PERUVIAN YELLOW-TAILED WOOLLY MONKEY

Lagothrix flavicauda

Geographic Distribution and Habitat
The Peruvian yellow-tailed woolly monkey, sometimes simply referred to as the yellow-tailed woolly monkey, has an extremely restricted geographic range and is found only in a small belt of cloud forest in northeastern Peru. It is restricted to high elevation cloud forests of 4,921–8,858 feet (1,500–2,700 m) above sea level and is not found in the lowland Amazonian rain forests.

The species was originally classified as Lagothrix flavicauda, but then changed to Oreonax flavicauda. However, recent work on genetics has found that the original classification of Lagothrix flavicauda is, in fact, the most appropriate for this species.

Size, Weight, and Lifespan
Peruvian yellow-tailed woolly monkeys are one of the largest species of neotropical primates. While physical measurements are not well-documented for this species, there appears to be little visible size difference between males and females, although males tend to be heavier. Both sexes have an average head and body length of around 17.3–20.9 in (44–53 cm) with tails of approximately 23.6–25.6 in (60–65 cm) in length. Males weigh more than females at around 17.6–26.5 lb (8–12 kg), compared to 12.1–17.6 lb (5.5–8 kg) for females.

The lifespan of the species is not known, although similar monkeys live for approximately 25–30 years.

Appearance
Peruvian yellow-tailed woolly monkey are large-bodied primates with a thick, soft, mahogany-colored pelage that is longer and denser than the other woolly monkeys. Their pelage ranges from darker brown around their chests and bellies to more copper-tinged around their backs. Males generally have darker fur on their head and bodies than females. They have dark faces with short white hairs around the mouth and nose, which create a distinctive white “muzzle.”

Adult males have a long and distinctive tuft of golden hair around their genitalia, which measures up to 3.9 in (10 cm) in length. This is also present in females, although it is much shorter. Females can also be identified by their long and prominent clitoris, which may cause non-experts to identify them as male.

With long, prehensile tails that aid in balance and locomotion, Peruvian yellow-tailed woolly monkeys get their name from the distinctive coloration on their tail, the lower third of which is covered in yellow hair on the inner side. However, this yellow coloration develops as the monkey ages and is present only in sub-adult and adult monkeys, not in juveniles or infants.

Photo credit: Platyrrhinus/Creative Commons

What Does It Mean?

Bushmeat:
Meat from wildlife species that are hunted for human consumption, generally in tropical forests.

Diurnal:
Active during daylight hours.

Fission-fusion society:
A society in which the members of a social group break off into smaller groups and then rejoin as a larger group.

Frugivorous:
Having a diet that consists of fruits.

Paternal care:
Paternal care is parental investment provided by a male to his own offspring, such as carrying, providing food, or protection.

Slash-and-burn agriculture:
A method of unsustainable farming where farmers clear land by cutting and burning flora in order to create an empty field—a “swidden”—for cultivation. Such practices are detrimental to local ecosystems.

Subsistence farming:
Small-scale agriculture where farmers grow crops to meet the needs of themselves and their families.

Visit the Glossary for more definitions

Diet
​​Peruvian yellow-tailed woolly monkeys are primarily frugivorous; ripe fruits make up a large part of their diet, especially figs. However, they also eat flowers, as well as other plant matter such as leaves, buds, and roots. They sometimes consume insects and can spend around 30% of the day foraging. While crop-feeding is not as common in South America as in Asia and Africa, this species does sometimes feed on corn, as well as on some other crops grown by farmers within their range.

Behavior and Lifestyle
Diurnal and arboreal, they are active during daytime hours and spend their lives high up in the forest canopy. They favor the middle strata of the trees to travel through the forest and use their long, prehensile tail to aid their balance as they navigate through the trees. They are excellent climbers and can leap an incredible 50 feet (15 m) through the air.

Their days are spent in roughly equal parts resting, foraging, and traveling, with approximately 2% of their day spent in social activities, such as grooming or play. They tend to travel and feed in early morning and late afternoon, and rest around midday when the forest is hottest. Each night they sleep high in the forest canopy where they are safest from predators like pumas.

