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Spider monkeys of the genus Ateles are New World monkeys in the subfamily Atelinae, family Atelidae. Like other atelines, they are found in tropical forests of Central and South America, from southern Mexico to Brazil. The genus contains seven species, all of which are under threat; the Black-headed Spider Monkey and Brown Spider Monkey are critically endangered.

The disproportionately long limbs and long prehensile tail makes them one of the largest New World monkeys and gives rise to their common name. Spider monkeys live in the upper layers of the rainforest and forage in the high canopy, from 25 to 30 m (82 to 98 ft).^2] They primarily eat fruits, but will also occasionally consume leaves, flowers, and insects.^[2] Due to their large size, spider monkeys require large tracts of moist evergreen for ests and prefer undisturbed primary rainforest.^[2] They are social animals and live in bands of up to 35 individuals but will split up to forage during the day.^[3]

Recent meta-analyses on primate cognition studies indicated that spider monkeys are the most intelligent New World monkeys.^[4] They can produce a wide range of sounds and will 'bark' when threatened, other vocalisations include a whinny similar to a horse and prolonged screams.^[3]

They are an important food source due to their large size and are widely hunted by local human populations; they are also threatened by habitat destruction due to logging and land clearing.^[3] Spider monkeys are susceptible to malaria and are used in laboratory studies of the disease.^[3] The population trend for spider monkeys is decreasing; the IUCN Red List lists one species as vulnerable, four species as endangered and two species as critically endangered.

Evolutionary history

There are many theories about the evolution of the atelines; one theory is that spider monkeys are most closely related to the woolly spider monkeys (Bractyteles), and most likely split from the woolly monkeys (Lagothrix and Oreonax) in the South American lowland forest, to evolve their unique locomotory system.^[5] This theory is not supported by fossil evid ence. Other theories include Brachyteles, Lagothrix and Ateles in a non-resolved trichotomy,^[6] and two clades, one composed of Ateles and Lagothrix and the other of Alouatta and Brachyteles.^[7] More recent molecular evidence suggests that Atelinae split in the middle to late Miocene (13 Ma), separating spider monkeys from the woolly spider monkeys and the woolly monkeys.^[8]

Taxonomic classification

The genus contains seven species, and seven subspecies.^[1]

• Family Atelidae
  • Subfamily Alouattinae: howler monkeys
  • Subfamily Atelinae
    • Genus Ateles: spider monkeys
      • Red-faced Spider Monkey, Ateles p aniscus
      • White-fronted Spider Monkey, Ateles belzebuth
      • Peruvian Spider Monkey, Ateles chamek
      • Brown Spider Monkey, Ateles hybridus
      • White-cheeked Spider Monkey, Ateles marginatus
      • Black-headed Spider Monkey, Ateles fusciceps
        • Brown-headed Spider Monkey, Ateles fusciceps fusciceps
        • Colombian Spider Monkey, Ateles fusciceps rufiventris
      • Geoffroy's Spider Monkey, Ateles geoffroyi
        • Yucatan Spider Monkey, Ateles geoffroyi yucatanensis
        • Mexican Spider Monkey, Ateles geoffroyi vellerosus
        • Nicaraguan Spider Monkey, Ateles geoffroyi geoffroyi
        • Ornate Spider Monkey, Ateles geoffroyi ornatus
        • Hooded Spider Monkey, Ateles geoffroyi grisescens
    • Genus Brachyteles: woolly spider monkeys
    • Genus Lagothrix: woolly monkeys
    • Genus Oreonax: the Yellow-tailed Woolly Monkey
    < /ul>

  Anatomy and physiology

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  Geoffroy's Spider Monkey
  

  Spider monkey skeleton on display at The Museum of Osteology, Oklahoma City, Oklahoma.

  Spider monkeys are among the largest New World monkeys; Black-headed Spider Monkeys, the largest spider monkey, have an average weight of 10.8 kg (24 lb) for males and 9.66 0;kg (21.3 lb) for females.^[9][10] Disproportionately long, spindly limbs inspired the spider monkey's common name. Their deftly prehensile tails, which may be up to 89 cm (35 in) long, have very flexible, hairless tips and skin grooves similar to fingerprints. This adaptation to the spider monkey's strictly arboreal lifestyle serves as a fifth hand. When the monkey walks, its arms practically drag on the ground.^[11] Unlike many monkeys, they do not use their arms for balance when walking, instead relying on their tail.^[11] The hands are long, narrow and hook like, and have reduced thumbs.^[11] The fingers are elongated and recurved.^[11]

  The hair is coarse, ranging in color from ruddy gold to brown and black; the hands and feet are usually black. Heads are small with hairless faces. The nostrils are very far apart, which is a distinguishing feature of spider monkeys.^[12][13]

  Spider monkeys are highly agile, and they are said to be second only to the gibbons in this respect.

