GRAY WOOLLY MONKEY
Lagothrix lagothricha cana
Geographic Distribution and Habitat
The gray woolly monkey, also known as the Peruvian woolly monkey and Geoffroy’s woolly monkey (named for the French naturalist and explorer Étienne Geoffroy Saint-Hilaire [April 15, 1772–June 19,1844]), is a woolly monkey subspecies native to South America, inhabiting the Amazon rainforests of Brazil and Peru. An isolated population resides in Bolivia, and a related subspecies is found only in southeastern Peru.
Gray woolly monkeys are most prevalent in non-flooded areas of cloud forests, residing in trees 3,281 to 8,202 ft (1,000 to 2,500 m) above sea level. These tropical and subtropical damp forests (sometimes called fog forests) are characterized by persistent or seasonal low cloud cover. Beneath this canopy of clouds is an abundance of mosses, ferns, bromeliads (tropical plants with long, stiff leaves and showy flowers), and orchids. The Bolivian population has been found residing at much lower elevations, however: 2,300 feet (700) meters above sea level.
Woolly Monkey Taxonomy Controversy: Species vs Subspecies
Some scientists recognize the silvery woolly monkey (Lagothrix poeppigii), the gray woolly monkey (L. cana), and the Colombian woolly monkey (L. lugens) each as distinct species, sharing the genus Lagothrix.
Per a March 2020 report found in the International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species, recent genetic studies have provided support for there only being only two woolly monkey species: the brown (or common) woolly monkey (Lagothrix lagothricha) and the Peruvian yellow-tailed woolly monkey (Lagothrix flavicauda).
In this scenario, silvery, gray, and Colombian woolly monkeys are subspecies of the brown woolly monkey (Lagothrix lagothricha). This modifies their scientific names to Lagothrix lagothricha ssp. cana for the gray woolly, Lagothrix lagothricha ssp. lugens for the Colombian woolly, and Lagothrix lagothricha ssp. poeppigii for the silvery woolly. There is also a fourth potential subspecies of the brown woolly, Lagothrix lagothricha ssp. tschudii, Tschudi’s woolly monkey. (Very little is know about this fourth subspecies.)
The truth is that the woolly monkeys don’t care what we call them. They would certainly prefer that we leave them and their habitats alone and allow them to quietly live their lives. But we hope to allay any confusion you might encounter in your reading should you come upon conflicting scientific names, terminology, and taxonomy.
Size, Weight, and Lifespan
Head-to-body length in male gray woolly monkeys ranges from 18 inches to just under 26 inches (46 to 66 cm), with a weight of about 21 pounds (9.5 kg).
Head-to-body length in female gray woolly monkeys ranges from 18 inches to 23 inches (46 to 58 cm), with a weight of about 17 pounds (7.7 kg).
Tail length in these large New World primates adds another 26 inches (66 cm) to their bodies.
Gray woolly monkeys live to be about 26 years old.
Wide, strong shoulders and muscular limbs define the gray woolly monkey’s sturdy, hulk-like frame, which is covered with a thick gray coat as the primate’s name suggests. The monkey’s rounded head is a darker gray, and the ears are tiny. Deep brown eyes view the world. Face, hands, and feet are black, and inner arms are dark-colored. Gray woolly monkeys have well-developed thumbs and toes; their thumbs and fingers are short and thick with long, pointed nails. A generous potbelly suggests a beer gut! The gray woolly monkey’s prehensile tail functions as a useful appendage, gripping branches as the monkey travels from tree to tree. It is thick and muscular at the base, tapering to a thinner tip.
What Does It Mean?
An invertebrate animal (one with no spine) having an external skeleton, a segmented body, and jointed appendages. Includes insects, spiders, and crustaceans.
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Primarily frugivores, meaning that they eat mostly fruit, gray woolly monkeys select from at least 225 plant species. But their favorite fruits come from three flowering trees that produce mulberries, star apples, and pea-type legumes, respectively. Leaves and seeds are also on their menu, particularly when fruit is scarce. The occasional insect or spider might be a seasonal appetizer; however, these arthropods comprise less than one percent of the monkeys’ diet. Gray woolly monkeys spend more than 60 percent of their time, year round, foraging and eating.
Behavior an Lifestyle
Gray woolly monkeys’ foraging behavior might seem leisurely compared to other monkeys of the Amazon who move through the forest more swiftly, leaping from tree to tree. Gray woolly monkeys prefer to take their time as they deftly advance through the rainforest’s upper canopy. Rarely do they leap between trees; however, they make good use of their prehensile tail which allows them to bridge gaps between trees and lets them hang from a tree branch while they select a piece of fruit. Mid-day rests are taken; at night, gray woolly monkeys sleep high in the dense treetops.
Arboreal creatures, meaning that they spend virtually their entire lives in trees, gray woolly monkeys are excellent climbers. On the rare occasion when they set foot on the ground, they walk upright, on two legs, using their arms and tail for balance.
