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Lifespan, longevity, and ageing

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Observations: Not much is known about the longevity of these animals. One specimen was about 18 years old when it died in captivity (Richard Weigl 2005). Considering the longevity of similar species, maximum longevity is likely much longer, though.
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Morphology

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Saimiri oerstedii is a small, slender monkey with a long tail (Reid, 1997). Much of their body fur is yellow brown in color with a pale yellow belly (Reid, 1997). Saimiri oerstedii can be distinguished from its sister species Saimiri sciureus because the crown of S. oerstedii is covered with black fur while that of S. sciureus is not (Chiarelli, 1972). Also, S. oerstedii has golden-red colored fur on its back (Rosenblum and Coe, 1985). Saimiri oerstedii weighs between 500 and 1100 g (Reid, 1997). Squirrel monkeys are typically 225 to 295 mm long with tails adding between 370 and 465 mm (Chiarelli, 1972).

Range mass: 500 to 1100 g.

Range length: 225 to 295 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

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Ambrose, T. 2002. "Saimiri oerstedii" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Saimiri_oerstedii.html
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Thomas Ambrose, University of Michigan-Ann Arbor
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Habitat

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Little information is available about the habitat of S. oerstedii. In general, squirrel monkeys are arboreal and can be found in primary and secondary forests (Nowak, 1999), thickets, and mangrove swamps (Macdonald, 1984). They are also found in cultivated areas, usually around streams (Nowak, 1999). Saimiri oerstedii is known to inhabit humid Pacific slope forests (Reid, 1997).

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: forest ; rainforest

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Ambrose, T. 2002. "Saimiri oerstedii" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Saimiri_oerstedii.html
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Thomas Ambrose, University of Michigan-Ann Arbor
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Distribution

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Saimiri oerstedii inhabits parts of the Pacific coast of Panama and Costa Rica (Nowak, 1999).

Biogeographic Regions: neotropical (Native )

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Ambrose, T. 2002. "Saimiri oerstedii" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Saimiri_oerstedii.html
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Thomas Ambrose, University of Michigan-Ann Arbor
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Trophic Strategy

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The diet of S. oerstedii consists mostly of invertebrates, small vertebrates, fruit, and flower nectar (Reid 1997). They also recognize the leaf-tents made by some fruit-eating bats and attack these tents to extract the bats (Reid 1997).

In general, members of the genus Saimiri feed primarily on fruit, berries, seeds, gums, leaves, buds, insects, arachnids and small vertebrates (Nowak, 1999). Nearly half of their diet is made up of fruit (Smuts et al., 1987). Most of their prey are immobile invertebrates (Smuts et al., 1987). When the animals find food in a tree, they often do not completely use up the resources available and may return to it in the future (Parker, 1990).

Animal Foods: insects; terrestrial non-insect arthropods

Plant Foods: leaves; seeds, grains, and nuts; fruit; nectar; sap or other plant fluids

Primary Diet: omnivore

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Ambrose, T. 2002. "Saimiri oerstedii" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Saimiri_oerstedii.html
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Thomas Ambrose, University of Michigan-Ann Arbor
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Benefits

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Squirrel monkeys in general (not specifically S. oerstedii) do benefit humans in that they are very widely used in biomedical research (Strier, 2000). Half of all squirrel monkeys imported to the United States in 1968 were used in labs while the other half were used in zoos and the pet trade (Nowak, 1999). They are often used for aerospace research as well (Rosenblum and Cooper, 1968). In the past, they have also been kept as pets for the European and American aristocracy (Hearn, 1983).

Positive Impacts: pet trade ; research and education

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Ambrose, T. 2002. "Saimiri oerstedii" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Saimiri_oerstedii.html
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Thomas Ambrose, University of Michigan-Ann Arbor
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Conservation Status

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Although its sister species, S. sciureus, is quite abundant the IUCN places S. oerstedii on the endangered list (Nowak, 1999). The population has declined drastically with the destruction of forest habitats (Nowak, 1999). While abundant in the regions it inhabits, S. oerstedii is restricted to a very small area ( Smuts et al., 1987).

CITES: appendix i

IUCN Red List of Threatened Species: vulnerable

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Ambrose, T. 2002. "Saimiri oerstedii" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Saimiri_oerstedii.html
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Thomas Ambrose, University of Michigan-Ann Arbor
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Behavior

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Perception Channels: tactile ; chemical

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Ambrose, T. 2002. "Saimiri oerstedii" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Saimiri_oerstedii.html
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Thomas Ambrose, University of Michigan-Ann Arbor
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Untitled

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There have been some difficulties in finding information on S. oerstedii due to its rarity. In general, it is believed to be very similar to its sister species, S. sciureus (Moynihan, 1976). Also, the taxonomy of the genus is not completely resolved. Some authors divide Saimiri into two species, S. sciureus and S. oerstedii (Parker, 1990) while others see between five species (Nowak, 1999) and only one species which can be divided into two subspecies (Moynihan 1976).

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Ambrose, T. 2002. "Saimiri oerstedii" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Saimiri_oerstedii.html
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Thomas Ambrose, University of Michigan-Ann Arbor
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Reproduction

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The birth rate in the genus Saimiri is about one birth per year (no information specifically for S. oerstedii). Females do not resume cycling until their infant either dies or is weaned (Smuts et al., 1987). The infants are usually born at night (Parker, 1990). Females of S. oerstedii give birth to one young after a gestation period of 7 months (Reid, 1997). The births usually occur during the wet season (Reid, 1997). Although no data were available S. oerstedii, females of its sister species Saimiri sciureus are in a period of estrous around 12 to 36 hours (Hayssen et al., 1993)

Females are sexually mature at about 1 year old, males reach sexual maturity between 4 and 6 years old.

