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Suborder: Haplorrhini
Infraorder: Simiiformes
Family: Atelidae
Subfamily: Atelinae
Genus: Brachyteles
Species: B. arachnoides, B. hypoxanthus

Other names: woolly spider monkey; ulden edderkoppeabe (Danish); spinaap (Dutch); muriki (Finnish); atèle arachnoïde, eroïde, or singe-araignée laineux (French); spinnenaffe (German); murichi (Italian); mono arena, mono carvoeiro, mono grande, muriki (Spanish); kortullig spindelapamirikinordlig ullspindelapa; mirikinordlig ullspindelapa, ullhårig spindelapa, ullig spindelapa, or ullspindelapa (Swedish); B. arachnoides: muriqui, woolly spider monkey, southern muriqui, or southern wooly spider monkey; B. hypoxanthus: muriqui, northern muriqui, or northern woolly spider monkey

Conservation status: please search the IUCN Red List.

Life span: Unknown
Total population: 700 (wild)
Regions: Brazil
Gestation: 7.2 months (216 days)
Height: 490 mm (M), 486 mm (F)
Weight: 9.6 kg (M), 8.4 kg (F)

The name muriqui comes from the Tupi Indians of Brazil, but they have also previously been called woolly spider monkeys. The use of the name woolly spider monkey has fallen out of favor, as the term is misleading, implying that the animal is a hybrid of woolly monkeys (Genus Lagothrix) and spider monkeys (Genus Ateles), when in fact muriquis are unique (da Fonseca 1985a; Strier 1992a). Once considered to be two subspecies, B. a. arachnoides and B. a. hypoxanthus were elevated to species level in 1995 based on geographic distribution as well as morphological differences. The two species are completely geographically isolated from each other and interbreeding is not possible in the wild (Strier 1986; Rylands et al. 1995; Groves 2001).


Muriqui hanging from branch

The common name for members of the genus Brachyteles, woolly spider monkey, comes from the thick, fleecy appearance of their fur. They range in color from gray to yellow-brown and fur covers their bodies except for their faces, which are bare. The two species are distinguished from each other as the northern species, B. hypoxanthus, has a black face while the southern species, B. arachnoides, has a black face mottled with pink. Northern muriqui infants are born with black faces which become mottled as they age (Lemos de Sá et al. 1993; Strier & da Fonseca 1996/1997; Groves 2001). In addition to the difference in facial skin pigmentation, northern and southern muriquis vary in dental morphology. The canine teeth of male southern muriquis are much longer than females of the same species and longer than those of northern males. There is no sexual dimorphism seen in the canine teeth of northern males and females (Lemos de Sá et al. 1993; but see Leigh & Jungers 1994).

Another difference between the two species is the presence of an opposable thumb. Among southern muriquis, the external thumb is entirely missing while in northern muriquis, there is a vestigial thumb; it is rudimentary and abbreviated compared to other species of primates (Rosenberger & Strier 1989; Lemos de Sá & Glander 1993; Groves 2001). Even though they do not have a true thumb, this does not mean that muriquis are less evolved than other primates. In fact, the muriqui’s ancestor had a thumb, but over time the hand became more specialized and the thumb shrunk. One hypothesis is that the thumb was no longer an essential part of locomotion as the prehensile tail evolved (Hartwig 2005). All muriquis have a prehensile tail, a specialized tail used in suspensory locomotion that is seen only in a few species of New World monkeys. Both the small or absent thumb and the prehensile tail seen in muriquis are related to the patterns of movement that characterize the genus: suspensory climbing and rapid brachiation (Rosenberger & Strier 1989). On the underside of the tip of the tail is a patch of bare skin or friction pad, which aids in grip. Having a ‘third hand’ allows muriquis to grasp branches for stability during travel or while feeding, to increase fluidity of motion during travel, and to hang solely by their tails to reach foods with both free hands (Rosenberger & Strier 1989). Muriquis are the largest of the New World monkeys, appearing almost five feet tall when hanging by their long arms from tree branches. In both species, males and females are about the same size, with adult males weighing 9.6 kg (21.2 lb) and adult females weighing 8.4 kg (18.5 lb) on average. Height from the head to the base of the tail is 486 mm (1.59 ft) in females and 490 mm (1.61 ft) in males (Lemos de Sá & Glander 1993). These are currently the best estimates for weight and body size available for both species, but they are based on a small sample size (five males and seven females, various ages). As more animals are captured and measured, the average heights and weights may change and reveal differences in size between the sexes (Lemos de Sá & Glander 1993; Peres 1994).


