densities are low. Abra Patricia holds 0.93 to 2.24 groups per square km.
Local protection may help. A community project at La Esperanza began in 2007.[18] Surveys there found 9.26 monkeys per square km in 2008/09. They found 14.45 per square km in 2012/13. That rise was not statistically significant. Juvenile and infant numbers did rise significantly.
Major Threats
Rugged terrain protected its forests until the 1950s. Then roads, logging and settlers arrived. Mining has grown in its mountains more recently.
About 11,240 square km of suitable forest remained in 1981. Only 6,302 square km remained by 2008. About 70% of that forest was unprotected.
Hunters kill these monkeys for meat. Farmers kill them for raiding crops. Hunters who shoot a mother often keep her infant as a pet.
Conservation Efforts
It lives in several protected areas. They include Río Abiseo National Park and Alto Mayo Protection Forest. Cordillera de Colán National Sanctuary protects it too. Private and community conservation areas add more cover.
It is listed on CITES Appendix I. The US lists it as endangered under its Endangered Species Act.[19] Peru classes it as Critically Endangered.
In 2007, Neotropical Primate Conservation began a range-wide project. The group works with local communities on research and forest protection. It also runs awareness work and supports sustainable local products.
It appeared on the 2023 to 2025 most endangered primates list.[20]
Cloud Forest Neighbors
The Andean night monkey shares some of its cloud forests.[21] Both live in Río Abiseo National Park.
The Rio Mayo titi lives lower, in the upper Río Mayo valley.[22]
In Huánuco, the Peruvian spider monkey lives along the upper Río Huallaga.[23]
Explore more monkeys starting with P. Or browse all types of monkeys.
Common Questions
It lives only in Peru. It inhabits Andean cloud forests, mainly in Amazonas and San Martín.
Golden-yellow hair runs under the last half of its tail. It lives only in Peru.
Yes. The IUCN lists it as Critically Endangered. Habitat loss and hunting are the main threats.
The 2019 IUCN assessment estimated 1,000 to 10,000 mature individuals.
It eats mostly fruit. It also eats leaves, insects, mosses, buds and flowers.
Adult males weigh 8.3 to 10 kg. Females weigh about 5.7 kg.
Yes. It went unseen by scientists for almost 50 years. An expedition found it again in 1974.
Cite this page
BioExplorer. (2026, November 2). Peruvian Yellow-tailed Woolly Monkey. https://www.bioexplorer.net/animals/mammals/monkeys/peruvian-yellow-tailed-woolly-monkey/
About the author
Wildlife Writer and Photographer, BioExplorer.net
Arjun is a science writer and wildlife photographer at BioExplorer.net. He turns new research on animals into clear, accurate reads for curious readers. His work covers animal behavior, ecology, and newly described species. He holds a Cornell Lab of Ornithology certificate in bird biology. He is pursuing an HBSc at the University of Toronto Mississauga.