Breeding interval: The birth rate in the genus Saimiri is about one birth per year

Average number of offspring: 1.

Average gestation period: 7 months.

Average age at sexual or reproductive maturity (female): 1 years.

Average age at sexual or reproductive maturity (male): 4-6 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous

Average number of offspring: 1.

In general, a Saimiri mother takes care of the young although sometimes other females help (Parker, 1990). These females are sometimes referred to as "aunts" (Parker, 1990).

For the first few weeks of its life, an infant of genus Saimiri, probably including S. oerstedii, rides along on its mother's back and nurses, with little attention paid to it by the group members (Parker, 1990). During its third and fourth weeks of life, the young monkey begins to move around more and between weeks five and ten, it occasionally disembarks from its mother's back, explores the nearby area, and starts to eat solid foods (Parker, 1990). Over the next couple of months, contacts with the mother become less frequent (Parker, 1990).

In other Saimiri (S. oerstedii is poorly studied), social play first occurs around two months (Parker, 1990). Social play serves to help separate the infant from its mother (Macdonald, 1984). In the first year of life, the young monkeys engage in social play with each other, usually in the form of fighting games (Parker, 1990). Females become adult around month twelve to thirteen while males achieve maturation around their fourth or sixth year (Parker, 1990).

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Protecting: Female); extended period of juvenile learning

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Ambrose, T. 2002. "Saimiri oerstedii" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Saimiri_oerstedii.html
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Thomas Ambrose, University of Michigan-Ann Arbor
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Biology

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Little is known about the biology of this species. Like other squirrel monkeys it is active during the day and is arboreal (6). This small primate is omnivorous and spends most of the morning and afternoon foraging in the trees for fruits, leaves, buds, gums, insects and small vertebrates (7). It has been reported that this species recognises the leaf-tents constructed by some fruit-eating bats and attacks these structures to extract the bats roosting within (8). Red-backed squirrel monkeys are social primates. They live in large multi-male / multi –female groups of about two-dozen individuals on average, and travel between 2.5 and 4.2 km a day, with home ranges of 0.175 km² (2) (6) (9). Reproduction is seasonal, with mating occurring in January and February (2), with single births occurring at the period of greatest food availability. This ensures there will be adequate food available for the mothers and their young, and requires less time spent foraging (10).
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Conservation

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Like so many species the survival of the red-backed squirrel monkey is inextricably entwined with the future of the forests. Where there are protected reserves, there is hope for South America's wildlife (1). The largest single population of the subspecies Saimiri oerstedii citrinellus occurs in the Manuel Antonio National Park in Panama. However this park is only 683 hectares in size (1). A recent survey (2003) did, however, indicate that the total population size for the red-backed squirrel monkey is significantly larger than had been previously estimated, numbering between 1300 and 1780 individuals (6). It will be extremely important to monitor and protect the remaining populations in the future, and find ways of securing their survival (8).
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Description

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This small monkey has a slender body and a tail that is longer than the body itself. The tail is not prehensile, but it does aid in balance as this monkey leaps between branches in a squirrel-like fashion. The limbs are fairly long and slender, and the thighs are shorter in relation to the lower leg than in species that clamber, such as howler monkeys. This adaptation allows squirrel monkeys to exert more force when jumping and so they can propel themselves further (4). This monkey's fur is short, thick and yellow brown in colour, with the underside being a paler yellow. As its common name, the red-backed squirrel monkey suggests, this primate has red-coloured fur on its back (5). It also bears a distinctive crown on its head; in the black-crowned subspecies (Saimiri oerstedii oerstedii), this crown is, as the name suggests, black, whereas in the grey-crowned Central American squirrel monkey (Saimiri oerstedii citrinellus) it is agouti in the male, and blackish-grey in the female (2) (4). Males and females are similar in appearance, though males are slightly larger in size. During the breeding season males also become 'fatted', with a noticeable increase in size around the neck and shoulders (4).
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Habitat

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This species mainly lives in lowland scrub forest (2), although it also inhabits humid tropical forest, mature upland forest, river edge and mangrove forest (1).
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Range

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The black crowned subspecies has a restricted range along the Pacific coast of the Puntarenas province in south-western Costa Rica, and in Chiriqui and Veraguas provinces, northwestern Panama (2). The grey crowned subspecies is found in south-western Costa Rica where it has an even more restricted range, of only 210 km², on the Pacific coastal forests of Quepos (1).
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Status

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Classified as Endangered (EN B1ab (i, ii, iii)) on the IUCN Red List 2003 (1) and listed on Appendix I of CITES (3). This species has two subspecies: the black-crowned Central American squirrel monkey, Saimiri oerstedii oerstedii, is classified as Endangered (EN B1ab (i, ii, iii)) and the grey-crowned Central American squirrel monkey, Saimiri oerstedii citrinellus, is classified as Critically Endangered (CR B1ab (i, ii, iii)) (1).
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Threats

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The grey-crowned subspecies Saimiri oerstedii citrinellus is critically endangered and has lost 89% of its original habitat in Costa Rica, with the remaining range (just 210km²) being severely fragmented (1). This is due to widespread logging and clearing for cattle ranches which started during the 1950s. Large areas were also planted with African oil palms and rice. In Panama, the black-crowned subspecies Saimiri oerstedii oerstedii has also suffered habitat losses of 76%, and now occurs in fragmented forest areas throughout its range (1,166km²) (1).
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Primate Factsheets: Squirrel monkey (Saimiri)

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Webpage from Primate Info Net on this genus. Includes info on taxonomy, morphology, ecology, behavior, and conservation.