Brachyteles arachnoides | Brachyteles hypoxanthus

In the wild, muriquis are restricted to small, isolated patches of Atlantic coastal forest in Brazil (Lemos de Sá et al. 1993; Strier 1992a). They are distinctly separated into northern and southern regions with the northern region including populations in the states of Minas Gerais, Espírito Santo, and Bahia and the southern population existing in the states of southern Minas Gerais, southern Rio de Janeiro, and São Paulo (Strier 1992a; Pope 1998). The populations are separated not only by human development and lack of contiguous forest but also by riverine barriers such as the Rio Grande, the Rio Paraiba do Sul, or the Serra da Mantiqueira (Lemos de Sá et al. 1993).

Long-term research on northern muriquis has been the work of Karen Strier and her Brazilian colleagues since 1982 at the RPPN Feliciano Miguel Abdala (previously known as the Estação Biológica de Caratinga) on Fazenda Montes Claros, a privately owned ranch (Strier 1986; Strier & Boubli 2006). This privately owned property has been protected by the landowner and has been the source of many major discoveries about muriqui behavior and biology. Northern muriquis have also been studied at Fazenda Esmeralda in Minas Gerais, Reserva Biologica Augusto Ruschi in Espírito Santo, and additional field studies are underway at other sites in these states (Dias et al. 2005; Mendes et al. 2005). Important study sites of southern muriquis include Fazenda Barreira Rico and Parque Estadual de Carlos Botelho in São Paulo State (Milton 1984; Talebi et al. 2005). The muriqui population at Carlos Botelho lives in one of the largest undisturbed tracts of Atlantic coastal rainforest where muriquis can be found (de Moraes et al. 1998; Talebi et al. 2005).

There are fewer than 2000 muriquis remaining in the wild (Strier 2000; Mittermeier et al. 2005). The captive population of muriquis is tiny and according to the International Species Information System, a database for animals kept in captivity around the world; there are only two captive populations and they are found in Brazil ( Captive breeding efforts have been met with limited success because muriquis have not been removed from the wild to start a captive population. The captive stock in breeding facilities such as the Centro de Primatologica do Rio de Janeiro is entirely composed of sick or orphaned animals brought to them which must be nursed back to health. Because they do not draw from wild populations, they cannot choose which species or sex to bring into captivity and must rely on fate to develop a breeding population (Strier & da Fonseca 1996/1997). A captive population of southern muriquis is also housed at the zoo in Curitiba, Brazil (Strier pers. comm.).


All wild muriquis are found in highly fragmented patches of Atlantic coastal forest, a once widespread ecosystem spanning several states on the southeastern coast of Brazil which has been reduced in size to less than 5% of its original area (Strier & da Fonseca 1996/1997). Originally, the Brazilian Atlantic coastal forest was an area of exceptional species diversity and high levels of endemism but over time, as forest has been cleared for crops, pastures, timber, and human settlement, the forests have been severely altered (da Fonseca 1985b). Despite this rampant habitat destruction, muriquis survive in several isolated patches of both primary and secondary forests between 600 and 1800 m (1969 and 5906 ft) above sea level and exhibit flexibility in their habitat requirements (da Fonseca 1985a; Strier 1987a; Lemos de Sá & Strier 1992).

Muriqui clinging on branch

Southern muriquis studied at Fazenda Barreiro Rico in São Paulo State live in tall, primary semideciduous forest with some patches of secondary growth. While they prefer the older, taller areas of forest, they are capable of using disturbed patches and find vines to feed on in these lower areas (Milton 1984). The average annual rainfall at Barreiro Rico is 1263 mm (4.14 ft), with the heaviest rainfall concentrated in a six-month period from October to March. Less rain falls from April to September. The wettest months of the year are December and January while the driest months of the year are July and August. The annual temperature ranges between 8° and 35° C ( 46.4° and 95° F), and can get as cold as 0° C ( 32° F) (Milton 1984). In the large area of undisturbed Atlantic coastal forest at Parque Estadual de Carlos Botelho, primary, late successional forest can be found and annual rainfall averages 1685 mm (5.53 ft) (de Moraes et al. 1998).

In the north, muriquis live in variable conditions and exploit both primary forest, where available, as well as highly disturbed areas of secondary vegetation (Lemos de Sá & Strier 1992). At Fazenda Montes Claros in Minas Gerais, average annual rainfall is between 1000 and 1200 mm, with the rainy season lasting from November through April and the dry season extending from May through September (Strier et al. 2001). Temperatures vary from 12° to 29° C (53.6° to 84.2° F) throughout the year (Strier 1986). The forest composition at this study site has been dictated by human use patterns and ranges from undisturbed primary forest to regenerating secondary forest and scrub forest (da Fonseca 1985a). The dominant tree species are not the same as those found in São Paulo, and forest composition differs greatly between the two sites, further amplifying the ability of muriquis to cope with a diversity of habitat availability (Strier 1986).


