COMMON WOOLLY MONKEY
Geographic Distribution and Habitat
Occupying the lush forests of the Amazon lowlands in Brazil, Peru, Colombia, Ecuador, and possibly parts of Venezuela, the common woolly monkey (Lagothrix lagothricha), also known as Humboldt’s woolly monkey, is a large, charismatic New World primate. They inhabit several different types of forests, including tropical lowland rainforests, cloud forests, and seasonally flooded forests. They prefer to live in primary rainforests that have remained relatively undisturbed from activities such as logging and agriculture, which often have a full canopy, several layers of understory, and a relatively clear forest floor. Secondary forests, which are formed when a forest is disturbed (such as through selective logging, slash-and-burn agriculture, or forest fire), have a less developed canopy, smaller trees, more vegetation on the forest floor, and less diversity than a primary forest. While common woolly monkeys may sometimes be able to survive in disturbed habitats, they do not thrive in them, so undisturbed primary forest is a necessity for their long-term survival as a species. They typically live at elevations between 3,300 to 8,200 feet (1,000–2,500 m) above sea level.
There are two main subspecies within the species: the red woolly monkey or Poeppig’s woolly monkey (Lagothrix lagothricha ssp. poeppigii) and the Geoffroy’s woolly monkey or Peruvian woolly monkey (Lagothrix lagothricha ssp. cana). Red woolly monkeys are found in western Brazil, eastern Ecuador, and northeastern Peru. Geoffroy’s woolly monkeys are found in Brazil and Peru, with an isolated population in Bolivia. This Bolivian population lives at lower elevations than other woolly monkeys, at about 2,300 feet (700 m) above sea level.
Woolly monkeys, along with spider monkeys and muriquis, are part of the subfamily Atelinae. This group is collectively known as “the atelines” and all share a defining evolutionary characteristic: their long prehensile tails. The taxonomy of the woolly monkey genus (Lagothrix) has long been a subject of debate, with regular revisions to the classifications being published and discussed. As of December 2022, the International Union for the Conservation of Nature (IUCN) holds that there are two species within Lagothrix: the Peruvian yellow-tailed woolly monkey (L. flavicauda), and the common woolly monkey. Other woolly monkey classifications, such as red woolly monkeys (Lagothrix lagothricha ssp. poeppigii) and Geoffroy’s woolly monkeys (Lagothrix lagothricha ssp. cana), are considered by the IUCN as subspecies of the common woolly monkey. There is also another potential subspecies of the common woolly monkey, the Tschudi’s woolly monkey (Lagothrix lagothricha ssp. tschudii), although very little is known about this subspecies. Naturally, these classifications in no way change anything about the biology of these animals, only how they are referred to by people.
Size, Weight, and Lifespan
Common woolly monkeys are one of the largest New World primates by weight. Females weigh an average of 13 pounds (5.75 kg) and males weigh an average of 20 pounds (9.0 kg). The head and body of adult females are about 19 inches (49 cm) long, while adult males are about 20 inches (50 cm) long. Their tails are about as long, or slightly longer, than their head and body combined. They live to approximately the age of 30.
A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
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As their name suggests, common woolly monkeys have thick, woolly hair covering almost their entire bodies save their faces, hands, and feet, which are black. Their hair can be brown, tan, gray, olive, reddish, or black, and these color variations tend to vary somewhat with geography and subspecies. For example, gray and black individuals are more common at the base of the Andes in Colombia, while olive-colored individuals are most often found in Brazil. Geoffroy’s woolly monkeys tend to be a brownish gray while red woolly monkeys are usually, you guessed it, red. On some individuals, the hair is darker on their heads and limbs, while in others the hair is a uniform color throughout. Newborns are born tan and develop their adult coloring later in life.
Woolly monkeys’ close relation to spider monkeys is seen in their very long arms, legs, and prehensile tail, adaptations that make it possible for them to glide effortlessly through thick forests. They have an overall more stocky build compared to spider monkeys, however, including a generous potbelly! Males are larger than females and have longer canine teeth.
