Geographic Range
Brown spider monkeys,
Ateles hybridus
, are restricted to subtropical and tropical moist lowlands in Venezuela and Colombia.
There are two recognized subspecies of
A. hybridus
,
Ateles hybridus hybridus
and
Ateles hybridus brunneus
. The former occurs in both Colombia and Venezuela, inhabiting forests from the right
bank of the RÃo Magdalena to areas extending into western parts of Venezuela.
Ateles hybridus brunneus
can only be found in Colombia, ranging between the lower RÃos Cauca and Magdalena
in the Departments of BolÃvar, Antioquia, and Caldas.
- Biogeographic Regions
- neotropical
Habitat
Brown spider monkeys are arboreal and mainly found in high and lowland primary evergreen
rainforest from 20 to 700 m elevation. They spend most of their time traveling and
foraging in the high canopy, but they also use the middle and lower strata to a lesser
extent. They rarely descend to the forest floor except for drinking water or eating
soil.
Brown spider monkeys are habitat specialists and prefer undisturbed old forests (primary
forests) and rarely inhabit disturbed forests with less complete canopy (secondary
forests). Primary forests have tall mature trees, a continuous canopy, an understory
with little underbrush and significant bigger and more abundant fruiting trees than
secondary forests have. One reason for their habitat choice is that their diet primarily
consists of fruit.
- Habitat Regions
- tropical
- terrestrial
- Terrestrial Biomes
- rainforest
Physical Description
The appearance of
Ateles hybridus
is similar to other species of
spider monkeys
and, as their common name indicates, spider monkeys have exceptionally long, slender
limbs. Their forelimbs are longer than their hindlimbs and their intermembral index
is approximately 105. They also have a long, thin, prehensile tail, which acts almost
like a fifth limb. These features enable them to be highly suspensory and allow them
to easily forage and travel in the high canopy. The length of the tail is around 75
cm and is highly flexible and distally hairless, with ridged skin for a better grip.
The hands are hook-like, with four elongated, curved, fingers. The thumb is reduced,
which facilitates swinging and gripping branches and is an adaptation to their strictly
arboreal lifestyle.
Spider monkeys
are the biggest of all the New World primates, an adult male brown spider monkey
weighs between 7.9 and 9.1 kg and an adult female weighs between 7.5 and 9 kg. The
average body length for adult individuals is around 50 cm. Their coloration ranges
from light brown to dark on upper parts including the head. The inner side of the
legs, arms and tail are a lighter, more buff color. Another distinguishing characteristic
of this species is the white triangular forehead patch but not all individuals possess
this conspicuous feature. Some individuals also have pale blue eyes, but usually they
are light brown.
- Other Physical Features
- endothermic
- homoiothermic
- bilateral symmetry
- Sexual Dimorphism
- male larger
Reproduction
The mating system of brown spider monkeys is not well studied, but is most likely
similar to that of other members of
Atelinae
which are polygynandrous, where each individual mates with multiple partners. All
copulations are initiated by the female, which indicates a high level of female mate
choice and might lead to reduced aggression in males. Females in this genus copulate
with many males over a period of time; this might be a female strategy to prevent
infanticide by causing paternity confusion. However, intragroup infanticide by other
males has been observed, although not reported for this particular species. Mating
is not seasonal and no precopulatory rituals have been observed in spider monkeys.
- Mating System
- polygynandrous (promiscuous)
Similar to the other species of spider monkeys,
Ateles hybridus
is characterised by a slow reproductive rate, with females usually giving birth to
a single offspring every 3 to 4 years. Although not reported for this particular species,
intragroup infanticide by males has been observed in other spider monkey species which
shortens the interbirth interval. In captivity the birth interval of brown spider
monkeys can be reduced to a minimum of 1.5 years and they do not show seasonality
in their births. Wild populations, however, show a low grade of seasonality, with
a higher birth rate at the beginning of the rainy season, May to July, when fruits
are more abundant. The species typically reaches sexual maturity at 4 to 5 years of
age and females give birth to their first infant at an age of 7 to 8 years.
- Key Reproductive Features
- iteroparous
- year-round breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- fertilization
- viviparous
The gestation period is approximately 226 to 232 days. When offspring are born they
cling to their mother’s belly the first couple of months, and then climb over to her
back. Young lactate at least one year. In captive spider monkeys, however, lactation
has been seen up to twenty months. Females provide the major part of the parental
care and very strong social bonds are formed between females and their offspring.
During the dependent period, which is approximately 18 months, the offspring gets
protection as well as an extended period of learning, where the offspring learns everything
from social to foraging behaviors.