Muriquis have physical adaptations allowing them to exploit both large quantities of leaves as well as move efficiently between fruit trees that are dispersed over large areas. Folivorous primates are generally large-bodied, have specialized digestive tracts to maximize nutritional gains from a comparatively poor food resource- leaves- and have dental adaptations for chewing and breaking down huge amounts of fibrous leaves (Zingeser 1973). Frugivores, which consume a high-quality, nutrient rich resource have adaptations most effectively forage for these resources which are less abundant and more widely dispersed than leaves (Gaulin 1979). Muriquis exhibit dental and gastric adaptations for consuming leaves as well as a prehensile tail and hook-like hands for traveling quickly and efficiently between fruit trees and indeed their diet reflects this folivorous-frugivorous diet combination (Strier 1987a).

Multiple Muriqui in tree

The majority of their diet is composed of leaves and fruit, but they also eat flowers, bark, and buds (Strier 1991a). There are differences in the amount of leaves and fruits consumed when comparing northern and southern muriquis as well as between study sites. At Fazenda Montes Claros, diet varies according to resource availability throughout the year, but annually they spend 51% of their time feeding on leaves, 32% to fruits, 11% to flowers, and 6% to other foods such as bark, bamboo, buds, and ferns (Strier 1991a). They spend a higher percentage of their time feeding on fruit when it is available and more time feeding on flowers when they are abundant. Leaves are an important source of energy throughout the year, and they eat leaves consistently throughout the year to add bulk to their diet (Strier 1991a). At Fazenda Barreiro Rico, muriquis are more folivorous compared to Montes Claros, spending 67% of their time feeding on leaves and only 21% on fruits and 12% on flowers (Milton 1984). One possible reason the diets of the two species are divergent is because of the difference in forest structure at the study sites. Montes Claros has larger trees more likely to supply fruit whereas the forest at Barreiro Rico is mostly regenerating and has far fewer large, fruiting trees and more vines (Strier 1986). In pristine forests within their range, southern muriquis exhibit higher levels of frugivory than northern muriquis, indicating the reliance on leaves in other areas is directly related to lower levels of fruit availability due to habitat degradation and fragmentation (de Carvalho et al. 2004; Talebi et al. 2005). At Parque Estadual Carlos Botelho in southern São Paulo state, muriquis spend 71% of their time feeding on fruit compared to 24% on leaves. The remaining feeding time is spent on other food items. When ripe fruits are scarce, southern muriquis at Carlos Botelho consume unripe fruits in small amounts and supplement their diet to a greater degree with leaves, compared to other times of the year (Talebi et al. 2005).

The daily activity patterns of muriquis includes resting, feeding, traveling, and socializing. They have been described as inactive compared to other species of primates, and spend an average of 49% of their day resting compared to 29% traveling, 19% feeding, and 2% socializing and engaging in other activities (Milton 1984; Strier 1987b). The muriquis of Barreiro Rico are late risers, getting up between 8:00 and 10:00 a.m. and feed while traveling until the afternoon, when they have a period of rest lasting between two and three hours. They feed heavily in the late afternoon hours before retiring to their sleeping site for the evening around dusk (Milton 1984). At Montes Claros, travel patterns vary by season. In the summer, muriquis wake up and begin to travel as the sun rises, spending the mornings traveling and feeding and taking an afternoon rest beginning at midday, when temperatures are at their peak. On cold winter mornings, they do not begin to stir until mid-morning and are more leisurely in their pace, spending time to warm themselves in the sun and retiring earlier than in the summer months (Strier 1987b; 1992a).