Red-backed or Central American squirrel monkey (Saimiri oerstedii)

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The binomial name Saimiri oerstedii was given by Johannes Theodor Reinhardt to honour his fellow Danish biologist Anders Sandøe Ørsted. The red-backed squirrel monkey occurs along the Pacific coast of Costa Rica and Panama inland to altitudes of up to 500 m asl. (28,31,32,38), being restricted to the northwest tip of Panama near the border with Costa Rica and the central and southern Pacific coast of Costa Rica, primarily in Manuel Antonio and Corcovado National Parks [8]. It is the only species of squirrel monkey occurring outside South America [5]. Some people think squirrel monkeys lived in Colombia in the late Miocene or Pliocene and migrated to Central America, becoming the ancestors of the red-backed species. Passage through the isthmus of Panama later closed due to rising oceans, and eventually opened up to another wave of migration @ 2 million years ago, when ancestors of modern populations of monkeys out-competed the earlier migrants, leading to the small range of the red-backed squirrel monkey [19]. The red-backed species was thought to be a a population of a South American species of squirrel monkey brought to Central America by humans. Evidence included the very small range of the red-backed species and the large gap from the range of other species. Nuclear and mitochondrial DNA showed tht the red-backed squirrel monkey is a separate species that apparently diverged from the South American species 260,000 to over 4 million years ago.[3] The squirrel lives mainly in lowland scrub forest, but also inhabits humid tropical forest, mature upland forest, river edge and mangrove forest (22). It prefers seasonally inundated forests, forest, floodplain, secondary forests and primary forests which have been partially logged [12]. It needs forests with abundant low and mid-level vegetation and has difficulty surviving in tall, mature, undisturbed forests that lack such vegetation [8,12,42]. In general, squirrel monkeys are arboreal and can be found in primary and secondary forests (38), thickets, and mangrove swamps (52). They are also found in cultivated areas, usually around streams (38). Saimiri oerstedii is known to inhabit humid Pacific slope forests (28). This small monkey has a slender body. Adults are 225-295 mm long, excluding the 362-465 mm tail, and weigh 500-1,100 g [5,8,28,39]; males weigh @ 750-950 g and females 600-800 g (5). The tail is not fully prehensile, but aids balance as the monkey leaps between branches like a squirrel [10,11]. The limbs are long and slender and the thighs are shorter in relation to the lower leg than in monkeys that clamber. This adaptation lets squirrel monkeys exert more force when jumping, so they can propel themselves further (24). The fur is short, thick and yellow brown, with the underside being white or pale yellow and with red, golden-red or orange fur on the back (25,28,40), olive shoulders, hips and tail, a black cap on top of the head [39], a white face with black rims around the eyes and black around the nose and mouth [7,8], orange hands and feet and a black tail tip. Males and females are similar, but males are 16% larger and generally have lighter caps than females [5]. In the breeding season males become 'fatted', becoming larger around the neck and shoulders (24). Squirrel monkeys have the largest brains of all primates relative to body size; the red-backed squirrel monkey's brain weighs about 25.7 g or @ 4% of its body weight [7,9]. The monkey is active by day and is arboreal (26). It usually walks and runs through the trees on all fours [7]. It lives in groups of 20-75 with several adult males, adult females and juveniles [5,12,43,46,47]. Groups above 100 are thought to be temporary mergers of two groups [2]. On average, groups contain about 60% more females than males [5]. The monkey has an egalitarian social structure; neither males nor females are dominant over each other [5]. Females do not form dominance hierarchies or coalitions [2,5]. There is no evidence of coalition formation in social interactions. Males in a group tend to be related to each other, so tend to form strong affiliations, only forming dominance hierarchies in the breeding season [5,15]. This is especially the case among males of the same age [12]. Groups have a home range of 35-63 hectares [12], which can overlap, especially in large, protected areas rather than more fragmented areas[12]. Groups can travel 2.5-4.2 km a day [13,26,29]. They do not split into separate foraging groups during the day. Individuals may separate from the main group to engage in different activities for periods of time, so the group may be dispersed over an area of up 1.2 hectares at any given time [14]. The group tends to sleep in the same trees every night for months at a time [14]. Groups generally do not compete or fight with each other [2]. The monkey is noisy. It makes many squeals, whistles and chirps[8]. It travels through the forest noisily, while disturbing vegetation [8]. It has four main calls: a "smooth chuck", "bent mask chuck", "peep" and "twitter".[7] There is little competition or agonistic interactions between groups. The squirrel monkey rarely associates with the white-headed capuchin. Its food occurs in smaller, more dispersed patches than with South American species, so associating with capuchins would impose higher foraging costs. While male white-headed capuchins are alert to predators, they devote more attention to detecting rival males than to detecting predators, and relatively less time to detecting predators than their South American counterparts. Associating with capuchins provides less predator detection benefits and imposes higher foraging costs on the red-backed squirrel monkey than on South American species [5,11,16,17]. Some bird species associate with the red-backed squirrel monkey. They follow monkeys to try and prey on insects and small vertebrates that the monkeys flush out, especially in the wet season, when arthropods are harder to find [12]. The monkey is omnivorous and spends most of the morning and afternoon foraging through the lower and middle levels of the forest (mainly the lower canopy and understory), typically at 4.5-9 m high.