- Parental Investment
- altricial
-
pre-fertilization
- provisioning
-
protecting
- female
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-independence
-
provisioning
- female
-
protecting
- female
-
provisioning
- post-independence association with parents
- extended period of juvenile learning
Lifespan/Longevity
The average life span for spider monkeys is approximately 27 years in the wild. In
captivity, on the other hand, they can live to be 10 years old or more.
Behavior
Ateles hybridus
is a diurnal and very social species, living in multi-female, multi-male groups.
They live in fission-fusion societies in which subgroups of varying size and composition
are formed during the day, ranging from 2 to 30 members. Among primates generally,
this fission- fusion structure is mainly found in spider monkeys (
Ateles
) and chimpanzees (
Pan
).
There are no clear hierarchies in spider monkeys although there might be subtle rankings
determined by age. In brown spider monkeys, however, this is neither found in males
nor in females (Link. pers. comm. 2009).
Males usually travel in all-male groups and females with their dependent offspring,
although it is not unusual for individuals to travel and forage alone.
At night brown spider monkeys use sleeping trees that are usually emergent trees in
close proximity to a food source (fruit trees), so they won’t have to travel far the
next day to find food. Since the sleeping sites are high up, above the canopy, they
also provide a secure place from potential predators. There are differences in group
size related to fruit availability. During periods when fruit is abundant, females
tend to associate with each other more, thus increasing the size of the group. In
periods when fruits are scarcer, groups are smaller. The same pattern is found in
male groups. Larger groups also tend to form when they descend to the ground to drink
water or eat soil. They may be because some individuals watch out for predators while
rest of the individuals are drinking.
Male spider monkeys are the philopatric sex, staying in the natal group. Females disperse
at puberty to join new groups. Since males are philopatric, they are more likely to
be related and tend to be more social and interact more frequently with each other
than females do.
Home Range
Brown spider monkey home range is estimated to encompass 259 to 388 ha. Males travel
through a more extended area than females. Spider monkeys do not use the whole area
of their home range evenly, but use special paths when traveling and foraging.
Communication and Perception
Brown spider monkeys frequently use a wide variety of calls to keep contact with each
other and to locate other subgroups. They use so called whinnies, i.e. loud calls
mostly, which bring information about location and identity of the emitter, but they
also use ‘ts chookis’, whoops, wails and screams. The latter can be heard over long
distances. Alarm calls are also used when predators are nearby.
Tactile communication occurs in the form of grooming. This is an infrequent behavior
in spider monkeys and some claim that it is due to the absent thumb. Ahumada (1992)
found that
Ateles geoffroyi
individuals allocated only 2.5% of their daily activity to grooming, mostly adult
females groom their offspring or other juveniles, but male-male grooming occurs as
well.
Brown spider monkeys have good eye sight and excellent color vision, which is important
for detecting and selecting ripe fruits from unripe ones, but is also used for the
detecting predators, as well as for communicating with conspecifics. Visual signals
such as head shaking, arm and chest scratching as well as tooth exposure are used
in antagonistic and threat situations.
Olfactory behaviors are used in sexual contexts, in which chest-rubbing and pectoral
gland sniffing occur. Female spider monkeys also use their over-sized clitoris to
deposit drops of urine as scent marks.
- Other Communication Modes
- scent marks
Food Habits
Brown spider monkeys are highly frugivorous and feed on a wide variety of fruits all
year round. They specialize on ripe fruit, which comprises approximately 83% of their
diet. A large part of their fruit intake consists of lipid rich fruits in the families
Arecaceae
,
Lauraceae
,
Meliaceae
and
Myristicaceae
. However, their dietary composition is dependent on seasonal variation in fruit abundance.
When fruits are less abundant during dryer seasons they complement their diet with
young leaves and flowers, young seeds, bark, honey, decaying wood, and sometimes even
termites and caterpillars. Brown spider monkeys forage mainly in emergent trees and
upper part of the forest canopy and rely heavily on vision to recognize food items,
but also use olfactory, gustatory, and tactile cues to a lesser extent.
Figs
of different species are a very important food resource, which spider monkeys feed
on all year around. They have also been observed eating soil and clay. Several hypotheses
to why this might be have been put forward, from the importance of the high mineral
content in the soil, to the need for phosphorus and the need to keep an even pH- balance
in their digestive system. Spider monkeys also descend to the forest floor to drink
water at so called salado sites, and it is hypothesized that their water consumption
is a consequence of their high intake of lipid rich fruits. Interspecific feeding
competition occurs between spider monkeys and other frugivorous primates, for example
woolly monkeys
,
howler monkeys
,
squirrel monkeys
, and
other New World monkeys
.