Muriqui leaping from one tree to another

At Montes Claros, the study group of northern muriquis lives in a home range of 1.68 km² (.649 mi²) which overlaps with another group in this protected forest. Day range length estimates range between 141 and 3403 m (.088 and 2.11 mi) but average 1283 m (.797 mi) traveled each day (Strier 1987a). During the wet season, from November to April, muriquis travel substantially longer distances compared to the dry months, which are between May and October (Strier 1986). Compared to southern muriquis at Fazenda Barreiro Rico, whose home range of .70 km² (.27 mi²) and average daily path length 630 m (.391 mi), northern muriquis at Montes Claros travel farther over larger home ranges (Milton 1984). This may be in response to the difference in quality of the habitat at the two sites. At Montes Claros, large food patches are common and the muriquis travel further to accommodate the larger group size in order to decrease feeding competition between group members. At Barreiro Rico, where there are fewer muriquis living in smaller groups and highly dispersed patches of quality food resources, the monkeys travel less distance. The feeding competition is not as high among the southern muriquis, and the added energy of traveling great distances between trees is not worth the return (Strier 1986; 1987a; Lemos de Sá & Strier 1992). At Carlos Botelho, the home range size of a group of muriquis is much larger than at Montes Claros and Barreiro Rico, averaging eight square kilometers (3.09 mi²) and owing to the larger tracts of forest found in the park than anywhere else that muriquis are studied (de Moraes et al. 1998). Despite having more and larger food patches, muriquis at Carlos Botelho live in smaller groups than at Montes Claros. One reason for this grouping pattern may be that in order to have the most frugivorous diet possible, smaller parties are necessary to exploit the resources efficiently. The other consideration is that muriquis at Montes Claros live under unnaturally strained conditions in terms of space available and population density but have adapted to maximize their diet (de Moraes et al. 1998).

Natural predators of muriquis include felids, such as jaguars, as well as raptors, but because top predators require large home ranges, the isolated patches of forest in which muriquis live do not support these animals in high enough numbers to create a critical threat for muriquis at Barreiro Rico and Montes Claros. Furthermore, where there are few natural areas to hunt surrounded by areas of human agriculture, predators sometimes survive on livestock, lowering the human tolerance for these animals and increasing persecution and decreasing overall predator populations (Lemos de Sá & Strier 1992; González-Solís et al. 2001; Chiarello 2003). Other smaller potential predators include mustelids, which have been circumstantially linked to the disappearance of infant muriquis at Montes Claros (Printes et al. 1996). The predator population at Carlos Botelho is more intact than at the other study sites and can support large animals such as jaguars, which could contribute to muriqui mortality at this site (de Moraes et al. 1998).

Content last modified: August 30, 2006

Written by Kristina Cawthon Lang. Reviewed by Karen Strier.

Cite this page as:
Cawthon Lang KA. 2006 August 30. Primate Factsheets: Muriqui (Brachyteles) Taxonomy, Morphology, & Ecology . <>. Accessed 2020 July 16.


In addition to affecting their diet, the geographic dispersal of resources influences the grouping patterns and social structure of muriquis. At the two study sites where muriquis have been studied systematically, Montes Claros and Barreiro Rico, the structure of social groups varies (Strier 1987b). At Montes Claros, where large fruiting trees are more abundant and closely spaced, muriquis live in social groups of 20 to more than 80 individuals which travel and feed together throughout the day. In contrast to the large social groups present at Montes Claros, muriquis live in small groups at Barreiro Rico, where fruit trees are scarcer and widely dispersed. The only permanent associations at this site are between adult females and their offspring, and social groups consist of three to five adult females and their dependent offspring. These units travel alone and are joined, on occasion, by subadult and adult males (Milton 1984). The female groups remain in discrete home ranges. The males travel alone or in groups of up to eight individuals, joining different groups of females for short periods to mate and then moving on to find other estrous females. Associations between adult males and females at Barreiro Rico last between a few minutes to over a week (Milton 1984).

Multiple Muriqui in tree

The abundance of feeding sites at Montes Claros might allow larger groups to form and stay together without costly competition for resources at feeding sites (Strier 1989; Strier et al. 1993). In fact, after several years of growth resulting in an almost doubling of group size, the study group at Montes Claros shifted its behavior from maintaining a large, cohesive group, to two smaller groups that come together often, but frequently travel separately. Unlike the small groups at Barreiro Rico, the groups come together regardless of female receptivity (Strier et al. 1993). This change in behavior was accompanied by a widening of the home range size, indicating that there is a positive relationship between resource availability and muriqui social group size and home range size (Strier 1989; Dias & Strier 2003). As of 2006, there were four muriqui groups in this forest and a total population of 226 individuals (Strier et al. 2006).