Daily Life and Group Dynamics 
Peruvian yellow-tailed woolly monkeys live in multi-male, multi-female groups and the average group size tends to be between 14 and 16 individuals, although groups as large as 30 individuals have been sighted by researchers. While they display some amount of fission-fusion social structure, compared to other neotropical primates—such as spider monkeys—they tend to live in quite cohesive groups. The group is spread over a rather small area (197 ft; 60 m) and they do not spend long periods of time separated, although this may vary with habitat and group size.

Quite peaceful monkeys, they do not engage in high amounts of aggressive behavior. Where there is aggression between adult males, it tends to be symbolic, rather than involving physical contact, and expressed in the form of bodily displays. Like many other primates, adults engage in social grooming, although this is primarily in male-female dyads as males rarely groom other males. Juveniles frequently engage in play activity, but this is rare in adults. They share habitat with other primate species, such as the white-bellied spider monkey (Ateles belzebuth), the Peruvian night monkey (Aotus miconax), and the white-fronted capuchin (Cebus albifrons), but little is known of their interactions with other groups of the same, or different, species.

Fun Facts

Males sometimes carry young infants, who cling to their bellies, suggesting some level of paternal investment in this species. 

Adult males are easily identifiable due to a 3.9 in (10 cm) long tuft of yellow hair which covers their genitalia. 

These monkeys spend their days high up in the forest canopy and can leap up to 50 feet (15 m) between branches. 

Communication
Like many other primates, Peruvian yellow-tailed woolly monkeys communicate using a range of modalities, such as vocalizations, gestures, facial expressions, and olfactory communication.

This species probably—like closely-related species of woolly monkeys—produces a variety of vocalizations that can be grouped into contact calls, alarm calls, and vocalizations produced during social interactions. Peruvian yellow-tailed woolly monkeys have been known to emit sharp barks in response to threats, including the presence of unknown humans.

Similar species of woolly monkeys have also been known to chest-rub, a scent-marking activity wherein the monkey rubs glands located on his chest repeatedly along a substrate, such as a branch. This behavior is often displayed by males and is probably used in a reproductive or hierarchical context, although it is not clear if Peruvian yellow-tailed woolly monkeys engage in this behavior.

Reproduction and Family
The Peruvian yellow-tailed woolly monkey lives in multi-male, multi-female groups and therefore females probably mate with more than one male. Their reproductive habits are not well understood, but they probably reproduce only around once every three years. Sadly, this slow life history makes this species more vulnerable to extinction. Females give birth to a single infant and infants have been seen clinging to males as well as females, suggesting some investment of paternal care in this species—although it is unclear if a male is able to identify his own offspring. Individuals probably reach sexual maturity sometime after four years of age, but, again, reliable data are not available for this under-studied species. 

Photo credit: Nick Athanas/Flickr/ShareAlike

Ecological Role
​The Peruvian yellow-tailed woolly monkey is primarily frugivorous, and therefore likely plays an important role in seed dispersal within its home range. While home ranges are thought to be small (0.4–0.6 sq miles; 100–150 ha), this can vary with habitat and so distance of seed dispersal probably varies throughout its range.

Conservation Status and Threats
The Peruvian yellow-tailed woolly monkey is currently classified as Critically Endangered by the International Union for Conservation of Nature (IUCN, 2019) and the overall population is in decline. Sadly, they have been listed multiple times on the World’s 25 Most Endangered Primate Species list by the International Primatological Society in recent years and are one of the most critically endangered primates in the world.

The major threat to this species’ existence comes from deforestation due to an increasing human population within its range. As the whole population of this species is restricted to such a small area, they are at high risk of extinction if this habitat is destroyed, a threat made worse by their relatively slow reproduction rates. The conversion of other areas of agricultural land in Peru to large-scale palm oil and/or rice plantations has forced many small-scale farmers to move higher into the cloud forest habitat of the Peruvian yellow-tailed woolly monkey and led to deforestation and slash-and-burn agriculture. In many areas, the remaining individuals of this population have been left in isolated forest patches, which poses difficulties for reproduction and long-term population viability. Mining also poses an additional threat to this species through habitat destruction and pollution, and by opening up previously undisturbed areas for immigration and hunting.

