Critically endangered (B. hypoxanthus), Endangered (B. arachnoides)
Life span: Unknown
Total population: 700 (wild)
Gestation: 7.2 months (216 days)
Height: 490 mm (M), 486 mm (F)
Weight: 9.6 kg (M), 8.4 kg (F)
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
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
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
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).
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
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
Among southern muriquis, the external thumb is entirely missing while in
northern muriquis, there is a
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:
climbing and rapid
(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).
CURRENT RANGE MAPS (IUCN REDLIST):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
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 (www.isis.org).
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
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
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).
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.
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).
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).
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).
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
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 . <http://pin.primate.wisc.edu/factsheets/entry/muriqui/taxon>. Accessed 2014 September 2.