Information about the social structure of muriquis comes chiefly from the long-term research at Montes Claros. Muriquis exhibit male philopatry, staying in the groups where they were born while females leave their natal groups between five and seven years of age to join another group, where they will stay and mate for life (Strier 1991b; 1996). Young females often leave their natal group shortly after an agonistic encounter with a neighboring group (Strier 1993). They are not forced out by older females, as is seen in some other primates such as the callitrichines, but seem to part from their group amicably (Strier & Ziegler 2000). Aggression in muriquis is exceptionally rare, but when a female attempts to join a social group, she is chased and displaced by the adult females in the group (Strier 1991b; 1992b). Adult resident females frequently displace young immigrants at quality feeding sites and young females remain on the periphery of the social group (Printes & Strier 1999). Young female immigrant muriquis gain acceptance by playing and interacting with juvenile or subadult females of the group, and eventually the adult females will tolerate their presence (Strier 1991b; 1992b; 1996).

Males within the same group are likely to be related, because of the dispersal patterns exhibited by muriquis, and do not behave agonistically to one another, even in the presence of reproductive females (Strier et al. 2002). There is little evidence of dominance relationships either between females, between males, or between females and males (Strier 1992b). Embracing or affiliative hugging is one way in which social relationships are strengthened among male muriquis while social grooming is rare (Strier 1994; Strier et al. 2002). Though muriquis of the same group have egalitarian relationships, interactions between males of neighboring groups are hostile. Vocal displays, threat displays, and chasing characterize interactions between males of two groups which come into contact with one another. This agonistic behavior may be to prevent intruder males from coming into contact with females of a social group (Strier 1994). Related males of a social group work together to keep strange males from entering the group; when males cannot prevent outsiders from coming into contact with females, the new males often copulate with group females (Strier 1994).


Muriqui hanging from branch

Muriquis are promiscuous and exhibit a polygamous mating system in which both males and females mate with multiple partners (Milton 1985; Strier 1986). At Montes Claros, females mate with an average of eight different males during the mating season and males mate with an average of 14 different females (Strier 1997). Mating is concentrated during the months from September through March and births occur primarily during the peak dry months, June through August (Strier 1991b; 1996; 1997). Reproduction is correlated with rainfall and thus availability of new leaves, an important food source for muriquis after the dry season shortages (Strier 1996). In the dry season, when day ranges are shorter, muriqui mothers with highly dependant infants may benefit because they do not have to expend extra energy traveling long distances while carrying an infant. As fruiting begins, the infant has grown and is less awkward to carry because it is larger and has more strength and the female can travel the longer distances seen during the wet season (Strier 1986; 1996).

Females reach puberty after transferring from their natal group and experience a delay in the normalization of their ovarian cycle which lasts about 14 months after transferring, or at least one breeding season (Strier & Ziegler 2000). Females do not cycle throughout the year but rather only during the mating season (Strier & Ziegler 1994). The ovarian cycle lasts an average of 21 days, but can range between 16 and 38 days, and there are no external signs of ovulation (Strier & Ziegler 1997). Females copulate at 20 day intervals during the mating season and may mate over several reproductive cycles (Strier & 1997). The age at first reproduction for females has only been documented in only a few females whose birth dates are known and occurs between 7.5 and nine years of age (Strier 1996; Martins & Strier 2004). Gestation lasts about seven months (averaging 216 days) and there is a long interbirth interval, averaging 36 months (Strier 1996; Strier & Ziegler 1997).

Males begin to reproduce around five or six years of age (Strier 1996). Aggression or physical competition for access to mates has not been documented among muriquis, and one hypothesis is that physical adaptations in males reduce the need for overt competition and instead, sperm competition is practiced (Strier 1992a; 1997). Male muriquis have large testicles compared to their body size and larger testes result in higher levels of sperm production (Strier 1992a). Among animals in which males and females mate with multiple partners, there is potentially an advantage to a male that can produce the largest amount of sperm; he has a higher chance of successfully fertilizing a female compared to other males (Dixson & Anderson 2002).


Muriqui mother and infant in tree

Infants are born with light fur and dark faces and they begin to lose their natal coat and skin pigmentation between three and four years of age. They do not reach adult size until they are between five and seven years of age (Strier 1993). Female muriquis are the sole caregivers of their offspring, carrying and nursing their infants as they slowly gain independence and are eventually weaned (Strier 1993). Adult males have been characterized as indifferent to infants within their group and rarely come into contact with them. Interactions are friendly but brief, and are always initiated by the infants (da Oliveira Guimarães & Strier 2001).

For the first year of life, muriqui infants are almost fully dependent on their mother for transportation and food. During the first six months, the infant clings to the fur on its mother’s belly and sides and is awkward to carry for the mother. As the infant matures, it begins to ride jockey-style on its mother’s back, wrapping its prehensile tail around its mother’s tail for added support (Strier 1992a; 1993). The two remain in almost constant contact during the early months, and gradually decrease contact time. The mother may leave her infant on a thin branch while she feeds next to it but will always gather it up before moving to the next feeding or resting site. Six to 12-month old infants are never more than a few feet from their mothers, and spend time tentatively exploring while their mother is feeding or resting (Strier 1992a).