[12,14], but may travel at other levels. It eats berries and other fruits, nuts, seeds, leaves, buds, flower nectar, gums and other plant materials, invertebrates (especially grasshoppers and caterpillars) and small vertebrates [4,27,28,38,41,43,44]. Nearly half of the diet is made up of fruit [4]. It has difficulty finding its desired food late in the wet season, when fewer arthropods are available [8]. It is said to recognise the folded leaf-tents made by some fruit-eating bats, attacking them to extract roosting bats (28). When it finds a bat it climbs to a higher level and jumps onto the tent from above, trying to dislodge the bat. If the fallen bat doesn't fly away in time, the monkey pounces on it on the ground and eats it [12]. The fruits the monkey typically exploits occur in small and very scarce patches; feeding competition is very low. In the dry season shortages of appropriate fruiting trees means it may depend entirely on animal prey (45). The monkey is an important seed disperser and a pollinator of passion flowers and other flowers [12]. It is not a significant agricultural pest, but may eat corn, coffee, bananas, mangos and other fruits[12,14]. When monkeys find food in a tree, they often do not completely use up the resources available and may return to it later (6). Predators include birds of prey, cats and constricting and venomous snakes [5]. The oldest males show high levels of vigilance for predators and bear most responsibility for detecting them [2,12]. When a monkey detects a raptor, it gives a high-pitched alarm peep and dives for cover, as do other monkeys that hear the alarm call. The monkeys are very cautious about raptors and give alarms when they detect any raptor-like object, including small airplanes, falling branches and large leaves [14]. Raptors spend much more time near monkey troops when infants are born and prey on many of the newborn infants. Other predators include toucans, tayras, opossums, coatis and spider monkeys [14]. Reproduction is seasonal, seldom exceeding two months in duration in the dry season (51). Mating occurs in September [12] or January and February. All females enter oestrus at about the same time. A month or two before the breeding season begins, males become larger, due to altered water balance within the body. This is caused by converting the male hormone testosterone into oestrogen; the more testosterone he produces, the more he grows before the breeding season. Reproductively mature males collaborate in mobbing females in the mating season. As males in a group have not been seen fighting over access to females in the breeding season, nor trying to force females to copulate with them, it is thought that female choice determines which males get to breed with females. Females tend to prefer males that expand the most in advance of breeding season. This may be because the most enlarged males are generally the oldest and most effective at detecting predators or it may be due to runaway intersexual selection [14]. Males may leave their group for short periods of time in the breeding season to try to mate with females from neighboring groups. Females are receptive to males from other groups, but resident males try to repel intruders. Mating usually occurs during the dry season. In S. oerstedii, sexual receptivity in females is synchronized, lasting perhaps 12-36 hours a season [50]. Single births occur after 6-7 months at night and during wet season, the period of greatest food availability, within a single week in February and March [5,6,12,14,28], so there is enough food for mothers and their young and less time is spent foraging (30). The infant has a fully prehensile tail [10,11]. It depends on its mother for about one year [12]. The mother takes care of the young, which rides on her back and nurses, with little attention paid to it by the group members (6), but other females ('aunts') may help (6). During its third and fourth weeks of life, the infant begins to move around more and between weeks five and ten, it occasionally disembarks from its mother's back, explores the nearby area, and starts to eat solid foods (6). Over the next few months, contacts with the mother become less frequent (6). Social play probably first occurs @ 2 months (6) and helps separate the infant from its mother (52). In the first year of life, the young monkeys engage in social play with each other, usually in the form of fighting games (6). Females give birth every 12 months [48,53], so the prior infant becomes independent at about the same time the new infant is born. Only 50% of infants survive over 6 months, largely due to predation by birds [5]. Females do not resume cycling until their infant either dies or is weaned (4). Females become adult at 12-13 months and sexually mature at 1-2.5 years old; males become sexually mature at 4-6 years old [5,6]. Females leave their natal group on reaching sexual maturity; males usually stay with their group for their entire lives [5]. Males of the same age tend to associate with each other in age cohorts. On reaching sexual maturity, an age cohort may choose to leave the group and try to oust the males from another group to attain increased reproductive opportunities [5]. Captive can live over 15-18 years [12,55]; other species may live over 20 years.[5] The monkey was classified as Endangered on the IUCN Red List 2003 (2,22,38) and is listed on Appendix I of CITES (23). The population declined steeply after the 1970s, probably due to deforestation for agriculture and logging, hunting and capture to be kept as pets; its fragmented range encompasses 8,000 square km [18,38]. In 2008 the International Union for Conservation of Nature (IUCN) upgraded its conservation status from "endangered" to "vulnerable"; it is abundant in the areas it inhabits [4]. Its survival is entwined with the future of the forests (22). A survey in 2003 showed that the total population size (1300-1780) is significantly larger than previous estimates (26,28). The population density is estimated at 36 monkeys per square kilometre in Costa Rica and 130 in Panama.[13] It has been estimated that the population of the Central American squirrel monkey has been reduced from about 200,000 in the 1970s to less than 5000 [18]. There are significant efforts within Costa Rica to try to preserve this monkey from extinction.[20] A reforestation project within Panama tries to preserve the vanishing population of the Chiriqui Province.[21] There are two subspecies [1]. The black-crowned Central American squirrel monkey (Saimiri oerstedii oerstedii) lives in the Chiriqui and Veraguas provinces, on the Pacific coast of northwest Panama and the coast of the Puntarenas province and Osa Peninsula area of south-west Costa Rica (including Corcovado National Park) (28,29,31-34). It lives at 0-500 m above sea level (31). It has a black crown and more yellowish limbs and underparts [3]. In Panama, it has suffered habitat losses of 76% and now occurs in fragmented forest areas throughout its range (1,166km²) (22). It is Endangered. The grey-crowned Central American squirrel monkey (Saimiri oerstedii citrinellus) lives in the Quepos forests in the Central Pacific portion of south-west Costa Rica [22,26,35], up to 500 m above sea level. In 2003, the remaining wild population was estimated to be 1300-1800 individuals [2] in a restricted, severely fragmented range of 210 km² [22,36,37]. The male has an agouti crown; the crown is blackish-grey in the female (24). It is Critically Endangered and has lost 89% of its original habitat, due to widespread logging and clearing for cattle ranches which started during the 1950s. Large areas were planted with African oil palms and rice. The largest single population occurs in the Manuel Antonio National Park in Panama (22). The total number is up to 1300-1800 individuals (26,32,37).
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Central American squirrel monkey