  Behavior

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  As is the case with all species of spider monkeys, the Brown Spider Monkey is threatened by hunting and habitat loss

  Spider monkeys form loose groups of 15 to 25 animals. During the day, groups break up into subgroups of 2 to 8 animals. This social structure ('fission-fusion') is found in only two other types of primates, chimpanzees and Homo sapiens. The size of subgroups and the degree to which they avoid each other during the day depends on food competition and the risk of predation. The average subgroup size is less than four animals.^[14] Also less common in primates, females rather than males disperse at puberty to join new groups. Males tend to stick together for their whole life. Hence males in a group are more likely to be related and have closer bonds than females. The strongest social bonds are formed between females and their young offspring.

  Spider monkeys communic ate their intentions and observations using postures and stances, such as postures of sexual receptivity and of attack. When a spider monkey sees a human approaching, it barks loudly similar to a dog. When a monkey is approached, it climbs to the end of the branch it is on and shakes it vigorously to scare away the possible threat. It shakes the branches with its feet, hands, or a combination while hanging from its tail. It may also scratch its limbs or body with various parts of its hands and feet. Seated monkeys may sway and make noise. Males and occasionally adult females growl menacingly at the approach of a human. If the pursuer continues to advance, the monkeys often break off live or dead tree limb weighing up to 4 kg and drop them towards the intruder. They do not actually throw the branches, but twist to cause the branch to fall closer to the threat.^{[clarification needed]} The natives of the area know very well of this risk. The monkeys also defecate and urinate toward the intruder.^[15]

  Spider monkeys are diurnal and spend the night sleeping in carefully selected trees. Groups are thought to be directed by a lead female who is responsible for planning an efficient feeding route each day. Grooming is not as important to social interaction, owing perhaps to a lack of thumbs.

  Spider monkeys have been observed avoiding the upper canopy of the trees for locomotion. One researcher speculated that this was because the thin branches at the tops of trees do not support the monkeys as well.^[16]

  At 107 grams, the spider monkey brain is twice the size of a howler monkey brain of equivalent body size; this is thought to be a result of the spider monkeys' complex social system and their frugivorous diet, which consists primarily of ripe fruit from a wide varie ty (over 150 species) of plants. This requires the monkeys to remember when and where fruit can be found. The slow development may also play a role: the monkeys may live 20 years or more, and females give birth once every 3 to 4 years.

  Feeding

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  The diet of spider monkeys consists of about 90% fruits and nuts. They can live for long periods on only one or two kinds of fruits and nuts. They eat the fruits of many big forest trees, and because they swallow fruits whole, the seeds are eventually excreted and fertilized by the feces. Studies show the diet of spider monkeys changes their reproductive, social, and physical behavioral patterns. Most feeding happens from dawn to 10 am. Afterward, the adults rest while the young play. Through the rest of the day they may feed infrequently until around 10 pm. If food is low they may eat insects, bark and honey.

  Spider monkeys have a unique way of getting food: a lead female is generally responsible for finding food sources. If she cannot find enough food for the group, it splits into smaller groups that forage separately.^[17] The traveling groups have four to nine animals. Each group is closely associated with its territory.^[18] If the group is big, it spreads out.

  Reproduction

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  The female chooses a male from her group with whom to mate. Both males and females sniff their mates to check their readiness for copulation. This process is known as ?anogenital sniffing?. The gestation period ranges from 226 to 232 days. Each female bears only one offspring on average, every 3 to 4 years.

  Until six to ten months, infants rely completely on their mother.^[15] Males are not involved in rais ing the offspring.