After the first year, young muriquis gain more independence from their mothers and are able to travel short distances without the help of their mother. Groups of infants are often parked together and socialize through play while the mothers feed (Strier 1992a). In some instances, young muriquis require the assistance of their mothers to negotiate large gaps in the canopy. In these cases, the mother will form a bridge, using her long, prehensile tail and her front legs, stretching the length of the gap and allowing her young to cross over her (Strier 1992a).

Weaning occurs between 18 and 24 months, though experimentation with solid foods occurs months before. The weaning process is often a traumatic time for the juvenile muriqui. Mothers refuse nursing attempts of their juvenile offspring by hitting or nipping at them when they try to suckle, and young muriquis may throw tantrums, screeching and whining until they are allowed to nurse or grow tired (Strier 1991b; 1992a). Young muriquis begin to forage completely on their own at around two years of age (Strier 1992a). In the breeding season after her infant is weaned, the mother will begin to copulate and will likely conceive. The interbirth interval is about 36 months, but the average interval between parturition and resumption of copulation is 23.5 months (Strier 1996). A young muriqui is about three years old when its sibling is born, and by this time is completely independent from its mother (Strier 1992a).


Muriquis communicate through vocalizations, postural behavior, and chemical communication. One common vocal call is the “neigh,” which is a loud, horse-like call given frequently in the early morning, during travel, and at the end of the day before entering the sleeping tree. One function may be to inform other animals of an individual’s location and maintaining group unity throughout the day when muriquis cannot see one another (Torres de Assumpção 1984; Strier 1986; Nishimura et al. 1988). It may also serve as a spacing function for other muriqui groups in the area, communicating the location of the one group to another (Strier 1986). When two muriqui groups come into contact, the most common vocalization is the “bark.” Much like the hoarse-sounding bark of a dog, adult male and female muriquis bark at two- to three-second intervals before, during, and after an intergroup encounter (Milton 1984; Strier 1986; Nishimura et al. 1988). Mild anxiety among muriquis is expressed by “hoots,” and can be heard after long barking bouts. Females traveling with young can be heard giving “cluck” calls, a soft smacking call that may be a reassuring sound to infants or juveniles left in one part of the tree while the mother forages elsewhere in the tree (Strier 1986). The common feeding call given by both adult males and females is the “chirp.” Infants and juveniles make calls when they are upset, during weaning and when they are left behind by the group. These include “screams” and “whines,” both of which usually result in a response from their mothers (Strier 1986).


Some vocalizations are accompanied by physical displays. Adult male muriquis often embrace both as a friendly gesture and during times of extreme excitement. “Clucks” are given during friendly embraces, but sometimes embracing escalates when males are agitated, such as after an intergroup encounter, and several males will frantically embrace each other and emit “warbles,” throaty gurgling calls (Strier 1986). Another greeting gesture seen between adult males and adult females, but not between members of the opposite sex, is a ritualized embrace in which the two animals emit “staccato chutter-whinnies” and hug forcefully, both animals pulling their lips back over their teeth into a grimace (Milton 1984). Other display behaviors include slapping leaves and branches with the hands, forcefully pulling branches back and letting them go, lunging, and defecating (Milton 1984).

Adult male and female muriquis use chemical communication to convey sexual receptivity and interest to members of the opposite sex. Both males and females communicate via urine washing; they urinate directly onto the hands, feet, or tail, and rest the coated appendage on branches, leaving a trail as they walk or hang by their tails for other animals to encounter (Milton 1985).

Content last modified: August 30, 2006

Written by Kristina Cawthon Lang. Reviewed by Karen Strier.

Cite this page as:
Cawthon Lang KA. 2006 August 30. Primate Factsheets: Muriqui (Brachyteles) Behavior . <>. Accessed 2020 July 16.


For individual primate species conservation status, please search the IUCN Red List.
Also search the current scientific literature for primate conservation status (overall as well as for individual species), and visit CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora).

Conservation information last updated in 2006 follows, for comparison:

Muriqui in tree

The most serious threats to muriqui conservation include habitat loss and fragmentation as well as illegal hunting. While Brazilian law protects remaining stands of Brazilian Atlantic forest and many muriqui populations exist on private lands, land clearing and hunting continue to threaten their survival (Strier 1992). It is estimated that there are fewer than 2000 muriquis left in the wild (Strier 2000; Mittermeier et al. 2005).