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The Central American squirrel monkey (Saimiri oerstedii), also known as the red-backed squirrel monkey, is a squirrel monkey species from the Pacific coast of Costa Rica and Panama. It is restricted to the northwestern tip of Panama near the border with Costa Rica, and the central and southern Pacific coast of Costa Rica, primarily in Manuel Antonio and Corcovado National Parks.

It is a small monkey with an orange back and a distinctive white and black facial mask. It has an omnivorous diet, eating fruits, other plant materials, invertebrates and some small vertebrates. In turn, it has a number of predators, including raptors, cats and snakes. It lives in large groups that typically contain between 20 and 75 monkeys. It has one of the most egalitarian social structures of all monkeys. Females do not form dominance hierarchies, and males do so only at breeding season. Females become sexually mature at 2+12 years, and males at 4 to 5 years. Sexually mature females leave the natal group, but males can remain with their natal group their entire life. The Central American squirrel monkey can live for more than 15 years.

The Central American squirrel monkey population declined precipitously after the 1970s. This decline is believed to be caused by deforestation, hunting, and capture to be kept as pets. Efforts are underway to preserve the species.

Taxonomy

The Central American squirrel monkey is a member of the family Cebidae, the family of New World monkeys containing squirrel monkeys, capuchin monkeys, tamarins and marmosets. Within the family Cebidae, it is a member of the subfamily Saimiriinae, the subfamily containing squirrel monkeys.[5] It is one of five recognized species of squirrel monkey, and the only species occurring outside South America.[6] The Central American Squirrel Monkey is placed in genus Saimiri (Voigt, 1831) along with all the other squirrel monkey species. Among the squirrel monkeys, the Central American squirrel monkey is most closely related to the Guianan squirrel monkey (Saimiri sciureus) and the bare-eared squirrel monkey (Saimiri ustus) and these three species form the S. sciureus species group.[7][8] The binomial name Saimiri oerstedii was given by Johannes Theodor Reinhardt in honor of his fellow Danish biologist Anders Sandøe Ørsted.

There are two subspecies of the Central American squirrel monkey:[1]

S. o. oerstedii lives in the western Pacific portion of Panama and the Osa Peninsula area of Costa Rica (including Corcovado National Park), while S. o. citrinellus lives in the Central Pacific portion of Costa Rica. The largest estimate (most recently in 2003) is that the remaining wild population of S. o. citrinellus is only 1,300 to 1,800 individuals.[2]

Physical description

The Central American squirrel monkey differs in coloration from South American squirrel monkeys. While South American squirrel monkeys tend to be primarily greenish in color, the Central American species has an orange back with olive shoulders, hips and tail, and white undersides. The hands and feet are also orange. There is a black cap at the top of the head, and a black tip at the end of the tail. Males generally have lighter caps than females. The face is white with black rims around the eyes and black around the nose and mouth.[9][10]

Body coloration

The two subspecies are similar in coloration, but differ in the shade of the cap. The northern subspecies, living in Central Pacific Costa Rica, has a lighter cap than the southern subspecies, which lives in Panama and in parts of Costa Rica near Panama.[10] The southern subspecies also has more yellowish limbs and underparts.[4]

Adults reach a length of between 266 and 291 millimetres (10+12 and 11+12 inches), excluding tail, and a weight between 600 and 950 grams (21 and 34 ounces).[6][10] The tail is longer than the body, and between 362 and 389 mm (14+14 and 15+38 in) in length.[10] As with other squirrel monkeys, there is considerable sexual dimorphism. On average, males weigh 16% more than females.[6] Males have an average body weight of 829 g (29+14 oz) and females average 695 g (24+12 oz).[6] Squirrel monkeys have the largest brains of all primates relative to their body size; the Central American squirrel monkey's brain weighs about 25.7 g (2932 oz), or about 4% of its body weight.[9][11] Unlike larger relatives, such as the capuchin, spider and howler monkeys, Central American squirrel monkeys do not have a fully prehensile tail, except as newborn infants, and the tail is primarily used to help with balance.[12][13]

Behavior

Social structure

The Central American squirrel monkey is arboreal and diurnal, and most often moves through the trees on four legs (quadrupedal locomotion).[9] It lives in groups containing several adult males, adult females, and juveniles. The group size tends to be smaller than that of South American squirrel monkeys, but is still larger than for many other New World monkey species. The group generally numbers between 20 and 75 monkeys, with a mean of 41 monkeys.[6][14] Groups in excess of 100 sometimes occur, but these are believed to be temporary mergers of two groups.[2] On average, groups contain about 60% more females than males.[6]