  A mother carries her infant around her belly for the first month after birth. After this she carries it on her lower back. The infant wraps its tail around its mother?s and tightly grabs her midsection. Mothers are very protective of their young and are generally attentive mothers. They have been seen grabbing their young and putting them on their backs for protection and to help them navigate from tree to tree. They help the more independent young to cross by pulling branches closer together. Mothers also groom their young.

  form loose groups of 15 to 25 animals. During the day, groups break up into subgroups of 2 to 8 animals. This social structure ('fission-fusion') is found in only two other types of primates, chimpanzees and Homo sapiens. The size of subgroups and the degree to which they avoid each other during the day depends on food competition and the risk of predation. The average subgroup size is less than four animals.^[14] Also less common in primates, females rather than males disperse at puberty to join new groups. Males tend to stick together for their whole life. Hence males in a group are more likely to be related and have closer bonds than females. The strongest social bonds are formed between females and their young offspring.

  Spider monkeys communicate their intentions and observations using postures and stances, such as postures of sexual receptivity and of attack. When a spider monkey sees a human approaching, it barks loudly similar to a dog. When a monkey is approached, it climbs to the end of the branch it is on and shakes it vigorously to scare away the possible threat. It shakes the branches with its feet, hands, or a combination while hanging from its tail. It may also scratch its limbs or body with various parts of its hands and feet. Seated monkeys may sway and make noise. Males and occasionally adult females growl menacingly at the approach of a human. If the pursuer co ntinues to advance, the monkeys often break off live or dead tree limb weighing up to 4 kg and drop them towards the intruder. They do not actually throw the branches, but twist to cause the branch to fall closer to the threat.^{[clarification needed]} The natives of the area know very well of this risk. The monkeys also defecate and urinate toward the intruder.^[15]

  Spider monkeys are diurnal and spend the night sleeping in carefully selected trees. Groups are thought to be directed by a lead female who is responsible for planning an efficient feeding route each day. Grooming is not as important to social interaction, owing perhaps to a lack of thumbs.

  Spider monkeys have been observed avoiding the upper canopy of the trees for locomotion. One researcher speculated that this was because the thin branches at the tops of trees do not supp ort the monkeys as well.^[16]

  At 107 grams, the spider monkey brain is twice the size of a howler monkey brain of equivalent body size; this is thought to be a result of the spider monkeys' complex social system and their frugivorous diet, which consists primarily of ripe fruit from a wide variety (over 150 species) of plants. This requires the monkeys to remember when and where fruit can be found. The slow development may also play a role: the monkeys may live 20 years or more, and females give birth once every 3 to 4 years.

  Feeding

  [ Back to top ]

  The diet of spider monkeys consists of about 90% fruits and nuts. They can live for long periods on only one or two kinds of fruits and nuts. They eat the fruits of many big forest trees, and because they swallow fruits whole, the seeds are eventually excreted and fertilized by the feces. Studies show the diet of spide r monkeys changes their reproductive, social, and physical behavioral patterns. Most feeding happens from dawn to 10 am. Afterward, the adults rest while the young play. Through the rest of the day they may feed infrequently until around 10 pm. If food is low they may eat insects, bark and honey.

  Spider monkeys have a unique way of getting food: a lead female is generally responsible for finding food sources. If she cannot find enough food for the group, it splits into smaller groups that forage separately.^[17] The traveling groups have four to nine animals. Each group is closely associated with its territory.^[18] If the group is big, it spreads out.

  Reproduction

  [ Back to top ]

  The female chooses a male from her group with whom to mate. Both males and females sniff their mates to check their re adiness for copulation. This process is known as ?anogenital sniffing?. The gestation period ranges from 226 to 232 days. Each female bears only one offspring on average, every 3 to 4 years.

  Until six to ten months, infants rely completely on their mother.^[15] Males are not involved in raising the offspring.

  A mother carries her infant around her belly for the first month after birth. After this she carries it on her lower back. The infant wraps its tail around its mother?s and tightly grabs her midsection. Mothers are very protective of their young and are generally attentive mothers. They have been seen grabbing their young and putting them on their backs for protection and to help them navigate from tree to tree. They help the more independent young to cross by pulling branches closer together. Mothers also groom their young.