- Animal Foods
- insects
- Plant Foods
- leaves
- roots and tubers
- wood, bark, or stems
- fruit
- nectar
- pollen
- flowers
Predation
Because of the large body size of
Ateles hybridus
, the only significant potential predators on adult individuals are thought to be
jaguars and pumas. Matsuda and Izawa (2008) report predation attempts by a jaguar
(
Panthera onca
) and a puma (
Puma concolor
) on an adult female of the spider monkey species
Ateles belzebuth
. However, babies and juveniles are susceptible to predators like harpy eagles (
Harpia harpyja
), crested eagles (
Morphnus guianensis
), and smaller carnivores.
Poaching also poses a major threat to
Ateles hybridus
, they are subject to both subsistence and commercial hunting. They are primarily
hunted for meat, but hunting for the pet trade is not unusual. In pet trade situations
the female is killed and the baby is kept and sold.
Ecosystem Roles
Studies of seed dispersal by spider monkeys have shown that they play an important
role in the maintenance of neotropical rain forest diversity, both through endozoochory
and exozoochory. Endozoochory is when the animal disperses the fruit's seeds within
the body of the animal, as they swallow the seeds and they pass through the animal's
digestive system. Exozoochory is when the animal disperses seeds by carrying them
off from the tree to another location and drop them. Link and Di Fiore (2006) found
that
Ateles belzebuth
swallowed 98% of the seeds from the approximately 152 different plant species that
the monkeys fed on. They also found that monkeys appear to be particularly important
dispersers for plants producing large seeded fruits or those protected by thick husks,
many of which other frugivorous species cannot eat. An individual spider monkey dispersed
a minimum of 195,000 seeds per year which were bigger than 1 mm in diameter and 35,000
seeds bigger than 3 mm in diameter. The longest distance seeds were moved was 1.2
km, though the average distance was 443 m from the parental source. The results of
Link and Di Fiore (2006) and Stevenson and Aldana (2008) show that spider monkeys
play a significant role as seed dispersers and that a population decline could have
a big and direct impact on forest dynamics, particularly if other disperser species
cannot compensate for their lost ecological services. Furthermore, it is possible
that their fission–fusion social structure and ranging behavior also influence their
pattern of seed dispersal. The fact that they split up in subgroups while foraging
could generate a more scattered distribution of defecated seed across the habitat,
compared with species that ranges in more cohesive groups. This ranging pattern of
spider monkeys could in turn have positive effects on growing rates and survival of
the seeds.
- Ecosystem Impact
- disperses seeds
Economic Importance for Humans: Positive
Brown spider monkeys are critical members of the rainforest ecosystems they live in,
they are important for forest regeneration through seed dispersal.
Economic Importance for Humans: Negative
There are no known adverse effects of Ateles hybridus on humans.
Conservation Status
Both of the subspecies of
Ateles hybridus
are listed as Critically Endangered on IUCN Red List and are listed in IUCN's “world’s
25 most endangered primates." The biggest threats to their populations are forest
fragmentation and degradation, as well as the pet trade and illegal hunting. Large
proportions of
A. hybridus
habitats have been converted to lands for agriculture and a lot of the remaining
habitats are surrounded by human populations and roads. Only 0.67% of their distribution
is protected, so there is a urgent need for protected areas and national parks, which
also could include two other threatened endemic primates, white footed tamarins (
Saguinus leucopus
) and woolly monkeys (
Lagothrix lugens
). As mentioned in the habitat section,
A. hybridus
prefers continuous, secondary forests, but only 9% of
Ateles h. brunneus
potential range remains in that condition.
The large body size of A. hybridus and their slow reproductive rate, with late maturation
and long interbirth intervals, constrain them from recovering from population declines
and make them more vulnerable to extinction.
A combination of ex-situ, in-situ, and education projects is necessary to protect
this endangered species. To estimate the density and distribution for this species
is also a priority research topic for conservation purposes. Protected areas are necessary
for their survival as well as breeding programs for captive animals. Also surveys
are much needed to establish population densities of some of the subspecies and to
determine local threats.
Brown spider monkeys possess all of the natural history characteristics that accompany
higher risk of extinction: large body size, slow reproductive rate, being a food specialist,
having a large home range, long life span, late maturation, and long interbirth intervals.
All this constrains the species from recovering from population declines, and make
them more vulnerable to extinction. The large-scale fragmentation and deforestation
of rainforest is a direct threat to
A.hybridus
as secondary forest is unsuitable as habitat for them.