Resting on a branch

The squirrel monkey groups have a home range of between 35 and 63 hectares (86 and 156 acres).[14] Group ranges can overlap, especially in large, protected areas such as Manuel Antonio National Park. Less overlap occurs in more fragmented areas.[14] Groups can travel between 2,500 and 4,200 m (8,200 and 13,800 ft) per day.[15] Unlike some other monkey species, the group does not split into separate foraging groups during the day. Individual monkeys may separate for the main group to engage in different activities for periods of time, and thus the group may be dispersed over an area of up to 1.2 hectares (3 acres) at any given time.[16] The group tends to sleep in the same trees every night for months at a time, unlike other squirrel monkeys.[16]

There are no dominance hierarchies among the females, and the females do not form coalitions.[2][6] Males in the group are generally related to each other and thus tend to form strong affiliations, and only form dominance hierarchies during the breeding season.[6] This is especially the case among males of the same age.[14] Neither males nor females are dominant over each other, an egalitarian social system that is unique to Central American squirrel monkeys. In South American species, either the females (S. boliviensis) or males (S. sciureus) are dominant over the other sex, and both sexes form stable dominance hierarchies.[6] Groups of Central American squirrel monkeys generally do not compete or fight with each other.[2] Male Costa Rican squirrel monkeys are known to have very close bonds with each other.[17]

Although South American species of squirrel monkeys often travel with and feed together with capuchin monkeys, the Central American squirrel monkey only rarely associates with the white-headed capuchin. This appears to be related to the fact that the food the Central American squirrel monkey eats is distributed in smaller, more dispersed patches than that of South American squirrel monkeys. As a result of the different food distribution, associating with capuchin monkeys would impose higher foraging costs for the Central American squirrel monkey than for their South American counterparts. In addition, while male white-headed capuchins are alert to predators, they devote more attention to detecting rival males than to detecting predators, and relatively less time to detecting predators than their South American counterparts. Therefore, associating with capuchins would provide less predator detection benefits and impose higher foraging costs on the Central American squirrel monkey than on South American squirrel monkeys.[6][13][18][19] An alternative explanation is that capuchin groups are larger than squirrel monkey groups in Central America, but in South America the squirrel monkey groups are larger.[20]

In one study a slight tendency was observed in which Central American squirrel monkeys were more likely to travel near mantled howler monkeys if the howlers were vocalizing loudly within their home range, but no physical contact or obvious social interaction was observed.[20] Variegated and red-tailed squirrels may join Central American monkey groups without eliciting a reaction from the monkeys.[20]

Certain bird species associate with the Central American squirrel monkey. The birds follow the monkeys in an attempt to prey on insects and small vertebrates that the monkeys flush out. At Corcovado National Park, bird species known to regularly follow squirrel monkeys include the double-toothed kite, the grey-headed tanager and the tawny-winged woodcreeper, but other woodcreepers and such species as motmots and trogons do so as well. This activity increases during the wet season, when arthropods are harder to find.[14]

Diet

The Central American squirrel monkey is omnivorous. Its diet includes insects and insect larvae (especially grasshoppers and caterpillars), spiders, fruit, leaves, bark, flowers, and nectar. It also eats small vertebrates, including bats, birds, lizards, and tree frogs. It finds its food foraging through the lower and middle levels of the forest, typically between 4.5 and 9 metres (15 and 30 feet) high.[14][16] Two-thirds to three-quarters of each day is spent foraging for food. It has difficulty finding its desired food late in the wet season, when fewer arthropods are available.[10]

It has a unique method of capturing tent-making bats. It looks for roosting bats by looking for their tents (which are made of a folded leaf). When it finds a bat it climbs to a higher level and jumps onto the tent from above, attempting to dislodge the bat. If the fallen bat does not fly away in time, the monkey pounces on it on the ground and eats it.[14]

The Central American squirrel monkey is an important seed disperser and a pollinator of certain flowers, including the passion flower.[14] While it is not a significant agricultural pest, it does sometimes eat corn, coffee, bananas and mangos.[14] Other fruits eaten include cecropias, legumes, figs, palms, cerillo, quiubra, yayo flaco and wild cashew fruits.[14][16]

Communication

The Central American squirrel monkey is noisy. It makes many squeals, whistles and chirps.[10] It also travels through the forest noisily, disturbing vegetation as it moves through.[10] It has four main calls, which have been described as a "smooth chuck", a "bent mask chuck", a "peep" and a "twitter".[9]

Predators

Predators of the Central American squirrel monkey include birds of prey, cats and snakes. Constricting and venomous snakes both prey on squirrel monkeys. Raptors are particularly effective predators of Central American squirrel monkeys.[6] The oldest males bear most of the responsibility for detecting predators.[2][14] When a Central American squirrel monkey detects a raptor, it gives a high-pitched alarm peep and dives for cover. All other squirrel monkeys that hear the alarm call also dive for cover. The monkeys are particularly cautious about raptors, and give alarms when they detect any raptor-like object, including small airplanes and even falling branches and large leaves.[16]

Predator detection by males becomes particularly important during the period when the infants are born. Raptors spend significantly more time near the squirrel monkey troops during this period, and prey on a significant number of newborn infants. Other animals that prey on Central American squirrel monkey infants include toucans, tayras, opossums, coatis, snakes, and even spider monkeys.[16]

Reproduction

Two-month-old infant riding on mother's back

The breeding season for the Central American squirrel monkey is in September.[14] All females come into estrus at virtually the same time. A month or two before the breeding season begins, males become larger. This is not due to extra muscle, but to altered water balance within the male's body. This is caused by the conversion of the male hormone testosterone into estrogen; thus the more testosterone a male produces, the more he grows in advance of the breeding season. Since males within a group have not been observed fighting over access to females during the breeding season, nor attempting to force females to copulate with them, it is believed that female choice determines which males get to breed with females. Females tend to prefer the males that expand the most in advance of breeding season. This may be because the most enlarged males are generally the oldest and the most effective at detecting predators, or it may be a case of runaway intersexual selection.[16]