  References

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  1. ^ ^{a b} Groves, C. (2005). Wilson, D. E.; Reeder, D. M. eds. Mammal Species of the World (3rd ed.). Baltimore: Johns Hopkins University Press. pp. 150?151. OCLC 62265494. ISBN 0-801-88221-4. http://www.bucknell.edu/msw3/browse.asp?id=12100392. 
  2. ^ ^{a b c} Ca wthon Lang, KA (2007-04-10). "Primate Factsheets: Black spider monkey (Ateles fisciceps) Taxonomy, Morphology, and Ecology". Wisconsin Primate Research Center (WPRC). http://pin.primate.wisc.edu/factsheets/entry/black_spider_monkey. Retrieved 2009-05-20. 
  3. ^ ^{a b c d} "Spider monkey". Encyclop?dia Britannica Online. Encyclop?dia Britannica, Inc.. 2009. http://www .britannica.com/EBchecked/topic/559849/spider-monkey. Retrieved 2009-05-20. 
  4. ^ Deaner, R.O., van Schaik, C.P. and Johnson, V.E. (2006). "Do some taxa have better domain-general cognition than others? A meta-analysis". Evolutionary Psychology 4: 149?196. http://www.epjournal.net/filestore/ep04149196.pdf. 
  5. ^ Kinzey, W. G. (1997). New world primates: ecology, evolution, and behavior. Aldine Transaction. ISBN 0202011860. 
  6. ^ Ford, S. M. (1986). "Systematics of the New World monkeys". In Swindler, D. R. & Erwin, J.. Comparative Primate Biology, Volume I: Systematics, Evolution and Anatomy. New York: Alan R. Liss. pp . 73?135. 
  7. ^ Kay, R. F. (1990). "The phyletic relationships of extant and fossil Pitheciinae (Platyrrhini, Anthropoidea)". Journal of Human Evolution 19: 175?208. doi:10.1016/0047-2484(90)90016-5. 
  8. ^ Schneider, H. (2000). "The Current Status of the New World Monkey Phylogeny". Anais da Academia Brasileira de Ci?ncias 72 (2): 165. doi:10.1590/S0001-37652000000200005. http://www.scielo.br/scielo.php?pid=S0001-37652000000200005&script=sci_arttext&tlng=en. Retrieved 2009-05-20 . 
  9. ^ Youlatos, D. (2002). "Positional behavior of black spider monkeys (Ateles paniscus) in French Guiana". International Journal of Primatology 23 (5). 
  10. ^ Di Fiore, A. & Campbell, C. J. (2007). "The atelines: variation in ecology, behavior, and social organization". In Campbell, C. J., Fuentes, A., MacKinnon, K. C., Panger, M. & Bearder, S.K.. Primates in perspective. New York: Oxford University Press. pp. 155?85. 
  11. ^ ^{a b c d} "Spider Monkey". Brevard Zoo. 2009. http://www.brevardzoo.org/explore_selva.php?id=119. Retrieved 2009-07-29. 
  12. ^ "Spider Monkey". Honolulu Zoo. http://www.honoluluzoo.org/spider_monkey.htm. Retrieved 2008-04-07. 
  13. ^ "Ateles geoffroyi". Animal Diversity Web. http://www.animaldiversity.ummz.umich.edu/site/accounts/information/Ateles_geoffroyi.html. Retrieved 2007-10-02. 
  14. ^ http://www.honoluluzoo.org/spider_monkey.htm
  15. ^ ^{a b} Carpenter, C.R. (August 1935). "Behavior of Red Spider Monkeys in Panama". Journal of Mammalogy 16 (3): 171?180. doi:10.2307/1374442. JSTOR 1374442. 
  16. ^ Allen, William (English cardinal). "On standby for the new ark: if spider monkeys are chosen to ride out the 'demographic winter,' here is what latter-day Noahs will have to know." The Sciences 34.n5 (Sept-Oct 1994): 15(3). Expanded Academic ASAP. Gale. BENTLEY UPPER SCHOOL LIBRARY (BAISL). 6 Oct. 2009 http://find.galegroup.com/gtx/start.do?prodId=EAIM
  17. ^ "Spider Monkey: Cebidae Anteles Geoffroyi geoffroyi". Zoo School. http://www.zooschool.ecsd.net/spider%20monkey.htm. Retrieved 2007-10-09. 
  18. ^ Gordon, Nick. "The Spider Monkey and the Rainforest". BBC Wildlife Magazine ? Monkey business. Archived from the original on 2007-07-12. http://web.archive.org/web/20070712231913/http://www.bbc.co.uk/nature/animals/features/192index.shtml. Retrieve d 2007-10-05. 

  External links

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  • Black Spider Monkey (Ateles paniscus)
  • Primate Info Net Ateles Factsheets