Daily Life and Group Dynamics
Gray woolly monkeys live in mixed-gender groups, known as troops, of 11 to 25 members; individuals vary in age. The oldest males hold dominant ranking. However, dominant males practice extreme tolerance toward other males in the group, even permitting them to mate with the group’s females. Among primates, gray woolly monkeys engage in what is considered a lengthy mating ritual: all of four minutes!
Daylight hours are devoted to foraging high in the tree tops. A troop travels together throughout its home range, sharing food with one another thereby strengthening their social bonds. In a gesture of supreme etiquette, a troop will graciously share its prime feeding spots with other gray woolly monkey troops. Little aggression arises between troops, who often forage side by side.
Brazilians refer to the gray woolly monkey as macaco barrigudo, or “big-bellied monkey,” because of the primate’s protruding abdomen.
The Bolivian population of gray 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.
Vocal communication among gray woolly monkeys includes “clucking” calls and loud “neighing” calls, made by the males of a group. A male gray woolly monkey’s neigh can be heard up to a quarter mile (400 meters) away. These vocalizations are used during foraging activity.
Woolly monkeys have been observed using olfactory (scent), visual, and tactile cues to communicate with one another.
Reproduction and Family
Little information is available on biology and reproduction specific to gray woolly monkeys. However, general conclusions can be made from what is known about common woolly monkeys.
Male woolly monkeys reach sexual maturity at just over 5 years of age. Females reach sexual maturity later, between 6 and 7 years of age. The gestation period (length of pregnancy) is about 7.5 months and a single infant is born, usually every two years. For the first month of their lives, babies are carried by their mothers on her abdomen. At six weeks of age, babies climb onto their mother’s back. Mothers nurse their babies up to 12 months, at which time the young are considered weaned.
However, a 2013 study of gray woolly monkeys living in a wildlife conservation area revealed unusual occurrences of weaning: adult females were observed breastfeeding adult males. The wildlife biologists conducting this study offered three hypotheses for this activity: it represented an example of extended maternal care; it was a curious and opportunistic act of “foraging”; or the activity was intended to foster alliances. Alliance-fostering was decided as the most plausible explanation. With a motive to maintain or advance their hierarchal status within the troop, nursing females are thought to permit this unusual liberty to adult males.
Woolly monkeys live sympatrically with capuchins, howler monkeys, spider monkeys, and other primate species of the Amazon lowlands. Their predators include birds of prey and large carnivores, such as jaguars. Their mostly frugivorous diet makes them important seed dispersers.
Conservation Status and Threats
The gray woolly monkey is classified as Endangered by the International Union for Conservation of Nature (IUCN,2020) appearing on the IUCN Red List of Threatened Species.
Scientists anticipate that habitat loss alone will have led to 50 percent loss in the species’ population in the next 45 years. The clear-cutting of forests for agricultural use and for illegal mining operations has caused the disappearance of much of the gray woolly monkey’s habitat. But it’s the illegal pet trade that may sound the death knell to the species—unless serious conservation efforts are implemented and enforced.
In addition, and perhaps more significantly, they are heavily hunted for their meat, as well as for the pet trade. According to some studies, population densities of heavily-hunted Lagothrix species can be expected to decline by more than half over several generations.
Because of their large size, gray woolly monkeys have few natural predators, other than humans who hunt them for their meat. Eagles are a potential threat to young and smaller gray woolly monkeys, however.
Unfortunately for gray woolly monkeys, they have become popular pets. Mother gray woolly monkeys are shot and killed, and their babies are stolen.
One anecdotal story reports that in the span of two years, hunters in the Amazon killed more than 200 woolly monkeys, leading to localized extinction in the area where the monkeys had once lived.
The gray woolly monkey is 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. Monitoring the species and adherence to this agreement is difficult to conduct and enforce, however, and the agreement is often ignored by those engaged in illegal activities.
National parks play a key role in preserving the species, offering protection to gray woolly populations who live within the parks’ borders. Bolivia’s entire known range of gray woolly monkeys lives in two of the country’s protected areas. Brazil has established several national parks where gray woolly monkeys are protected.
Wildlife Conservation Society-Brazil (WCS-Brazil) is a Brazilian non-profit organization, founded in 2003, working to “identify critical conservation problems and develop science-based and community-driven solutions that benefit natural landscapes, wildlife, and human populations.” The gray woolly monkey is within WCS-Brazil’s purview.
Affiliated with the Wildlife Conservation Society, the oldest conservation non-governmental organization (NGO) in North America whose headquarters is located at New York’s Bronx Zoo, WCS-Brazil focuses on local outreach. Convinced that woolly monkeys are icons for conservation because of the vital roles they play in their ecosystem as seed dispersers, WCS-Brazil disseminates environmental education to local people, encouraging them to engage in the preservation of the woolly monkey species and the species’ habitats.
WCS-Brazil’s localized conservation efforts are funded through The Mohamed bin Zayed Species Conservation Fund, a significant philanthropic endowment established to “provide targeted grants to individual species conservation initiatives, recognize leaders in the field of species conservation, and elevate the importance of species in the broader conservation debate.”
Written by Kathleen Downey, October 2016. Taxonomy and conservation status revised July 2020.