Males sometimes leave their group for short periods of time during the breeding season in order to try to mate with females from neighboring groups. Females are receptive to males from other groups, although resident males attempt to repel the intruders. The gestation period is six months, and the infants are born within a single week during February and March. Typically, a single infant is born.[6][14][16]

Only 50% of infants survive more than six months, largely due to predation by birds.[6] The infant remains dependent on its mother for about one year.[14] Females give birth every 12 months, so the prior infant becomes independent at about the same time the new infant is born. Females become sexually mature at 2+12 years old, while males become sexually mature at between 4 and 5 years old.[6] The females leave their natal group upon reaching sexual maturity, while males usually remain with their group for their entire lives. This is different from South American squirrel monkey species, where either males disperse from their natal group or both sexes disperse.[6] Males of the same age tend to associate with each other in age cohorts. Upon reaching sexual maturity, an age cohort may choose to leave the group and attempt to oust the males from another group in order to attain increased reproductive opportunities.[6]

The lifespan of the Central American squirrel monkey in the wild is unknown, but captive specimens have been known to live more than 15 years.[14] Other squirrel monkey species are known to be able to live more than 20 years.[6]

Distribution and habitat

The Central American squirrel monkey has a restricted distribution in Costa Rica and Panama. It lives only near the Pacific coast. Its range covers Central Pacific Costa Rica in the north through western Panama.[10] It lives in two of Costa Rica's national parks—Manuel Antonio National Park and Corcovado National Park—where it can be seen by visitors, but it is not as commonly seen in these parks as the white-headed capuchin or the mantled howler monkeys.[21] It lives in lowland forests and is restricted to secondary forests and primary forests which have been partially logged.[14] It requires forests with abundant low and mid-level vegetation and has difficulty surviving in tall, mature, undisturbed forests that lack such vegetation.[10][14] Its specialization for coastal lowland forest may explain its restricted distribution.[8]

Conservation status

It was once believed that the Central American squirrel monkey was just a population of a South American species of squirrel monkey brought to Central America by humans. Evidence for this theory included the very small range of the Central American squirrel monkey and the large gap from the range of any other squirrel monkey species. A study of nuclear and mitochondrial DNA demonstrated that the Central American squirrel monkey is indeed a separate species that apparently diverged from the South American species long ago – at least 260,000 years ago and possibly more than 4 million years ago.[4] A genetic study by Lynch Alfaro, et al. in 2015 estimated that the Central American squirrel monkey diverged from S. scuireus a little less than 1 million years ago.[8]

On a balcony of a hotel near Manuel Antonio National Park, Costa Rica

One popular theory is that squirrel monkeys did live in Colombia during the late Miocene or Pliocene and these squirrel monkeys migrated to Central America, becoming the ancestors of the current Central American species. According to this theory, the Guatemalan black howler migrated to Central America around the same time. Passage through the isthmus of Panama later closed due to rising oceans, and eventually opened up to another wave of migration about 2 million years ago. These later migrants, ancestors to modern populations of white-headed capuchins, mantled howlers and Geoffroy's spider monkeys, out-competed the earlier migrants, leading to the small range of the Central American squirrel monkey and Guatemalan black howler.[22] Ford suggested that high water levels during the Pleistocene not only cut off the Central American squirrel monkey from other squirrel monkeys, but was also responsible for the formation of two subspecies.[8][22] Lynch Alfaro, et al. suggested that the separation of the Central American squirrel monkey from other squirrel monkeys may have resulted from a period of high aridity in northern South America.[8]

The population density has been estimated at 36 monkeys per square kilometer (93 per square mile) in Costa Rica and 130 monkeys per square kilometer (337 per square mile) in Panama.[15] It has been estimated that the population of the Central American squirrel monkey has been reduced from about 200,000 in the 1970s to less than 5,000.[21] This is believed to be largely due to deforestation, hunting, and capture for the pet trade.[21] There are significant efforts within Costa Rica to try to preserve this monkey from extinction.[23] A reforestation project within Panama tries to preserve the vanishing population of the Chiriqui Province.[24]

As of 2021, the Central American squirrel monkey is listed as endangered from a conservation standpoint by the IUCN.[2] This is due mainly to deforestation ongoing habitat loss, but other sources such as capture for the pet trade also contribute.[2]