Despite being illegal, hunting this species for bushmeat and/or the pet trade still occurs throughout its range and its large size makes it an easy and valuable target for hunters. In addition to humans, pumas and large raptors pose a threat to Peruvian yellow-tailed woolly monkeys.

Conservation Efforts
The Peruvian yellow-tailed woolly monkey is currently listed on Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES, 2005), an international agreement between governments whose aim is to ensure that international trade in specimens of wild animals and plants does not threaten their survival—banning their trade in all but exceptional circumstances, although in reality this does not appear to be strictly enforced.

Thanks to the efforts of conservation organizations, more protected areas within this species’ range have been designated in recent years. However, researchers warn that current protected areas are not enough to ensure the long-term protection of the Peruvian yellow-tailed woolly monkey. More protected areas are needed, as well as greater enforcement of existing legislation. Due to the increasing human population within its range, community conservation efforts will be invaluable in protecting this species. Some eco-tourism projects have been launched within this monkey’s range to provide communities with alternative sources of income and to highlight the financial benefits of preserving this species.

Additionally, more research is needed to better understand population size and trends, as well as to better understand this species’ life history and behavior, which will help conservationists suggest more effective conservation actions.

References:

  • ​​DeLuycker, A. M. (2007). Notes on the yellow-tailed woolly monkey (Oreonax flavicauda) and its status in the Protected Forest of Alto Mayo, northern Peru. Primate Conservation, 22(1), 41-47.
  • Di Fiore, A., Chaves, P. B., Cornejo, F. M., Schmitt, C. A., Shanee, S., Cortés-Ortiz, L., … & Pacheco, V. (2015). The rise and fall of a genus: Complete mtDNA genomes shed light on the phylogenetic position of yellow-tailed woolly monkeys, Lagothrix flavicauda, and on the evolutionary history of the family Atelidae (Primates: Platyrrhini). Molecular phylogenetics and evolution, 82, 495-510.
  • León, J. J., Vargas, S. A., Ramírez, M. A., Galvis, N. F., Cifuentes, E. F., & Stevenson, P. R. (2014). Vocal communication in woolly monkeys (Lagothrix lagothricha lugens) in Cueva de los Guacharos National Park, Colombia. In The Woolly Monkey (pp. 187-205). Springer, New York, NY.
  • Luna, M. L. (1980). First field study of the yellow-tailed woolly monkey. Oryx, 15(4), 386-389.
  • Matthews, L. J., & Rosenberger, A. L. (2008). Taxon combinations, parsimony analysis (PAUP*), and the taxonomy of the yellow‐tailed woolly monkey, Lagothrix flavicaudaAmerican Journal of Physical Anthropology, 137(3), 245-255.
  • Schneider, E., Taylor, S., & Garden, L. Z. (2000). Chest-rubbing in Captive Woolly Monkeys. Primates, 41(2), 185-188.
  • Shanee, S. (2011). Distribution survey and threat assessment of the yellow-tailed woolly monkey (Oreonax flavicauda; Humboldt 1812), Northeastern Peru. International Journal of Primatology, 32(3), 691-707.
  • Shanee, S., & Shanee, N. (2011). Activity budget and behavioural patterns of free-ranging yellow-tailed woolly monkeys Oreonax flavicauda (Mammalia: Primates), at La Esperanza, northeastern Peru. Contributions to Zoology, 80(4), 269-277.
  • Shanee, N., & Shanee, S. (2014). Yellow-tailed woolly monkey (Lagothrix flavicauda): Conservation status, anthropogenic threats, and conservation initiatives. In The woolly monkey (pp. 283-299). Springer, New York, NY.
  • www.alltheworldsprimates.org
  • ​http://pin.primate.wisc.edu/factsheets/entry/yellow-tailed_woolly_monkey/behav

Written by Jennifer Botting, PhD, April 2020