A. hybridus
inhabit fragmented habitats and we know suprisingly little about the processes that
underpin survival in fragmented habitats. Small- population effects might be too serious
to be reversed. It would be unfortunate to lose a species that we still know so little
about. We have just begun to understand aspects of their behavior and ecology. Further
studies would increase our understanding of, for example, their complex social structure
and hierarchies.
Additional Links
Contributors
Maria Thunstrom (author), University of Oregon, Stephen Frost (editor, instructor), University of Oregon, Tanya Dewey (editor), Animal Diversity Web.
- Neotropical
-
living in the southern part of the New World. In other words, Central and South America.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- terrestrial
-
Living on the ground.
- rainforest
-
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
- endothermic
-
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- polygynandrous
-
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
- iteroparous
-
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
- year-round breeding
-
breeding takes place throughout the year
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- fertilization
-
union of egg and spermatozoan
- viviparous
-
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- altricial
-
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
- arboreal
-
Referring to an animal that lives in trees; tree-climbing.
- diurnal
-
- active during the day, 2. lasting for one day.
- motile
-
having the capacity to move from one place to another.
- nomadic
-
generally wanders from place to place, usually within a well-defined range.
- sedentary
-
remains in the same area
- territorial
-
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
- social
-
associates with others of its species; forms social groups.
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- scent marks
-
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- herbivore
-
An animal that eats mainly plants or parts of plants.
- frugivore
-
an animal that mainly eats fruit
References
Ahumada, J. 1992. Grooming Behavior of Spider Monkeys (Ateles geoffroyi) on Barro Colorado Island, Panama. International Journal of Primatology , 13: 33-49.
Ankel-Simons, F. 1999. Primate Anatomy: An Introduction. 2nd Ed . San Diego: Academic Press.
Chapman, C., D. Onderdonk. 1998. Forests without primates: Primate/Plant codependency. American Journal of Primatology , 45: 127-141.
Collins, A., J. Dubach. 2000. Phylogenetic relationships among spider monkeys (Ateles): Based on mitochondrial DNA variation. International Journal of Primatology , 21: 381–420.
Cowlishaw, G., R. Dunbar. 2000. Primate Conservation Biology . Chicago: The University of Chicago Press.
Fleagle, J. 1999. Primate Adaptation and Evolution 2nd Ed. . San Diego: Academic Press.
Groves, C. 2005. Ateles hybridus. Pp. 151 in Mammal Species of the World (3rd edition ed.) . Washington, DC: Johns Hopkins University Press.
Link, A., A. Di Fiore. 2006. Seed dispersal by spider monkeys and its importance in the maintenance of neotropical rain-forest diversity. Journal of Tropical Ecology , 22: 235–246.
Link, A., A. Morales Jimenez. 2008. " http://www.fundacionbiodiversa.org/ " (On-line pdf). Accessed January 19, 2008 at www.fundacionbiodiversa.org/pdf/Ateles/EcologyQuinchasReport.pdf .
Matsuda, I., K. Izawa. 2008. Predation of wild spider monkeys at La Macarena, Colombia. Primates , 49: 65-68.
Mittermeier, R., J. Ratsimbazafy, A. Rylands, L. Williamson, J. Oates. 2008. Primates in Peril: The World’s 25 Most Endangered Primates 2006–2008. Primate Conservation , 22: 1-40.
Morales Jiménez, A. 2007. "Action Plan of the spider monkeys Ateles hybridus and Ateles fusciceps in Colombia" (On-line pdf). Accessed January 12, 2009 at http://www.fundacionbiodiversa.org/pdf/Ateles/Atelesactionplanweb.pdf .
Palacios, E., A. Morales-Jiménez. 2007. "Variegated or Brown Spider Monkey, Ateles hybridus I. Geoffroy, 1829." (On-line). Accessed January 13, 2009 at http://www.primate-sg.org/hybridus07.htm .
Stevenson, P., A. Aldana. 2008. Potential Effects of Ateline Extinction and Forest Fragmentation on Plant Diversity and Composition in the Western Orinoco Basin, Colombia.. International Journal of Primatology , 29: 365–377.
Takahashi, J. 2008. "A literature review of the spider monkey, Ateles sp., with special focus on risk for extinction" (On-line pdf). Accessed January 12, 2009 at http://ex-epsilon.slu.se/archive/00002758/01/EXJOBB_TRYCK.pdf .
Urbani, B., A. Morales, A. Link, P. Stevenson. 2008. "www.iucnredlist.org" (On-line). The IUCN Red list of threatened species. Accessed January 12, 2009 at http://www.iucnredlist.org .