References

  1. ^ a b Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Baltimore: Johns Hopkins University Press. pp. 138–139. ISBN 0-801-88221-4. OCLC 62265494.
  2. ^ a b c d e f g h Solano-Rojas, D. (2021). "Saimiri oerstedii". IUCN Red List of Threatened Species. 2021: e.T19836A17940807. doi:10.2305/IUCN.UK.2021-1.RLTS.T19836A17940807.en. Retrieved 11 March 2022.
  3. ^ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
  4. ^ a b c Rylands, A.; Groves, C.; Mittenmeier, R.; Cortes-Ortiz, L. & Hines, J. (2006). "Taxonomy and Distributions of Mesoamerican Primates". In Estrada, A.; Garber, P.; Pavelka, M. & Luecke, L. (eds.). New Perspectives in the Study of Mesoamerican Primates. New York: Springer. pp. 37–39. ISBN 978-0-387-25854-6.
  5. ^ Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Baltimore: Johns Hopkins University Press. pp. 138–139. ISBN 0-801-88221-4. OCLC 62265494.
  6. ^ a b c d e f g h i j k l m n o p q Jack, K. (2007). "The Cebines". In Campbell, C.; Fuentes, A.; MacKinnon, K.; Panger, M.; Bearder, S. (eds.). Primates in Perspective. The Oxford University Press. pp. 107–120. ISBN 978-0-19-517133-4.
  7. ^ Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Baltimore: Johns Hopkins University Press. pp. 138–139. ISBN 0-801-88221-4. OCLC 62265494.
  8. ^ a b c d e Lynch Alfaro, J.W.; et al. (2015). "Biogeography of squirrel monkeys (genus Saimiri): South-central Amazon origin and rapid pan-Amazonian diversification of a lowland primate". Molecular Phylogenetics and Evolution. 82: 436–454. doi:10.1016/j.ympev.2014.09.004. PMID 25305518.
  9. ^ a b c d Rowe, N. (1996). The Pictorial Guide to the Living Primates. Pogonias Press. p. 98. ISBN 978-0-9648825-0-8.
  10. ^ a b c d e f g h i Emmons, L. (1997). Neotropical Rainforest Mammals A Field Guide (Second ed.). The University of Chicago Press. pp. 126–127. ISBN 978-0-226-20721-6.
  11. ^ "Squirrel Monkey". Rainforest Alliance. Retrieved 2008-10-18.
  12. ^ Sussman, R. (2003). Primate Ecology and Social Structure Volume 2: New World Monkeys (Revised First ed.). Pearson Custom Publishing. p. 76. ISBN 978-0-536-74364-0.
  13. ^ a b Fleagle, J. (1998). Primate Adaption and Evolution (Second ed.). Academic Press. pp. 157–160. ISBN 978-0-12-260341-9.
  14. ^ a b c d e f g h i j k l m n o p q Wainwright, M. (2002). The Natural History of Costa Rican Mammals. Zona Tropical. pp. 131–134. ISBN 978-0-9705678-1-9.
  15. ^ a b Sussman, R. (2003). Primate Ecology and Social Structure Volume 2: New World Monkeys (Revised First ed.). Pearson Custom Publishing. p. 86. ISBN 978-0-536-74364-0.
  16. ^ a b c d e f g h Boinski, S. (1992). "Monkeys with Inflated Sex Appeal". In Ciochon, R.; Nisbett, R. (eds.). The Primate Anthology. Prentice-Hall. pp. 174–179. ISBN 978-0-13-613845-7.
  17. ^ Boinski, S. (1994). "Affiliation Patterns among Male Costa Rican Squirrel Monkeys". Behaviour. 130 (3): 191–209. doi:10.1163/156853994X00523.
  18. ^ Boinski, S. (2000). "Social Manipulation Within and Between Troops Mediates Primate Group Movement". In Boinski, S.; Garber, P. (eds.). On the Move. The University of Chicago Press. pp. 447–448. ISBN 978-0-226-06340-9.
  19. ^ Boinski, S. (1989). "Why don't Saimiri oerstedii and Cebus capucinus form mixed-species groups?". International Journal of Primatology. 10 (2): 103–114. doi:10.1007/BF02736248. S2CID 24192169.
  20. ^ a b c Baldwin, J.D. (1985). "The Behavior of Squirrel Monkeys (Saimiri) in Natural Environments". In Rosenblum, L.A.; Coe, C.L. (eds.). Handbook of Squirrel Monkey Research. Plenum Press. pp. 49–50. ISBN 978-0306417542.{{cite book}}: CS1 maint: ignored ISBN errors (link)
  21. ^ a b c Hunter, L.; Andrew, D. (2002). Watching Wildlife Central America. Lonely Planet Publications. pp. 100, 148. ISBN 978-1-86450-034-9.
  22. ^ a b Ford, S. (2006). "The Biographic History of Mesoamerican Primates". In Estrada, A.; Garber, P.A.; Pavelka, M.S.M.; Luecke, L. (eds.). New Perspectives in the Study of Mesoamerican Primates. New York: Springer. pp. 100–107. ISBN 978-0-387-25854-6.
  23. ^ "Save the Mono Titi Manuel Antonio Costa Rica". ASCOMOTI. Archived from the original on April 3, 2009. Retrieved 2008-05-12.
  24. ^ "The Rainforest Returns". Saimiri Wildlife. Archived from the original on 2008-05-07. Retrieved 2008-10-25.

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Central American squirrel monkey: Brief Summary

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The Central American squirrel monkey (Saimiri oerstedii), also known as the red-backed squirrel monkey, is a squirrel monkey species from the Pacific coast of Costa Rica and Panama. It is restricted to the northwestern tip of Panama near the border with Costa Rica, and the central and southern Pacific coast of Costa Rica, primarily in Manuel Antonio and Corcovado National Parks.

It is a small monkey with an orange back and a distinctive white and black facial mask. It has an omnivorous diet, eating fruits, other plant materials, invertebrates and some small vertebrates. In turn, it has a number of predators, including raptors, cats and snakes. It lives in large groups that typically contain between 20 and 75 monkeys. It has one of the most egalitarian social structures of all monkeys. Females do not form dominance hierarchies, and males do so only at breeding season. Females become sexually mature at 2+1⁄2 years, and males at 4 to 5 years. Sexually mature females leave the natal group, but males can remain with their natal group their entire life. The Central American squirrel monkey can live for more than 15 years.

The Central American squirrel monkey population declined precipitously after the 1970s. This decline is believed to be caused by deforestation, hunting, and capture to be kept as pets. Efforts are underway to preserve the species.

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cc-by-sa-3.0
copyright
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