Threat: Human Induced Habitat Loss and Degradation

The loss of the Brazilian Atlantic forest dates back to the 1500s, when Portuguese explorers first entered Brazil and began to establish ports and trading posts. The forest was first cleared for sugar cane, an important export crop, but other natural resources such as gold and diamonds were soon discovered and extracted (da Fonseca 1985). As the economy boomed, human populations grew and more land was cleared for agriculture, an industry that has continued to expand in this region of Brazil since the 17th century. The human population of Brazil is concentrated in this area and as a result of centuries of forest clearing and land exploitation, only a fraction of the Brazilian Atlantic forest remains (da Fonseca 1985; Morellato & Haddad 2000). Endemic fauna and flora of this region have either been pushed to extinction or, like muriquis, are in serious threat of disappearing because the unique forest in which they evolved has been all but eliminated (Morellato & Haddad 2000). Ongoing human activities with a major impact on muriqui habitat loss and destruction include sprawling coffee plantation and cattle grazing, both of which occur on land cleared by fires, small-scale timber extraction, hydroelectric dams, and road development. Another human-induced cause of habitat degredation is palm heart harvesting, an important export resource (Rylands et al. 1998).

Agriculture continues to be an important part of the economy in this region of Brazil and the land has been parceled out for centuries. While some plantation owners have stands of primary and secondary growth which can support muriqui groups, there is uncertainty in the future ability of landowners to protect these stands for muriquis as economic incentives to either clear the land for timber or additional pasture and crop land still exist. Furthermore, because so much of the land in the region is privately owned, acquiring land for parks and reserves is nearly impossible as it would mean buying multiple adjacent properties to establish one suitable plot for forest regeneration (da Fonseca 1985).

Land fragmentation has been particularly devastating to the northern muriqui, whose populations are isolated from each other, compared to the southern muriqui, which survives in one of the largest tracts of Brazilian Atlantic forest remaining, Serra do Mar in Rio de Janeiro and São Paulo (Strier 2000; Mittermeier et al. 2005). In addition to losing places to establish home ranges, habitat destruction can cause ecological stress and influence the way in which muriquis forage and the overall composition of their diet. This can lead to lower rates of reproduction and slower population growth (Strier 1992a).

Potential Solutions

The single most important factor in conserving muriquis is protecting forest from further destruction and fragmentation (Brooks & Rylands 2003). One solution is the private faunal refuge system administered by the Brazilian Institute of Forest Development (IBDF) in which private land owners have legal backing to prohibit hunting on their lands. Small, adjacent private reserves can be useful in preserving connecting tracts of regenerating forest and provide refuge for endangered species such as muriquis (da Fonseca 1985; Strier 1992). Despite historical habitat destruction, in areas where forests are allowed to regenerate through protection such as at Montes Claros, muriqui populations show marked growth. Given larger areas of suitable habitat, muriquis have been able to expand their home ranges and increase their overall population size, indicating that habitat protection is a sensible and worthwhile endeavor (Strier 1992; 2000).

One incentive for private landowners to curb habitat destruction and create economic opportunity is through ecotourism. By protecting forests and creating ecotourism destinations on their lands, private landowners can personally gain from having muriquis on their land (Strier 1992a). Montes Claros is a popular tourist site, with income from visitors contributing to continuing research (Strier 1992a). At other sites, income could be split between researchers and land owners, or could solely benefit landowners.

Threat: Harvesting (hunting/gathering)

Muriquis are the largest of the New World primates and are prized trophies for hunters. Not only are they sought after because of their large body size, they may also experience heightened risk because they are easily spotted by hunters (Pinto et al. 1993). Where they are found in state parks and reserves, there are too few guards to effectively protect against poaching. Private landowners are more successful in preventing trespassers from hunting muriquis living on their land, but illegal hunting still occurs (Strier 1992a). Hunting is particularly devastating for small populations in isolated forest fragments where poachers can essentially drive a group to local extinction either through directly killing adults or disrupting the population structure so significantly that the group cannot rebound (Chiarello 2003).

Potential Solutions

Hunting of muriquis is illegal, and prosecution of poachers is one way to deter hunting, but apprehension of hunters is necessary if they are to be prosecuted. Eliminating illegal harvesting of muriquis is a near-impossible endeavor as parks and private lands are scarcely patrolled by guards and forests are often difficult to effectively patrol. One method of decreasing poaching is to accentuate the cultural or economic value to the muriquis through education or ecotourism. For example, while the muriqui has become a flagship species of the region, appearing on postage stamps, telephone directories, t-shirts, and posters, continuing education and information dissemination is critical to teach people about the unique resource found in nearby forests (Strier 1992a). Ecotourism, which often gives an economic value to protecting wildlife, is another option for involving local people in conservation measures. Providing alternate sources of income as field guides or other service related jobs could change attitudes about hunting muriquis and create incentives to protect them (Strier 1992a).