Common woolly monkeys are primarily frugivores, preferring fruit and supplementing their diet with leaves, seeds, and small invertebrates. They eat the fruits of more than 250 species of plants, and they favor figs and guava shrubs. They tend to prefer ripe fruit, and often eat seeds, leaves, and flowers instead when ripe fruit is not available. In July in Amazonian Brazil, insects make up a particularly large and important part of their diet.
Behavior and Lifestyle
Common woolly monkeys are arboreal, spending nearly all their lives in the trees, usually at a height of about 38 feet (12 m) above the forest floor. While they typically move at a slow, relaxed pace, if pressed they can reach a top speed of 35 mph (56 km/hr). They usually move about quadrupedally (on all fours), although they use their long arms, legs, and tails for brachiation. Also called arm swinging, brachiation is a form of arboreal locomotion in which primates swing from tree limb to tree limb using only their arms. On the rare occasions they find themselves on the ground, they can stand bipedally using their tail for support. They travel about 1 mile (2 km) per day, mostly staying in the forest canopy. Common woolly monkeys are diurnal and spend about equal parts of their day eating and foraging, moving, and resting. Their foraging style might be described as “leisurely,” taking their time as they move from tree to tree. During seasonal fruit shortages, they spend less time moving and socializing, and more time resting—likely an adaptation to the calorie shortage.
The Portuguese name for woolly monkeys is “barrigudo,” meaning “pot-bellied.”
The Bolivian population of Geoffroy’s woolly monkey has a much darker coat than Brazilian and Peruvian populations and is under consideration by wildlife biologists to classify it as a distinct subspecies.
Common woolly monkeys live in multi-male multi-female social groups containing anywhere from ten to 70 members. Groups follow a fission-fusion dynamic in which group composure tends to be fluid and not strictly defined. Larger groups are often composed of multiple family units that may feed or travel separately from each other during the day, coming together again to sleep. Some individuals, usually subadult females, may leave their own group temporarily, spending between a few hours to a few days with a different group before returning. Home ranges vary from 1.5 to 4 square miles (4–11 square km), and often overlap with other groups’ ranges. Individuals bond through grooming, which is most often directed at adult males. While aggression between group-mates can occur, usually between females, common woolly monkeys are generally a peaceful species and are not territorial. Adult males usually avoid each other, especially while feeding. Even during times of food scarcity, common woolly monkeys regularly interact and share space and feeding spots with neighboring groups. However, when mating opportunities are scarce, groups tend to keep to themselves more. Both males and females break off from groups to disperse and form or join new groups, although females are more likely to disperse than males.
Common woolly monkeys can communicate with each other in a large variety of ways. One important method is through facial expressions, which they can use to communicate subtle changes in mood or intention. Their vocalizations are loud, and include sounds described as “barks,” “screams,” “clucking,” and even “neighing.” The call of a male Geoffroy’s woolly monkey can be heard up to a quarter mile (400 m) away! Their vocalizations can be broken down into three types: contact calls, which provide information about the location and distance between individuals; alarm calls; and social interaction calls. Common woolly monkeys also use chest rubbing, a method of scent-marking. This is often used by dominant males when moving into new territory.
Males display antagonism towards each other by shaking branches, defecating, and barking. Affection is shown between group members by grooming, with adult males receiving the most grooming. Adult females are usually groomed by their daughters. Juveniles in a group bond with each other through play, which they often engage in around midday.
Common woolly monkeys reach sexual maturity at between four to eight years of age but females don’t typically give birth until about nine years of age. Females have a receptive period in their estrous cycle that lasts 3 to 4 days, occurring roughly once per month. Females indicate their readiness to mate through social cues. Both male and female woolly monkeys have more than one mate. A female usually demonstrates her receptivity to mating by shaking her head and baring and chattering her teeth at a male. Births are concentrated between May and September when ripe fruit is scarce. This allows female common woolly monkeys to accumulate energy reserves throughout their pregnancy from the abundant sources of food so that they are well-fed throughout gestation and have plenty of energy stored to use for lactation.
After a seven-and-a-half-month gestation, common woolly monkeys give birth to a single offspring, which is carried ventrally by the mother for the first month of life. After about six weeks, the baby more frequently climbs to their mother’s back. They begin to become independent after about two months of age, although they are nursed until they are about a year old. Curiously, one study of Geoffroy’s woolly monkeys found adult females nursing adult males! This was believed to be an alliance-fostering behavior. Female common woolly monkeys typically reach sexual maturity at about 6–8 years of age, while males mature at about five years of age. Females typically give birth every other year. Their generation length is about 15 years.
Woolly monkeys live alongside capuchins, howler monkeys, spider monkeys, and other primate species of the Amazon lowlands. The daily activities of the monkeys stir up insects, which serve as food for double-tooth kites, a small raptor, and these species are often found near each other. Woolly monkeys are also very important for seed dispersal, and a single fecal dropping can contain over 1,000 individual seeds.
The International Union for Conservation of Nature lists the common woolly monkey as Vulnerable (IUCN, 2020), appearing on the IUCN’s Red List of Threatened Species. This designation is based on a predicted population loss of 30% or more between 2018–2063, a time period comprising three generations. This is based on data showing forest loss trends throughout the species’ habitat, and the fact that common woolly monkeys are often hunted for meat. Some subspecies are even more at risk. Red woolly monkeys and Geoffroy’s woolly monkeys are both considered Endangered and are predicted to undergo a 50% population reduction over the next 45 years.
Like most threatened species, the major threat against common woolly monkeys is habitat loss. Over the last 50 years, an astounding 17% of the Amazon rainforest has been destroyed, most of it to clear space for cattle ranching. This is a staggering loss to global biodiversity, considering that the Amazon is the most biodiverse place on earth. This loss directly impacts millions of species, including woolly monkeys. Unfortunately, this loss is only expected to continue in the coming decades. Forest cover data from the Global Forest Watch shows a predicted 10–15% loss of forest habitat in parts of Brazil, Peru, Colombia, and Ecuador over the next 45 years.
Another threat against common woolly monkeys is hunting pressure. They are the single most frequently hunted primates in the Amazon region and one of the most intensely hunted primates in South America, mainly due to their large size resulting in their being relatively easy targets. The meat of woolly monkeys has been eaten by Amazonian communities for thousands of years. Traditionally, the meat was consumed mainly during festivals, although the meat is becoming increasingly popular in the illegal bushmeat trade throughout the region. As hunting technology improves, human population density increases, and Amazonian communities become more sedentary than nomadic, woolly monkey populations become increasingly threatened in areas near human settlements. As a result, some Amazonian people make expeditions into national parks and reserves to hunt and supply meat for festivals. In these protected areas, the unusually peaceful monkeys are unaccustomed to human encounters and are less cautious and easier to hunt, sometimes not reacting to human presence or even coming closer in an attempt to threaten hunters. Unfortunately, woolly monkeys are not uncommon in the pet trade. To collect infants, the mother must first be killed. It has been estimated that for every live common woolly monkey that reaches the pet trade market, at least 10 adult females have been killed.
Climate change also poses a potential threat to woolly monkeys. The changing climate may cause trees to flower and fruit at different times of year. Woolly monkeys, who are extremely dependent on fruit availability, move around to follow the fruiting of different trees at varying elevations. The desynchronization of fruiting cycles may cause significant stress to members of the species as they struggle to find adequate amounts of food. As climate change progresses and more research is conducted, we may find more ways that common woolly monkeys are impacted by this global phenomenon.
Common woolly monkeys are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival. They are protected by several protected habitats, such as Juami-Japurá Ecological Station in Brazil, Serrania de Chiribiquete National Natural Park in Colombia, and Cayambe-Coca Ecological Reserve in Ecuador.
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Written by K. Clare Quinlan, December 2022