Threat: Changes in Native Species Dynamics

While habitat loss is a serious concern for muriqui populations, one side effect of fragmentation is the depletion or local extinction of predator species, many of which require large, continuous forests in which to hunt (González-Solís et al. 2001). Heavy predation pressure is therefore not a factor in conserving small, isolated subpopulations of muriquis (Lemos de Sá & Strier 1992).

Threat: Intrinsic Factors

One serious concern for animals living in small, fragmented populations that are isolated from each other is that inbreeding depression can make groups vulnerable to extinction. Low birth rates and high mortality rates characterize populations with limited gene flow and result in dwindling populations over time (Strier 2000). Furthermore, smaller populations with low genetic diversity are more vulnerable to stochastic events such as drought and disease outbreaks. While many muriqui populations are separated from each other and gene flow is limited, ill-effects have not been noted up to this point (Strier 1991; 1993/1994; 2000). For example, the muriquis at Montes Claros have been successfully reproducing and the group has steadily increased in size since Karen Strier began her work there in the early 1980s. With continued protection on private land and future forest regeneration on adjacent land, the population is projected to survive in the next 100 years (Strier 1993/1994).

Another intrinsic factor that may affect muriqui conservation is their slow rate of population growth which can be attributed to long interbirth intervals and late onset of sexual maturity and age at first parturition (Strier 1991b).

Potential Solutions

While the lower extinction probability for the population at Montes Claros is heartening, long-term viability of other muriqui populations cannot be extrapolated from their success. Further research is necessary to understand how small home ranges, fluctuations in habitat quality, and low population densities affect muriquis at other sites and ongoing efforts to secure contiguous primary or regenerating forest is necessary (Strier 2000). The size of the group at Montes Claros increased steadily as home ranges increased in association with forest regeneration and land protection (Strier 1991b; 1992a). If the data from Montes Claros can be applied to other study sights, the most important consideration for increasing population size is increasing available habitat.

In addition to land protection, intensive management of small populations may be necessary to avoid inbreeding depression. Translocation of muriquis between isolated forests would be one way to introduce new individuals to the breeding population and decrease the risk of close relatives mating. This process is risky for individual animals, and the costs should be weighed against the potential benefits (Strier 1992a).

Threat: Human Disturbance

Forest fires are rare in moist tropical forests, but the impact of logging and clearing of land can contribute to an unnaturally high risk of fires. While this has been greatly studied elsewhere in South America, there are no data regarding the impact of human-caused forest fires on muriquis (Chiarello 2003). At Montes Claros, Strier (1992a) documented one forest fire that was potentially catastrophic for the muriqui population when a fire used to clear land for a garden burned out of control. The threat of fires coupled with small populations means there is potential for even small forest fires to destroy entire muriqui populations.




Content last modified: August 30, 2006

Written by Kristina Cawthon Lang. Reviewed by Karen Strier.

Cite this page as:
Cawthon Lang KA. 2006 August 30. Primate Factsheets: Muriqui (Brachyteles) Conservation . <>. Accessed 2020 July 16.


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Content last modified: August 30, 2006



Brachyteles arachnoides
Photo: Luiz Claudio Marigo
Brachyteles arachnoides
Photo: Luiz Claudio Marigo

Brachyteles hypoxanthus
Photo: John Robinson
Brachyteles hypoxanthus
Photo: Luiz Claudio Marigo
Brachyteles hypoxanthus
Photo: Luiz Claudio Marigo
Brachyteles hypoxanthus
Photo: Luiz Claudio Marigo
Brachyteles hypoxanthus
Photo: Luiz Claudio Marigo
Brachyteles hypoxanthus
Photo: Luiz Claudio Marigo
Brachyteles hypoxanthus
Photo: Luiz Claudio Marigo
Brachyteles hypoxanthus
Photo: Luiz Claudio Marigo
Brachyteles hypoxanthus
Photo: Luiz Claudio Marigo
Brachyteles hypoxanthus
Photo: Luiz Claudio Marigo
Brachyteles hypoxanthus
Photo: Luiz Claudio Marigo
Brachyteles hypoxanthus
Photo: Luiz Claudio Marigo

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